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Sunday, August 11, 2019

Psychology of eating meat

From Wikipedia, the free encyclopedia
 
The psychology of eating meat is a complex area of study illustrating the confluence of morality, emotions, cognition, and personality characteristics. Research into the psychological and cultural factors of meat eating suggests correlations with masculinity; support for hierarchical values; and reduced openness to experience. Because meat eating is widely practiced but is sometimes associated with ambivalence, it has been used as a case study in moral psychology to illustrate theories of cognitive dissonance and moral disengagement. Research into the consumer psychology of meat is relevant both to meat industry marketing and to advocates of reduced meat consumption.

Consumer psychology

Many factors affect consumer choices about meat, including price, appearance, and source information
 
Meat is an important and highly preferred human food. Individuals' attitudes towards meat are of interest to consumer psychologists, to the meat industry, and to advocates of reduced meat consumption. These attitudes can be affected by issues of price, health, taste, and ethics. The perception of meat in relation to these issues affects meat consumption.

Meat is traditionally a high-status food. It may be associated with cultural traditions and has strong positive associations in most of the world. However, it sometimes has a negative image among consumers, partly due to its associations with slaughter, death, and blood. Holding these associations more strongly may decrease feelings of pleasure from eating meat and increase disgust, leading to lowered meat consumption. In the West, these effects have been found to be particularly true among young women. Negative associations may only cause consumers to make meat less noticeable in their diets rather than reducing or eliminating it, for example making meat an ingredient in a more-processed dish. It has been suggested that this is the result of a disconnect between individuals' roles as consumers and as citizens.

Implicit attitudes towards meat have been reported to vary significantly between omnivores and vegetarians, with omnivores holding much more positive views. Vegetarians may express either revulsion or nostalgia at the thought of eating meat.

Consumer behavior towards meat may be modeled by distinguishing the effects of intrinsic factors (properties of the physical product itself, such as color) and extrinsic factors (everything else, including price and brand).

Intrinsic factors

Taste and texture are self-reported to be important factors in food choice, although this may not accurately reflect consumer behavior. Consumers describe meat as "chewy", "tender", and "rich". In the United Kingdom, meat is traditionally considered to taste good. People experience the taste and texture of meat in significantly different ways, with variations across ages, genders, and cultures. Tenderness is perhaps the most important of all factors impacting meat eating quality, with others being flavor, juiciness, and succulence.

Visual appearance is one of the primary cues consumers use to assess meat quality at the point of sale, and to select meats. Color is one of the most important characteristics in this context. Different cultural traditions lead consumers to prefer different colors: some countries prefer relatively dark pork overall, some light, and some have no clear preference.

Visible fat content and marbling are also important intrinsic quality cues. Consumers as a whole tend to prefer leaner beef and pork, although significant variations exist across geographical regions. Marbling is important to some consumers but not others, and, as for fat content more generally, preference for marbling varies by region.

Extrinsic factors

Price is an important extrinsic factor which can affect consumer choices about meat. Price concerns may induce consumers to choose among different meats, or avoid meat altogether.

Health concerns are also relevant to consumer choices about meat. The perceived risk of food contamination can affect consumer attitudes towards meat, as after meat-related scares such as those associated with mad cow disease or bird flu. Safety-related product recalls can impact demand for meat. People may reduce or eliminate meat from their diets for perceived health benefits. Health considerations may motivate both meat-eaters and vegetarians. Meatless diets in adolescents can be a way to conceal eating disorders, although vegetarianism does not necessarily increase the risk of disordered eating.

Research suggests consumers tend to prefer meats whose origin lies in their own country over imported products, partly due to the fact that domestic meats are perceived to be of higher quality. This effect may also reflect consumers' ethnocentrism or patriotism. The importance of meat's country of origin varies from country to country.

Beliefs and attitudes about environmental and animal welfare concerns can affect meat consumption. Consumers in the developed world may be willing to pay slightly more for meat produced according to higher animal welfare standards, although welfare and environmental concerns are usually considered less important than attributes more directly related to meat quality, such as appearance. A 2001 study in Scotland found that, although participants cared about animal welfare in general, they considered price and appearance more important than welfare when buying meat. A study of Dutch consumers found that both rational and emotional responses to environmental and other concerns affected purchasing of organic meat.

Meat consumption patterns can also be influenced by individuals' family, friends, and traditions. A study of British eating patterns found that meat was often associated with positive food traditions, such as the Sunday roast. Some consumers only purchase meat conforming with religious prescriptions, such as halal meat. These consumers' trust in quality assurance organizations, and individual relationships with meat providers, have been reported to significantly affect their purchasing behavior.

Recent trends in animal husbandry, such as biotechnology, factory farming, and breeding animals for faster growth, are expected to have a continuing effect on the evolution of consumer attitudes towards meat.

Meat paradox

One question examined in the psychology of eating meat has been termed the meat paradox: how can individuals care about animals, but also eat them? Internal dissonance can be created if people's beliefs and emotions about animal treatment do not match their eating behavior, although it may not always be subjectively perceived as a conflict. This apparent conflict associated with a near-universal dietary practice provides a useful case study for investigating the ways people may change their moral thinking to minimize discomfort associated with ethical conflicts.

The dissonance that arise out of the meat paradox generates a negative interpersonal state, which then motivates an individual to find the means to alleviate it. Recent studies in this area suggest that people can facilitate their practices of meat eating by attributing lower intelligence and capacity for suffering to meat animals, by thinking of these animals as more dissimilar to humans, by caring less about animal welfare and social inequality, and by dissociating meat products from the animals they come from.

Perceptions of meat animals

Pastured meat rabbits. Studies suggest that classifying animals as food can affect their perceived intelligence and moral standing.
 
Ethical conflicts arise when eating animals if they are considered to have moral status. Perceptions of animals' moral status vary greatly, but are determined in part by perceptions of animals as having conscious minds and able to experience pain, and their perceived similarity to humans. Some social psychologists hypothesize that meat eaters can reduce discomfort associated with the meat paradox by minimizing their perception of these morally relevant qualities in animals, particularly animals they regard as food, and several recent studies provide support for this hypothesis. It was found, for instance, that by simply being classified within the food animals group, an animal is immediately attributed fewer moral rights.

A 2010 study randomly assigned college students to eat beef jerky or cashews, then judge the moral importance and cognitive abilities of a variety of animals. Compared with students who were given cashews, those who ate beef jerky expressed less moral concern for animals, and assigned cows a diminished ability to have mental states that entail the capacity to experience suffering.

Subsequent studies similarly found that people were more inclined to feel it was appropriate to kill animals for food when they perceived the animals as having diminished mental capacities, a finding replicated in samples from the U.S., Canada, Hong Kong, and India; that, conversely, they perceived unfamiliar animals as having lesser mental capacities when told they were used as food; and, again, that eating meat caused participants to ascribe fewer mental abilities to animals over both the short and long term. Another study showed that rearing animals for slaughter led to less recognition of mental states in cows and sheep for those who expected to eat meat.

A 2014 review suggested that these phenomena could be explained as a set of dissonance reduction techniques used to reduce negative emotions associated with the meat paradox, but noted that the existence of such emotions had not been demonstrated. A 2016 review drew an analogy between the meat paradox and sexual objectification, writing that both practices involve strategically changing perceptions of others when thinking of them as potential "resources" (i.e., for meat or sex), and citing recent studies suggesting that sexually objectifying people prompts a reduction in their perceived humanness and moral importance.

Dissociation and avoidance

Several proposed strategies for resolving the meat paradox dissociate meat as a food product from the animals which produce it, or psychologically distance themselves from the processes of meat production. Although concern for animal welfare has recently increased in several countries, a trend towards dissociating meat from its animal origins has tended to prevent such concerns from influencing consumer behavior.

People in many cultures do not like to be reminded of the connection between animals and meat, and tend to "de-animalize" meat when necessary to reduce feelings of guilt or of disgust. Meat in Western countries is often packaged and served so as to minimize its resemblance to live animals, without eyes, faces, or tails, and the market share of such products has increased in recent decades; however, meat in many other cultures is sold with these body parts.

Some authors have suggested that the use of non-animal words such as "sirloin" and "hamburger" for meat can reduce the salience of meat's origins in animals, and in turn reduce perceived consumption of animals. Similarly, farmers and hunters use terms such as "processing" and "managing" rather than "killing", a choice which can be interpreted as a way to provide psychological distance and facilitate animal use.

