A proposition is a statement that can be either true or false. It is a central concept in the philosophy of language, semantics, logic, and related fields. Propositions are the objectsdenoted by declarative sentences; for example, "The sky is blue" expresses the proposition that the sky is blue. Unlike sentences, propositions are not linguistic expressions, so the English sentence "Snow is white" and the German "Schnee ist weiß" denote the same proposition. Propositions also serve as the objects of belief and other propositional attitudes, such as when someone believes that the