The importance of dissociation processes was supported by a 2016 Norwegian study which, in a series of experiments, directly tested the effects of making live animals more salient.

In addition to dissociation, people who experience discomfort relating to the meat paradox may simply avoid confrontation of the issue. Cultural socialization mechanisms may also discourage people from thinking of their food choices as harmful; for example, children's books and meat advertisements usually portray farm animals as leading happy lives, or even desiring to be eaten. Compartmentalizing animals in different categories (such as pets, pests, predators, and food animals) may help avoid dissonance associated with differential treatment of different species.

Pro-meat attitudes

Affective factors, such as positive memories, influence meat consumption.
 
Ethical conflicts between enjoying meat and caring for animals may be made less problematic by holding positive attitudes towards meat. People who think of meat as safe, nutritious, and sustainable tend to experience less ambivalence about eating it. Religious belief in God-given dominion over animals can also justify eating meat.

A series of studies published in 2015 asked meat-eating American and Australian undergraduates to "list three reasons why you think it is OK to eat meat." Over 90% of participants offered reasons which the researchers classified among the "four N's":
  • Appeals to human evolution or to carnivory in nature ("natural")
  • Appeals to societal or historical norms ("normal")
  • Appeals to nutritive or environmental necessity ("necessary")
  • Appeals to the tastiness of meat ("nice")
The researchers found that these justifications were effective in reducing moral tension associated with the meat paradox.

Personality characteristics

Studies in personality trait psychology have suggested that individuals' values and attitudes affect the frequency and comfort with which they eat meat.

Those who value power more highly have been found in several studies to eat more meat, while those who prefer self-transcendence values tend to eat less. In particular, studies have found that the personality trait of openness to experience is negatively correlated with meat consumption, and that vegetarians and pesco-vegetarians have more open personalities.

Other research has indicated that meat consumption is correlated with support for hierarchy and inequality values. Those with a social dominance orientation, who more strongly support inequality and hierarchical structures, have been found in some studies to eat more meat; it has been suggested that this is consistent with their preference for having certain groups dominate others (in this case, having humans dominate animals). In addition, research suggests people self-identifying as greater meat eaters have greater right-wing authoritarianism and social dominance orientation. Dhont & Hodson (2014) suggested that this subconsciously indicates their acceptance of cultural tradition, and their rejection of nonconformist animal rights movements.

Many of these personality characteristics have been shown to relate with moral disengagement in meat consumption. In particular, individuals with higher levels of moral disengagement in meat consumption also tend to show lower levels of general empathy, experience less self-evaluative emotional reactions (i.e. guilt and shame) when considering the impact of meat consumption, endorse group-based discrimination within humans (social dominance orientation), and display power motives of dominance and support of hierarchy of humans over other species (speciesism, human supremacy beliefs). Additionally, they also tend to display higher general propensity to morally disengage, attribute less importance to moral traits in how they view themselves (moral identity), and eat meat more often.

A detailed study of personality characteristics and diet in Americans characterized the self-descriptions of increased meat consumers as "pragmatic" and "business- and action-oriented", after correcting for gender differences.

The idea that "you are what you eat", related to superstitions about sympathetic magic and common in many cultures, may create the perception that eating meat confers animal-like personality attributes.

Masculinity

Two men in identical short-sleeved shirts and camouflage pants, one very dark-skinned with no hat and one very light-skinned wearing a hat and sunglasses, stand smiling over a barbecue full of cooking meat in a bright location.
In Western traditions and stereotypes, meat barbecues have a particularly strong connection with masculinity.
 
In recent years, a considerable amount of social psychology research has investigated the relevance of meat consumption to perceptions of masculinity.

The participants in a series of 2012 studies rated mammalian muscle such as steak and hamburgers as more "male" than other foods, and responded more quickly in an implicit-association test when meat words were paired with typically male names than with female names. In a different study, perceptions of masculinity among a sample of American undergraduates were positively linked to targets' beef consumption and negatively linked to vegetarianism. A 2011 Canadian study found that both omnivores and vegetarians perceived vegetarians as less masculine.

Cultural associations between meat and masculinity are reflected in individuals' attitudes and choices. Across Western societies, women eat significantly less meat than men on average and are more likely to be vegetarian. Women are also more likely than men to avoid meat for ethical reasons. A 2016 review found that male Germans eat more meat than females, linking the discrepancy to the finding that meat in Western culture has symbolic connections to strength and power, which are associated with male gender roles.

Studies have also examined meat eating in the context of attempts to manage others' impressions of the eater, finding that men whose masculinity had been challenged chose to eat more meat pizza instead of vegetable pizza. These results indicate that it is possible for dietary choices to influence perceptions of the eater's masculinity or femininity, with meat strongly correlated with perceived masculinity. It has been suggested that meat consumption makes men feel more masculine, but it remains unclear whether this is the case and how this may be affected by social context.

Morality

In the course of human evolution, the pressures associated with obtaining meat required early hominids to cooperate in hunting, and in distributing the spoils afterwards. In a 2003 paper, psychologist Matteo Marneli proposed that these pressures created the basic principles of human moral judgements: put simply, he argued, "meat made us moral."

Several studies have found that both omnivores and vegetarians tend to consider vegetarians slightly more moral and virtuous than omnivores. Ethical principles are often cited among reasons to stop eating meat. Some evidence suggests meat-eaters may consider vegetarianism an implicit moral reproach, and respond defensively to vegetarian ideas.

A 2015 study found that Belgian omnivores, semi-vegetarians (flexitarians), and vegetarians have fundamentally different moral outlooks on animal welfare concerns. However, the three groups were found to donate equally to human-focused charities.

Other research has shown how moral disengagement operates in the deactivation of moral self-regulatory processes when considering the impact of meat consumption. In particular, a 2016 study offered an interpretation of moral disengagement as a motivated reasoning process which is triggered by loss aversion and dissonance avoidance.

Moral perspectives can have a strong influence on meat consumption, but are not uniform across cultures. In the West, choices about meat eating are known to be associated with moral concerns about animal welfare. In contrast, the psychology of diet in non-Western cultures has been poorly studied, even though important variations exist from region to region; for example, approximately one third of Indians are vegetarian. Research has indicated that, relative to Western vegetarians, Indian vegetarians are more likely to endorse the moral values of purity, legitimate authority, and respect for ingroup and tradition.

Spectrum disorder

From Wikipedia, the free encyclopedia
A spectrum disorder is a mental disorder that includes a range of linked conditions, sometimes also extending to include singular symptoms and traits. The different elements of a spectrum either have a similar appearance or are thought to be caused by the same underlying mechanism. In either case, a spectrum approach is taken because there appears to be "not a unitary disorder but rather a syndrome composed of subgroups". The spectrum may represent a range of severity, comprising relatively "severe" mental disorders through to relatively "mild and nonclinical deficits".

In some cases, a spectrum approach joins together conditions that were previously considered separately. A notable example of this trend is the autism spectrum, where conditions on this spectrum may now all be referred to as autism spectrum disorders. In other cases, what was treated as a single disorder comes to be seen (or seen once again) as comprising a range of types, a notable example being the bipolar spectrum. A spectrum approach may also expand the type or the severity of issues which are included, which may lessen the gap with other diagnoses or with what is considered "normal". Proponents of this approach argue that it is in line with evidence of gradations in the type or severity of symptoms in the general population.

Origin

The visible color spectrum
 
The term spectrum was originally used in physics to indicate an apparent qualitative distinction arising from a quantitative continuum (i.e. a series of distinct colors experienced when a beam of white light is dispersed by a prism according to wavelength). Isaac Newton first used the word spectrum (Latin for "appearance" or "apparition") in print in 1671, in describing his experiments in optics

The term was first used by analogy in psychiatry with a slightly different connotation, to identify a group of conditions that is qualitatively distinct in appearance but believed to be related from an underlying pathogenic point of view. It has been noted that for clinicians trained after the publication of DSM-III (1980), the spectrum concept in psychiatry may be relatively new, but that it has a long and distinguished history that dates back to Emil Kraepelin and beyond. A dimensional concept was proposed by Ernst Kretschmer in 1921 for schizophrenia (schizothymic – schizoid – schizophrenic) and for affective disorders (cyclothymic temperament – cycloid 'psychopathy' – manic-depressive disorder), as well as by Eugen Bleuler in 1922. The term "spectrum" was first used in psychiatry in 1968 in regard to a postulated schizophrenia spectrum, at that time meaning a linking together of what were then called "schizoid personalities", in people diagnosed with schizophrenia and their genetic relatives (see Seymour S. Kety).

For different investigators, the hypothetical common disease-causing link has been of a different nature.

Related concepts

A spectrum approach generally overlays or extends a categorical approach, which today is most associated with the Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Statistical Classification of Diseases and Related Health Problems (ICD). In these diagnostic guides, disorders are considered present if there is a certain combination and number of symptoms. Gradations of present versus absent are not allowed, although there may be subtypes of severity within a category. The categories are also polythetic, because a constellation of symptoms is laid out and different patterns of them can qualify for the same diagnosis. These categories are aids important for us practical purposes such as providing specific labels to facilitate payments for mental health professionals. They have been described as clearly worded, with observable criteria, and therefore an advance over some previous models for research purposes.

A spectrum approach sometimes starts with the nuclear, classic DSM diagnostic criteria for a disorder (or may join together several disorders), and then include an additional broad range of issues such as temperaments or traits, lifestyle, behavioral patterns, and personality characteristics.

In addition, the term 'spectrum' may be used interchangeably with continuum, although the latter goes further in suggesting a direct straight line with no significant discontinuities. Under some continuum models, there are no set types or categories at all, only different dimensions along which everyone varies (hence a dimensional approach).

An example can be found in personality or temperament models. For example, a model that was derived from linguistic expressions of individual differences is subdivided into the Big Five personality traits, where everyone can be assigned a score along each of the five dimensions. This is by contrast to models of 'personality types' or temperament, where some have a certain type and some do not. Similarly, in the classification of mental disorders, a dimensional approach, which is being considered for the DSM-V, would involve everyone having a score on personality trait measures. A categorical approach would only look for the presence or absence of certain clusters of symptoms, perhaps with some cut-off points for severity for some symptoms only, and as a result diagnose some people with personality disorders.

A spectrum approach, by comparison, suggests that although there is a common underlying link, which could be continuous, particular sets of individuals present with particular patterns of symptoms (i.e. syndrome or subtype), reminiscent of the visible spectrum of distinct colors after refraction of light by a prism.

It has been argued that within the data used to develop the DSM system there is a large literature leading to the conclusion that a spectrum classification provides a better perspective on phenomenology (appearance and experience) of psychopathology (mental difficulties) than a categorical classification system. However, the term has a varied history, meaning one thing when referring to a schizophrenia spectrum and another when referring to bipolar or obsessive–compulsive disorder spectrum, for example.

Types of spectrum

The widely used DSM and ICD (Chapter 5) manuals are generally limited to categorical diagnoses. However, some categories include a range of subtypes which vary from the main diagnosis in clinical presentation or typical severity. Some categories could be considered subsyndromal (not meeting criteria for the full diagnosis) subtypes. In addition, many of the categories include a 'not otherwise specified' subtype, where enough symptoms are present but not in the main recognized pattern; in some categories this is the most common diagnosis. 

Spectrum concepts used in research or clinical practice include the following.

Anxiety, stress, and dissociation

Several types of spectrum are in use in these areas, some of which are being considered in the DSM-5.

A generalized anxiety spectrum – this spectrum has been defined by duration of symptoms: a type lasting over six months (a DSM-IV criterion), over one month (DSM-III), or lasting two weeks or less (though may recur), and also isolated anxiety symptoms not meeting criteria for any type.

A social anxiety spectrum – this has been defined to span shyness to social anxiety disorder, including typical and atypical presentations, isolated signs and symptoms, and elements of avoidant personality disorder

A panic-agoraphobia spectrum – due to the heterogeneity (diversity) found in individual clinical presentations of panic disorder and agoraphobia, attempts have been made to identify symptom clusters in addition to those included in the DSM diagnoses, including through the development of a dimensional questionnaire measure. 

A post-traumatic stress spectrum or trauma and loss spectrum – work in this area has sought to go beyond the DSM category and consider in more detail a spectrum of severity of symptoms (rather than just presence or absence for diagnostic purposes), as well as a spectrum in terms of the nature of the stressor (e.g. the traumatic incident) and a spectrum of how people respond to trauma. This identifies a significant amount of symptoms and impairment below threshold for DSM diagnosis but nevertheless important, and potentially also present in other disorders a person might be diagnosed with. 

A depersonalization-derealization spectrum – although the DSM identifies only a chronic and severe form of depersonalization disorder, and the ICD a 'depersonalization-derealization syndrome', a spectrum of severity has long been identified, including short-lasting episodes commonly experienced in the general population and often associated with other disorders.

Obsessions and compulsions

An obsessive–compulsive spectrum – this can include a wide range of disorders from Tourette syndrome to the hypochondrias, as well as forms of eating disorder, itself a spectrum of related conditions.

General developmental disorders

An autistic spectrum – in its simplest form this joins together autism and Asperger syndrome, and can additionally include other pervasive developmental disorders (PDD). These include PDD 'not otherwise specified' (including 'atypical autism'), as well as Rett syndrome and childhood disintegrative disorder (CDD). The first three of these disorders are commonly called the autism spectrum disorders; the last two disorders are much rarer, and are sometimes placed in the autism spectrum and sometimes not. The merging of these disorders is based on findings that the symptom profiles are similar, such that individuals are better differentiated by clinical specifiers (i.e. dimensions of severity, such as extent of social communication difficulties or how fixed or restricted behaviors or interests are) and associated features (e.g. known genetic disorders, epilepsy, intellectual disabilities). The term specific developmental disorders is reserved for categorizing particular specific learning disabilities and developmental disorders affecting coordination.

Psychosis

The schizophrenia spectrum or psychotic spectrum – there are numerous psychotic spectrum disorders already in the DSM, many involving reality distortion. These include:
There are also traits identified in first degree relatives of those diagnosed with schizophrenia associated with the spectrum. Other spectrum approaches include more specific individual phenomena which may also occur in non-clinical forms in the general population, such as some paranoid beliefs or hearing voices. Some researchers have also proposed that avoidant personality disorder and related social anxiety traits should be considered part of a schizophrenia spectrum. Psychosis accompanied by mood disorder may be included as a schizophrenia spectrum disorder, or may be classed separately as below.

Schizoaffective disorders

A schizoaffective spectrum – this spectrum refers to features of both psychosis (hallucinations, delusions, thought disorder etc.) and mood disorder (see below). The DSM has, on the one hand, a category of schizoaffective disorder (which may be more affective (mood) or more schizophrenic), and on the other hand psychotic bipolar disorder and psychotic depression categories. A spectrum approach joins these together, and may additionally include specific clinical variables and outcomes, which initial research suggested may not be particularly well captured by the different diagnostic categories except at the extremes.

Schizophrenia-like PDs

Schizoid personality disorder, schizotypal personality disorder, and paranoid personality disorder can be considered Schizophrenia-like Personality Disorders because of their links to the schizophrenia spectrum.

Mood

A mood disorder (affective) spectrum or bipolar spectrum or depressive spectrum. These approaches have expanded out in different directions. On the one hand, work on major depressive disorder has identified a spectrum of subcategories and subthreshold symptoms which are prevalent, recurrent and associated with treatment needs. People are found to move between the subtypes and the main diagnostic type over time, suggesting a spectrum. This spectrum can include already recognised categories of minor depressive disorder, 'melancholic depression' and various kinds of atypical depression

Going in another direction, numerous links and overlaps have been found between major depressive disorder and bipolar syndromes, including mixed states (simultaneous depression and mania or hypomania). Hypomanic ('below manic') and more rarely manic signs and symptoms have been found in a significant number of cases of major depressive disorder, suggesting not a categorical distinction but a dimension of frequency which is higher in bipolar II and higher again in bipolar I. In addition, numerous subtypes of bipolar have been proposed beyond the types already in the DSM (which includes a milder form called cyclothymia). These extra subgroups have been defined in terms of more detailed gradations of mood severity, or the rapidity of cycling, or the extent or nature of psychotic symptoms. Furthermore, due to shared characteristics between some types of bipolar disorder and borderline personality disorder, some researchers have suggested they may both lie on a spectrum of affective disorders, although others see more links to post-trauma syndromes.

Substance use

A spectrum of drug use, drug abuse and substance dependence – one spectrum of this type, adopted by the Health Officers Council of British Columbia in 2005, does not employ loaded terms and distinctions such as "use" vs. "abuse", but explicitly recognizes a spectrum ranging from potentially beneficial to chronic dependence (also known as addiction). The model includes the role not just of the individual but of society, culture and availability of substances. In concert with the identified spectrum of drug use, a spectrum of policy approaches was identified which depended partly on whether the drug in question was available in a legal, for-profit commercial economy, or at the other of the spectrum only in a criminal/prohibition, black-market economy. In addition, a standardized questionnaire has been developed in psychiatry based on a spectrum concept of substance use.

Paraphilias and obsessions

The interpretative key of "Spectrum", developed from the concept of Related Disorders has been considered also in paraphilias.

Paraphilic behavior is triggered by thoughts or urges that are psychopathologically close to obsessive impulsive area. Hollander (1996) includes in the obsessive-compulsive spectrum neurological related obsessive disorders, body perception related disorders and impulsivity-compulsivity disorders. In this continuum from impulsivity to compulsivity is particularly hard to find a clear borderline between the two entities.

On this point of view, paraphilias represent such as sexual behaviors due to a high impulsivity-compulsivity drive. It is difficult to distinguish impulsivity from compulsivity: sometimes paraphilic behaviors are prone to achieve pleasure (desire or fantasy), in some other cases these attitudes are merely expressions of anxiety, and the behavioral perversion is an attempt to reduce anxiety. In the last case, the pleasure gained is short in time and is followed by a new increase in anxiety levels, such as it can be seen in an obsessive patient after he performs his compulsion.

Eibl-Eibelsfeldt (1984) underlines a female sexual arousal condition during flight and fear reactions. Some women, with masochistic traits, can reach orgasm in such conditions.

Broad spectrum approach

Various higher-level types of spectrum have also been proposed, that subsume conditions into fewer but broader overarching groups.

One psychological model based on factor analysis, originating from developmental studies but also applied to adults, posits that many disorders fall on either an "internalizing" spectrum (characterized by negative affectivity; subdivides into a "distress" subspectrum and a "fear" subspectrum) or an "externalizing" spectrum (characterized by negativity affectivity plus disinhibition). These spectra are hypothetically linked to underlying variation in some of the Big five personality traits. Another theoretical model proposes that the dimensions of fear and anger, defined in a broad sense, underlie a broad spectrum of mood, behavioral and personality disorders. In this model, different combinations of excessive or deficient fear and anger correspond to different neuropsychological temperament types hypothesized to underlie the spectrum of disorders.

Similar approaches refer to the overall 'architecture' or 'meta-structure', particularly in relation to the development of the DSM or ICD systems. Five proposed meta-structure groupings were recently proposed in this way, based on views and evidence relating to risk factors and clinical presention. The clusters of disorder that emerged were described as neurocognitive (identified mainly by neural substrate abnormalities), neurodevelopmental (identified mainly by early and continuing cognitive deficits), psychosis (identified mainly by clinical features and biomarkers for information processing deficits), emotional (identified mainly by being preceded by a temperament of negative emotionality), and externalizing (identified mainly be being preceded by disinhibition). However, the analysis was not necessarily able to validate one arrangement over others. From a psychological point of view, it has been suggested that the underlying phenomena are too complex, inter-related and continuous – with too poorly understood a biological or environmental basis – to expect that everything can be mapped into a set of categories for all purposes. In this context the overall system of classification is to some extent arbitrary, and could be thought of as a user inferface which may need to satisfy different purposes.

Galaxy formation and evolution

From Wikipedia, the free encyclopedia
 
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, that clustering and merging allows galaxies to accumulate mass, determining both their shape and structure.

Commonly observed properties of galaxies

Hubble tuning fork diagram of galaxy morphology
 
Because of the inability to conduct experiments in outer space, the only way to “test” theories and models of galaxy evolution is to compare them with observations. Explanations for how galaxies formed and evolved must be able to predict the observed properties and types of galaxies.

Edwin Hubble created the first galaxy classification scheme known as the Hubble tuning-fork diagram. It partitioned galaxies into ellipticals, normal spirals, barred spirals (such as the Milky Way), and irregulars. These galaxy types exhibit the following properties which can be explained by current galaxy evolution theories:
  • Many of the properties of galaxies (including the galaxy color–magnitude diagram) indicate that there are fundamentally two types of galaxies. These groups divide into blue star-forming galaxies that are more like spiral types, and red non-star forming galaxies that are more like elliptical galaxies.
  • Spiral galaxies are quite thin, dense, and rotate relatively fast, while the stars in elliptical galaxies have randomly-oriented orbits.
  • The majority of giant galaxies contain a supermassive black hole in their centers, ranging in mass from millions to billions of times the mass of our Sun. The black hole mass is tied to the host galaxy bulge or spheroid mass.
  • Metallicity has a positive correlation with the absolute magnitude (luminosity) of a galaxy.
There is a common misconception that Hubble believed incorrectly that the tuning fork diagram described an evolutionary sequence for galaxies, from elliptical galaxies through lenticulars to spiral galaxies. This is not the case; instead, the tuning fork diagram shows an evolution from simple to complex with no temporal connotations intended. Astronomers now believe that disk galaxies likely formed first, then evolved into elliptical galaxies through galaxy mergers. 

Current models also predict that the majority of mass in galaxies is made up of dark matter, a substance which is not directly observable, and might not interact through any means except gravity. This observation arises because galaxies could not have formed as they have, or rotate as they are seen to, unless they contain far more mass than can be directly observed.

Formation of disk galaxies

The earliest stage in the evolution of galaxies is the formation. When a galaxy forms, it has a disk shape and is called a spiral galaxy due to spiral-like "arm" structures located on the disk. There are different theories on how these disk-like distributions of stars develop from a cloud of matter: however, at present, none of them exactly predicts the results of observation.

Top-down theories

Olin Eggen, Donald Lynden-Bell, and Allan Sandage in 1962, proposed a theory that disk galaxies form through a monolithic collapse of a large gas cloud. The distribution of matter in the early universe was in clumps that consisted mostly of dark matter. These clumps interacted gravitationally, putting tidal torques on each other that acted to give them some angular momentum. As the baryonic matter cooled, it dissipated some energy and contracted toward the center. With angular momentum conserved, the matter near the center speeds up its rotation. Then, like a spinning ball of pizza dough, the matter forms into a tight disk. Once the disk cools, the gas is not gravitationally stable, so it cannot remain a singular homogeneous cloud. It breaks, and these smaller clouds of gas form stars. Since the dark matter does not dissipate as it only interacts gravitationally, it remains distributed outside the disk in what is known as the dark halo. Observations show that there are stars located outside the disk, which does not quite fit the "pizza dough" model. It was first proposed by Leonard Searle and Robert Zinn  that galaxies form by the coalescence of smaller progenitors. Known as a top-down formation scenario, this theory is quite simple yet no longer widely accepted.

Bottom-up theories

More recent theories include the clustering of dark matter halos in the bottom-up process. Instead of large gas clouds collapsing to form a galaxy in which the gas breaks up into smaller clouds, it is proposed that matter started out in these “smaller” clumps (mass on the order of globular clusters), and then many of these clumps merged to form galaxies, which then were drawn by gravitation to form galaxy clusters. This still results in disk-like distributions of baryonic matter with dark matter forming the halo for all the same reasons as in the top-down theory. Models using this sort of process predict more small galaxies than large ones, which matches observations. 

Astronomers do not currently know what process stops the contraction. In fact, theories of disk galaxy formation are not successful at producing the rotation speed and size of disk galaxies. It has been suggested that the radiation from bright newly formed stars, or from an active galactic nucleus can slow the contraction of a forming disk. It has also been suggested that the dark matter halo can pull the galaxy, thus stopping disk contraction.

The Lambda-CDM model is a cosmological model that explains the formation of the universe after the Big Bang. It is a relatively simple model that predicts many properties observed in the universe, including the relative frequency of different galaxy types; however, it underestimates the number of thin disk galaxies in the universe. The reason is that these galaxy formation models predict a large number of mergers. If disk galaxies merge with another galaxy of comparable mass (at least 15 percent of its mass) the merger will likely destroy, or at a minimum greatly disrupt the disk, and the resulting galaxy is not expected to be a disk galaxy (see next section). While this remains an unsolved problem for astronomers, it does not necessarily mean that the Lambda-CDM model is completely wrong, but rather that it requires further refinement to accurately reproduce the population of galaxies in the universe.

Galaxy mergers and the formation of elliptical galaxies

Artist image of a firestorm of star birth deep inside core of young, growing elliptical galaxy.
 
NGC 4676 (Mice Galaxies) is an example of a present merger.
 
Antennae Galaxies are a pair of colliding galaxies – the bright, blue knots are young stars that have recently ignited as a result of the merger.
 
ESO 325-G004, a typical elliptical galaxy.

Elliptical galaxies (such as IC 1101) are among some of the largest known thus far. Their stars are on orbits that are randomly oriented within the galaxy (i.e. they are not rotating like disk galaxies). A distinguishing feature of elliptical galaxies is that the velocity of the stars does not necessarily contribute to flattening of the galaxy, such as in spiral galaxies. Elliptical galaxies have central supermassive black holes, and the masses of these black holes correlate with the galaxy's mass.

Elliptical galaxies have two main stages of evolution. The first is due to the supermassive black hole growing by accreting cooling gas. The second stage is marked by the black hole stabilizing by suppressing gas cooling, thus leaving the elliptical galaxy in a stable state. The mass of the black hole is also correlated to a property called sigma which is the dispersion of the velocities of stars in their orbits. This relationship, known as the M-sigma relation, was discovered in 2000. Elliptical galaxies mostly lack disks, although some bulges of disk galaxies resemble elliptical galaxies. Elliptical galaxies are more likely found in crowded regions of the universe (such as galaxy clusters). 

Astronomers now see elliptical galaxies as some of the most evolved systems in the universe. It is widely accepted that the main driving force for the evolution of elliptical galaxies is mergers of smaller galaxies. Many galaxies in the universe are gravitationally bound to other galaxies, which means that they will never escape their mutual pull. If the galaxies are of similar size, the resultant galaxy will appear similar to neither of the progenitors, but will instead be elliptical. There are many types of galaxy mergers, which do not necessarily result in elliptical galaxies, but result in a structural change. For example, a minor merger event is thought to be occurring between the Milky Way and the Magellanic Clouds. 

Mergers between such large galaxies are regarded as violent, and the frictional interaction of the gas between the two galaxies can cause gravitational shock waves, which are capable of forming new stars in the new elliptical galaxy. By sequencing several images of different galactic collisions, one can observe the timeline of two spiral galaxies merging into a single elliptical galaxy.

In the Local Group, the Milky Way and the Andromeda Galaxy are gravitationally bound, and currently approaching each other at high speed. Simulations show that the Milky Way and Andromeda are on a collision course, and are expected to collide in less than five billion years. During this collision, it is expected that the Sun and the rest of the Solar System will be ejected from its current path around the Milky Way. The remnant could be a giant elliptical galaxy.

Galaxy quenching

Star formation in what are now "dead" galaxies sputtered out billions of years ago.
 
One observation (see above) that must be explained by a successful theory of galaxy evolution is the existence of two different populations of galaxies on the galaxy color-magnitude diagram. Most galaxies tend to fall into two separate locations on this diagram: a "red sequence" and a "blue cloud". Red sequence galaxies are generally non-star-forming elliptical galaxies with little gas and dust, while blue cloud galaxies tend to be dusty star-forming spiral galaxies.

As described in previous sections, galaxies tend to evolve from spiral to elliptical structure via mergers. However, the current rate of galaxy mergers does not explain how all galaxies move from the "blue cloud" to the "red sequence". It also does not explain how star formation ceases in galaxies. Theories of galaxy evolution must therefore be able to explain how star formation turns off in galaxies. This phenomenon is called galaxy "quenching".

Stars form out of cold gas, so a galaxy is quenched when it has no more cold gas. However, it is thought that quenching occurs relatively quickly (within 1 billion years), which is much shorter than the time it would take for a galaxy to simply use up its reservoir of cold gas. Galaxy evolution models explain this by hypothesizing other physical mechanisms that remove or shut off the supply of cold gas in a galaxy. These mechanisms can be broadly classified into two categories: (1) preventive feedback mechanisms that stop cold gas from entering a galaxy or stop it from producing stars, and (2) ejective feedback mechanisms that remove gas so that it cannot form stars.

One theorized preventive mechanism called “strangulation” keeps cold gas from entering the galaxy. Strangulation is likely the main mechanism for quenching star formation in nearby low-mass galaxies. The exact physical explanation for strangulation is still unknown, but it may have to do with a galaxy's interactions with other galaxies. As a galaxy falls into a galaxy cluster, gravitational interactions with other galaxies can strangle it by preventing it from accreting more gas. For galaxies with massive dark matter halos, another preventive mechanism called “virial shock heating” may also prevent gas from becoming cool enough to form stars.

Ejective processes, which expel cold gas from galaxies, may explain how more massive galaxies are quenched. One ejective mechanism is caused by supermassive black holes found in the centers of galaxies. Simulations have shown that gas accreting onto supermassive black holes in galactic centers produces high-energy jets; the released energy can expel enough cold gas to quench star formation.

Our own Milky Way and the nearby Andromeda Galaxy currently appear to be undergoing the quenching transition from star-forming blue galaxies to passive red galaxies.

Autism spectrum

From Wikipedia, the free encyclopedia
 
Autism spectrum
Other namesAutism spectrum disorder (ASD), autism spectrum condition (ASC)
Boy stacking cans
Repetitively stacking or lining up objects is associated with autism.
SpecialtyPsychiatry
SymptomsProblems with communication, social interaction, restricted interests, repetitive behavior
ComplicationsSocial isolation, employment problems, family stress, bullying
Usual onsetBy the age of 3 years
Risk factorsAdvanced parental age, exposure to valproate during pregnancy, low birth weight
Diagnostic methodBased on symptoms
Differential diagnosisIntellectual disability, Rett syndrome, ADHD, selective mutism, childhood-onset schizophrenia
TreatmentBehavioral therapy, psychotropic medication
Frequency1% of people (62.2 million 2015)

Autism spectrum, also known as autism spectrum disorder (ASD), is a range of mental disorders of the neurodevelopmental type. It includes autism and Asperger syndrome. Individuals on the spectrum often experience difficulties with social communication and interaction; and restricted, repetitive patterns of behavior, interests or activities. Symptoms are typically recognized between one and two years of age. Long-term problems may include difficulties in performing daily tasks, creating and keeping relationships, and maintaining a job.

The cause of autism spectrum is uncertain. Risk factors include having an older parent, a family history of autism, and certain genetic conditions. It is estimated that between 64% and 91% of risk is due to family history. Diagnosis is based on symptoms. The DSM-5 redefined the autism spectrum disorders to encompass the previous diagnoses of autism, Asperger syndrome, pervasive developmental disorder not otherwise specified (PDD-NOS), and childhood disintegrative disorder.

Treatment efforts are generally individualized, and can include behavioural therapy, and the teaching of coping skills. Medications may be used to try to help improve symptoms. Evidence to support the use of medications, however, is not very strong.

Autism spectrum is estimated to affect about 1% of people (62.2 million globally as of 2015). Males are diagnosed more often than females. The term "spectrum" can refer to the range of symptoms or their severity, leading some to favor a distinction between severely disabled autistics who cannot speak or look after themselves, and higher functioning autistics.

Classification

In the United States, a revision to autism spectrum disorder (ASD) was presented in the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM-5), released May 2013. The new diagnosis encompasses previous diagnoses of autistic disorder, Asperger syndrome, childhood disintegrative disorder, and PDD-NOS. Compared with the DSM-IV diagnosis of autistic disorder, the DSM-5 diagnosis of ASD no longer includes communication as a separate criterion, and has merged social interaction and communication into one category. Slightly different diagnostic definitions are used in other countries. For example, the ICD-10 is the most commonly-used diagnostic manual in the UK and European Union. Rather than categorizing these diagnoses, the DSM-5 has adopted a dimensional approach to diagnosing disorders that fall underneath the autism spectrum umbrella. Some have proposed that individuals on the autism spectrum may be better represented as a single diagnostic category. Within this category, the DSM-5 has proposed a framework of differentiating each individual by dimensions of severity, as well as associated features (i.e., known genetic disorders, and intellectual disability).

Another change to the DSM includes collapsing social and communication deficits into one domain. Thus, an individual with an ASD diagnosis will be described in terms of severity of social communication symptoms, severity of fixated or restricted behaviors or interests, hyper- or hyposensitivity to sensory stimuli, and associated features. The restricting of onset age has also been loosened from 3 years of age to "early developmental period", with a note that symptoms may manifest later when social demands exceed capabilities.

Autism forms the core of the autism spectrum disorders. Asperger syndrome is closest to autism in signs and likely causes; unlike autism, people with Asperger syndrome usually have no significant delay in language development, according to the older DSM-IV criteria. PDD-NOS is diagnosed when the criteria are not met for a more specific disorder. Some sources also include Rett syndrome and childhood disintegrative disorder, which share several signs with autism but may have unrelated causes; other sources differentiate them from ASD, but group all of the above conditions into the pervasive developmental disorders.

Autism, Asperger syndrome, and PDD-NOS are sometimes called the autistic disorders instead of ASD, whereas autism itself is often called autistic disorder, childhood autism, or infantile autism. Although the older term pervasive developmental disorder and the newer term autism spectrum disorder largely or entirely overlap, the earlier was intended to describe a specific set of diagnostic labels, whereas the latter refers to a postulated spectrum disorder linking various conditions. ASD is a subset of the broader autism phenotype (BAP), which describes individuals who may not have ASD but do have autistic-like traits, such as avoiding eye contact.

Signs and symptoms

Autism is characterized by persistent deficits in social communication and interaction across multiple contexts, as well as restricted, repetitive patterns of behavior, interests, or activities. These deficits are present in early childhood, and lead to clinically significant functional impairment. There is also a unique form of autism called autistic savantism, where a child can display outstanding skills in music, art, and numbers with no practice. Because of its relevance to different populations, self-injurious behaviors (SIB) are not considered a core characteristic of the ASD population however approximately 50% of those with ASD take part in some type of SIB (head-banging, self-biting) and are more at risk than other groups with developmental disabilities.

Other characteristics of ASD include restricted and repetitive behaviors (RRBs) which include a large range of specific gestures and acts, it can even include certain behavioral traits as defined in the Diagnostic and Statistic Manual for Mental Disorders.

Asperger syndrome was distinguished from autism in the DSM-IV by the lack of delay or deviance in early language development. Additionally, individuals diagnosed with Asperger syndrome did not have significant cognitive delays. PDD-NOS was considered "subthreshold autism" and "atypical autism" because it was often characterized by milder symptoms of autism or symptoms in only one domain (such as social difficulties). The DSM-5 eliminated the four separate diagnoses: Asperger Syndrome, Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS), Childhood Disintegrative Disorder, and Autistic Disorder and combined them under the diagnosis of Autism Spectrum Disorder.

Behavioral characteristics

Autism spectrum disorders include a wide variety of characteristics. Some of these include behavioral characteristics which widely range from slow development of social and learning skills to difficulties creating connections with other people. They may develop these difficulties of creating connections due to anxiety or depression, which people with autism are more likely to experience, and as a result isolate themselves. Other behavioral characteristics include abnormal responses to sensations including sights, sounds, touch, and smell, and problems keeping a consistent speech rhythm. The latter problem influences an individual's social skills, leading to potential problems in how they are understood by communication partners. Behavioral characteristics displayed by those with autism spectrum disorder typically influence development, language, and social competence. Behavioral characteristics of those with autism spectrum disorder can be observed as perceptual disturbances, disturbances of development rate, relating, speech and language, and motility.

Developmental course

Autism spectrum disorders are thought to follow two possible developmental courses, although most parents report that symptom onset occurred within the first year of life. One course of development is more gradual in nature, in which parents report concerns in development over the first two years of life and diagnosis is made around 3–4 years of age. Some of the early signs of ASDs in this course include decreased looking at faces, failure to turn when name is called, failure to show interests by showing or pointing, and delayed imaginative play.

A second course of development is characterized by normal or near-normal development followed by loss of skills or regression in the first 2–3 years. Regression may occur in a variety of domains, including communication, social, cognitive, and self-help skills; however, the most common regression is loss of language.

There continues to be a debate over the differential outcomes based on these two developmental courses. Some studies suggest that regression is associated with poorer outcomes and others report no differences between those with early gradual onset and those who experience a regression period. While there is conflicting evidence surrounding language outcomes in ASD, some studies have shown that cognitive and language abilities at age ​2 12 may help predict language proficiency and production after age 5. Overall, the literature stresses the importance of early intervention in achieving positive longitudinal outcomes.

Social skills

Social skills present the most challenges for individuals with ASD. This leads to problems with friendships, romantic relationships, daily living, and vocational success. Marriages are less common for those with ASD. Many of these challenges are linked to their atypical patterns of behavior and communication. It is common for children and adults with autism to struggle with social interactions because they are unable to relate to their peers. All of these issues stem from cognitive impairments. Difficulty in this thought process is called "theory of the mind" or mind blindness which means that the mind has difficulty with thought process as well as being aware of what is going on around them. Theory of mind is closely related to the pragmatic difficulties children with autism experience.

Communication skills

Communication deficits are generally characterized by impairments regarding joint attention and social reciprocity, challenges with verbal language cues, and poor nonverbal communication skills  such as lack of eye contact and meaningful gestures and facial expressions. Language behaviors typically seen in children with autism may include repetitive or rigid language, specific interests in conversation, and atypical language development. ASD is a complex pragmatic language disorder which influences communication skills significantly. Many children with ASD develop language skills at an uneven pace where they easily acquire some aspects of communication, while never fully developing other aspects. In some cases, individuals remain completely nonverbal throughout their lives, although the accompanying levels of literacy and nonverbal communication skills vary.

They may not pick up on body language or social cues such as eye contact and facial expressions if they provide more information than the person can process at that time. Similarly, they have trouble recognizing subtle expressions of emotion and identifying what various emotions mean for the conversation. They struggle with understanding the context and subtext of conversational or printed situations, and have trouble forming resulting conclusions about the content. This also results in a lack of social awareness and atypical language expression.

It is also common for individuals with ASD to communicate strong interest in a specific topic, speaking in lesson-like monologues about their passion instead of enabling reciprocal communication with whomever they are speaking to. What looks like self-involvement or indifference toward others stems from a struggle to recognize or remember that other people have their own personalities, perspectives, and interests. The ability to be focused in on one topic in communication is known as monotropism, and can be compared to "tunnel vision" in the mind for those individuals with ASD. Language expression by those on the autism spectrum is often characterized by repetitive and rigid language. Often children with ASD repeat certain words, numbers, or phrases during an interaction, words unrelated to the topic of conversation. They can also exhibit a condition called echolalia in which they respond to a question by repeating the inquiry instead of answering. However, this repetition can be a form of meaningful communication, a way that individuals with ASD try to express a lack of understanding or knowledge regarding the answer to the question.

Causes

While specific causes of autism spectrum disorders have yet to be found, many risk factors identified in the research literature may contribute to their development. These risk factors include genetics, prenatal and perinatal factors, neuroanatomical abnormalities, and environmental factors. It is possible to identify general risk factors, but much more difficult to pinpoint specific factors. Given the current state of knowledge, prediction can only be of a global nature and therefore requires the use of general markers.

Genetic risk factors

As of 2018, understanding of genetic risk factors had shifted from a focus on a few alleles, to an understanding that genetic involvement in ASD is probably diffuse, depending on a large number of variants, some of which are common and have a small effect, and some of which are rare and have a large effect. The most common gene disrupted with large effect rare variants appeared to be CHD8, but less than 0.5% of people with ASD have such a mutation. Some ASD is associated with clearly genetic conditions, like fragile X syndrome; however only around 2% of people with ASD have fragile X.

As of 2018, it appeared that somewhere between 74% and 93% of ASD risk is heritable and that after an older child is diagnosed with ASD, 7–20% of subsequent children are likely to be as well. If parents have a child with ASD they have a 2% to 8% chance of having a second child with ASD. If the child with ASD is an identical twin the other will be affected 36 to 95 percent of the time. If they are fraternal twins the other will only be affected up to 31 percent of the time.

Some of the alterations that contribute to the development of the autistic spectrum: SNVs (single-nucleotide variations), indels (insertions-deletions) and SVs (structural variants). These associations have been identified through whole-genome studies, such as WGS (whole-genome sequencing) and GWAS (genome-wide analysis association studies). 

In early onset disorders, such as autism, de novo mutations have been identified as risk factors. One study has identified 64 SNVs and 5 indels de novo on average. By performing an analysis of these variants, comparing cases and controls, considering SNVs and indels in 179 genes associated with autism or close to them, studies observed that the relative risk of missense mutations or variants in promoter regions and UTR (untranslated region), increases versus controls. 

The identification of SVs has been very useful too, since structural alterations in the chromosomes are able to rearrange the genome, altering its functionality, depending on the size and the region they affect. 

After the analysis, 98,785 SVs were identified, with an average of 5,843 variants per individual: 171 SVs were de novo, more frequent in the germ line. Some of these variants affected genes associated with autism, such as the GRIN2B gene, balanced translocation, or the deletion of exons 8, 9, and 10 of the CHD2 gene. 

No significant differences were observed regarding the size of certain rearrangements in cases and controls, though a slight increase in number was observed for cases relative to controls.

All these genetic variants contribute to the development of the autistic spectrum, however, it can not be guaranteed that they are determinants for the development.

Prenatal and perinatal risk factors

Several prenatal and perinatal complications have been reported as possible risk factors for autism. These risk factors include maternal gestational diabetes, maternal and paternal age over 30, bleeding after first trimester, use of prescription medication (e.g. valproate) during pregnancy, and meconium in the amniotic fluid. While research is not conclusive on the relation of these factors to autism, each of these factors has been identified more frequently in children with autism, compared to their siblings who do not have autism, and other typically developing youth. While it is unclear if any single factors during the prenatal phase affect the risk of autism, complications during pregnancy may be a risk.

Low vitamin D levels in early development has been hypothesized as a risk factor for autism.

Disproven vaccine hypothesis

In 1998 Andrew Wakefield led a fraudulent study that suggested that the MMR vaccine may cause autism. This conjecture suggested that autism results from brain damage caused either by the MMR vaccine itself, or by thimerosal, a vaccine preservative. No convincing scientific evidence supports these claims, and further evidence continues to refute them, including the observation that the rate of autism continues to climb despite elimination of thimerosal from routine childhood vaccines. A 2014 meta-analysis examined ten major studies on autism and vaccines involving 1.25 million children worldwide; it concluded that neither the MMR vaccine, which has never contained thimerosal, nor the vaccine components thimerosal or mercury, lead to the development of ASDs.

Pathophysiology

In general, neuroanatomical studies support the concept that autism may involve a combination of brain enlargement in some areas and reduction in others. These studies suggest that autism may be caused by abnormal neuronal growth and pruning during the early stages of prenatal and postnatal brain development, leaving some areas of the brain with too many neurons and other areas with too few neurons. Some research has reported an overall brain enlargement in autism, while others suggest abnormalities in several areas of the brain, including the frontal lobe, the mirror neuron system, the limbic system, the temporal lobe, and the corpus callosum.

In functional neuroimaging studies, when performing theory of mind and facial emotion response tasks, the median person on the autism spectrum exhibits less activation in the primary and secondary somatosensory cortices of the brain than the median member of a properly sampled control population. This finding coincides with reports demonstrating abnormal patterns of cortical thickness and grey matter volume in those regions of autistic persons' brains.

Mirror neuron system

The mirror neuron system (MNS) consists of a network of brain areas that have been associated with empathy processes in humans. In humans, the MNS has been identified in the inferior frontal gyrus (IFG) and the inferior parietal lobule (IPL) and is thought to be activated during imitation or observation of behaviors. The connection between mirror neuron dysfunction and autism is tentative, and it remains to be seen how mirror neurons may be related to many of the important characteristics of autism.

"Social brain" interconnectivity

A number of discrete brain regions and networks among regions that are involved in dealing with other people have been discussed together under the rubric of the "social brain". As of 2012, there was a consensus that autism spectrum is likely related to problems with interconnectivity among these regions and networks, rather than problems with any specific region or network.

Temporal lobe

Functions of the temporal lobe are related to many of the deficits observed in individuals with ASDs, such as receptive language, social cognition, joint attention, action observation, and empathy. The temporal lobe also contains the superior temporal sulcus (STS) and the fusiform face area (FFA), which may mediate facial processing. It has been argued that dysfunction in the STS underlies the social deficits that characterize autism. Compared to typically developing individuals, one fMRI study found that individuals with high-functioning autism had reduced activity in the FFA when viewing pictures of faces.

Mitochondrial dysfunction

It has been suggested that ASD could be linked to mitochondrial disease (MD), a basic cellular abnormality with the potential to cause disturbances in a wide range of body systems. A recent meta-analysis study, as well as other population studies have shown that approximately 5% of children with ASD meet the criteria for classical MD. It is unclear why the MD occurs considering that only 23% of children with both ASD and MD present with mitochondrial DNA (mtDNA) abnormalities.

Serotonin

It has been hypothesized that increased activity of serotonin in the developing brain may facilitate the onset of autism spectrum disorder, with an association found in six out of eight studies between the use of selective serotonin reuptake inhibitors (SSRIs) by the pregnant mother and the development of ASD by the child exposed to SSRI in the antenatal environment. The study could not definitively conclude SSRIs caused the increased risk for ASDs due to the biases found in those studies, and the authors called for more definitive, better conducted studies.

Diagnosis

Evidence-based assessment

ASD can be detected as early as 18 months or even younger in some cases. A reliable diagnosis can usually be made by the age of two years. The diverse expressions of ASD symptoms pose diagnostic challenges to clinicians. Individuals with an ASD may present at various times of development (e.g., toddler, child, or adolescent), and symptom expression may vary over the course of development. Furthermore, clinicians must differentiate among pervasive developmental disorders, and may also consider similar conditions, including intellectual disability not associated with a pervasive developmental disorder, specific language disorders, ADHD, anxiety, and psychotic disorders.

Considering the unique challenges in diagnosing ASD, specific practice parameters for its assessment have been published by the American Academy of Neurology, the American Academy of Child and Adolescent Psychiatry, and a consensus panel with representation from various professional societies. The practice parameters outlined by these societies include an initial screening of children by general practitioners (i.e., "Level 1 screening") and for children who fail the initial screening, a comprehensive diagnostic assessment by experienced clinicians (i.e. "Level 2 evaluation"). Furthermore, it has been suggested that assessments of children with suspected ASD be evaluated within a developmental framework, include multiple informants (e.g., parents and teachers) from diverse contexts (e.g., home and school), and employ a multidisciplinary team of professionals (e.g., clinical psychologists, neuropsychologists, and psychiatrists).

After a child shows initial evidence of ASD tendencies, psychologists administer various psychological assessment tools to assess for ASD. Among these measurements, the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) are considered the "gold standards" for assessing autistic children. The ADI-R is a semi-structured parent interview that probes for symptoms of autism by evaluating a child's current behavior and developmental history. The ADOS is a semistructured interactive evaluation of ASD symptoms that is used to measure social and communication abilities by eliciting several opportunities (or "presses") for spontaneous behaviors (e.g., eye contact) in standardized context. Various other questionnaires (e.g., The Childhood Autism Rating Scale, Autism Treatment Evaluation Checklist) and tests of cognitive functioning (e.g., The Peabody Picture Vocabulary Test) are typically included in an ASD assessment battery.

In the UK, there is some diagnostic use of the Diagnostic Interview for Social and Communication Disorders (DISCO) which was developed for use at The Centre for Social and Communication Disorders, by Lorna Wing and Judith Gould, as both a clinical and a research instrument for use with children and adults of any age. The DISCO is designed to elicit a picture of the whole person through the story of their development and behavior. In clinical work, the primary purpose is to facilitate understanding of the pattern over time of the specific skills and impairments that underlie the overt behavior. If no information is available, the clinician has to obtain as much information as possible concerning the details of current skills and pattern of behavior of the person. This type of dimensional approach to clinical description is useful for prescribing treatment.

Comorbidity

Autism spectrum disorders tend to be highly comorbid with other disorders. Comorbidity may increase with age and may worsen the course of youth with ASDs and make intervention/treatment more difficult. Distinguishing between ASDs and other diagnoses can be challenging, because the traits of ASDs often overlap with symptoms of other disorders, and the characteristics of ASDs make traditional diagnostic procedures difficult.

The most common medical condition occurring in individuals with autism spectrum disorders is seizure disorder or epilepsy, which occurs in 11-39% of individuals with ASD. Tuberous sclerosis, a medical condition in which non-malignant tumors grow in the brain and on other vital organs, occurs in 1-4% of individuals with ASDs.

Intellectual disabilities are some of the most common comorbid disorders with ASDs. Recent estimates suggest that 40-69% of individuals with ASD have some degree of an intellectual disability, more likely to be severe for females. A number of genetic syndromes causing intellectual disability may also be comorbid with ASD, including fragile X syndrome, Down syndrome, Prader-Willi and Angelman syndromes, and Williams syndrome.

Learning disabilities are also highly comorbid in individuals with an ASD. Approximately 25-75% of individuals with an ASD also have some degree of a learning disability.

Various anxiety disorders tend to co-occur with autism spectrum disorders, with overall comorbidity rates of 7-84%. Rates of comorbid depression in individuals with an ASD range from 4-58%. The relationship between ASD and schizophrenia remains a controversial subject under continued investigation, and recent meta-analyses have examined genetic, environmental, infectious, and immune risk factors that may be shared between the two conditions.

Deficits in ASD are often linked to behavior problems, such as difficulties following directions, being cooperative, and doing things on other people's terms. Symptoms similar to those of attention deficit hyperactivity disorder (ADHD) can be part of an ASD diagnosis.

Sensory processing disorder is also comorbid with ASD, with comorbidity rates of 42-88%.

Treatment

There is no known cure for autism, although those with Asperger syndrome and those who have autism and require little-to-no support are more likely to experience a lessening of symptoms over time. The main goals of treatment are to lessen associated deficits and family distress, and to increase quality of life and functional independence. In general, higher IQs are correlated with greater responsiveness to treatment and improved treatment outcomes. Although evidence-based interventions for autistic children vary in their methods, many adopt a psychoeducational approach to enhancing cognitive, communication, and social skills while minimizing problem behaviors. It has been argued that no single treatment is best and treatment is typically tailored to the child's needs.

Intensive, sustained special education programs and behavior therapy early in life can help children acquire self-care, social, and job skills. Available approaches include applied behavior analysis, developmental models, structured teaching, speech and language therapy, social skills therapy, and occupational therapy. Among these approaches, interventions either treat autistic features comprehensively, or focus treatment on a specific area of deficit. Generally, when educating those with autism, specific tactics may be used to effectively relay information to these individuals. Using as much social interaction as possible is key in targeting the inhibition autistic individuals experience concerning person-to-person contact. Additionally, research has shown that employing semantic groupings, which involves assigning words to typical conceptual categories, can be beneficial in fostering learning.

There has been increasing attention to the development of evidence-based interventions for young children with ASD. Two theoretical frameworks outlined for early childhood intervention include applied behavioral analysis (ABA) and the developmental social-pragmatic model (DSP). Although ABA therapy has a strong evidence base, particularly in regard to early intensive home-based therapy, ABA's effectiveness may be limited by diagnostic severity and IQ of the person affected by ASD. The Journal of Clinical Child and Adolescent Psychology has deemed two early childhood interventions as "well-established": individual comprehensive ABA, and focused teacher-implemented ABA combined with DSP.

Another evidence-based intervention that has demonstrated efficacy is a parent training model, which teaches parents how to implement various ABA and DSP techniques themselves. Various DSP programs have been developed to explicitly deliver intervention systems through at-home parent implementation. 

A multitude of unresearched alternative therapies have also been implemented. Many have resulted in harm to autistic people and should not be employed unless proven to be safe.

In October 2015, the American Academy of Pediatrics (AAP) proposed new evidence-based recommendations for early interventions in ASD for children under 3. These recommendations emphasize early involvement with both developmental and behavioral methods, support by and for parents and caregivers, and a focus on both the core and associated symptoms of ASD.

Epidemiology

The U.S. Center for Disease Control's most recent estimate is that 1 out of every 68 children, or 14.7 per 1,000, are affected by some form of ASD as of 2010. Reviews tend to estimate a prevalence of 6 per 1,000 for autism spectrum disorders as a whole, although prevalence rates vary for each of the developmental disorders in the spectrum. Autism prevalence has been estimated at 1-2 per 1,000, Asperger syndrome at roughly 0.6 per 1,000, childhood disintegrative disorder at 0.02 per 1,000, and PDD-NOS at 3.7 per 1,000. These rates are consistent across cultures and ethnic groups, as autism is considered a universal disorder.

While rates of autism spectrum disorders are consistent across cultures, they vary greatly by gender, with boys affected far more frequently than girls. The average male-to-female ratio for ASDs is 4.2:1, affecting 1 in 70 boys, but only 1 in 315 girls. Girls, however, are more likely to have associated cognitive impairment. Among those with an ASD and intellectual disability, the sex ratio may be closer to 2:1. Prevalence differences may be a result of gender differences in expression of clinical symptoms, with women and girls with autism showing less atypical behaviors and, therefore, less likely to receive an ASD diagnosis.

History

Controversies have surrounded various claims regarding the etiology of autism spectrum disorders. In the 1950s, the "refrigerator mother theory" emerged as an explanation for autism. The hypothesis was based on the idea that autistic behaviors stem from the emotional frigidity, lack of warmth, and cold, distant, rejecting demeanor of a child's mother. Naturally, parents of children with an autism spectrum disorder suffered from blame, guilt, and self-doubt, especially as the theory was embraced by the medical establishment and went largely unchallenged into the mid-1960s. The "refrigerator mother" theory has since continued to be refuted in scientific literature, including a 2015 systematic review which showed no association between caregiver interaction and language outcomes in ASD.

Another controversial claim suggests that watching extensive amounts of television may cause autism. This hypothesis was largely based on research suggesting that the increasing rates of autism in the 1970s and 1980s were linked to the growth of cable television at this time.

Caregivers

Families who care for an autistic child face added stress from a number of different causes. Parents may struggle to understand the diagnosis and to find appropriate care options. Parents often take a negative view of the diagnosis, and may struggle emotionally. In the words of one parent whose two children were both diagnosed with autism, "In the moment of diagnosis, it feels like the death of your hopes and dreams." More than half of parents over the age of 50 are still living with their child as about 85% of people with ASD have difficulties living independently.

Autism rights movement

The autism rights movement is a social movement within the context of disability rights that emphasizes the concept of neurodiversity, viewing the autism spectrum as a result of natural variations in the human brain rather than a disorder to be cured. The autism rights movement advocates for including greater acceptance of autistic behaviors; therapies that focus on coping skills rather than imitating the behaviors of those without autism; and the recognition of the autistic community as a minority group. Autism rights or neurodiversity advocates believe that the autism spectrum is genetic and should be accepted as a natural expression of the human genome. This perspective is distinct from two other likewise distinct views: the medical perspective, that autism is caused by a genetic defect and should be addressed by targeting the autism gene(s), and fringe theories that autism is caused by environmental factors such as vaccines. A common criticism against autistic activists is that the majority of them are "high-functioning" or have Asperger syndrome and do not represent the views of "low-functioning" autistic people.

Academic performance

The number of students identified and served as eligible for autism services in the United States has increased from 5,413 children in 1991-1992 to 370,011 children in the 2010-2011 academic school year. The United States Department of Health and Human Services reported approximately 1 in 68 children at age 8 are diagnosed with autism spectrum disorder (ASD) although onset is typically between ages 2 and 4.

The increasing number of students with ASD in the schools presents significant challenges to teachers, school psychologists, and other school professionals. These challenges include developing a consistent practice that best support the social and cognitive development of the increasing number of students with ASD. Although there is considerable research addressing assessment, identification, and support services for children with ASD, there is a need for further research focused on these topics within the school context. Further research on appropriate support services for students with ASD will provide school psychologists and other education professionals with specific directions for advocacy and service delivery that aim to enhance school outcomes for students with ASD.

Attempts to identify and use best intervention practices for students with autism also pose a challenge due to overdependence on popular or well-known interventions and curricula. Some evidence suggests that although these interventions work for some students, there remains a lack of specificity for which type of student, under what environmental conditions (one-on-one, specialized instruction or general education) and for which targeted deficits they work best. More research is needed to identify what assessment methods are most effective for identifying the level of educational needs for students with ASD. 

A difficulty for academic performance in students with ASD, is the tendency to generalize learning. Learning is different for each student, which is the same for students with ASD. To assist in learning, accommodations are commonly put into place for students with differing abilities. The existing schema of these students works in different ways and can be adjusted to best support the educational development for each student.

Employment

About half of autistics are unemployed, and one third of those with graduate degrees may be unemployed. Among those on the autism spectrum who find work, most are employed in sheltered settings working for wages below the national minimum. While employers state hiring concerns about productivity and supervision, experienced employers of autistics give positive reports of above average memory and detail orientation as well as a high regard for rules and procedure in autistic employees. A majority of the economic burden of autism is caused by lost productivity in the job market. Some studies also find decreased earning among parents who care for autistic children. Adding content related to autism in existing diversity training can clarify misconceptions, support employees, and help provide new opportunities for autistics.

Gene

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Gene Chromosome ...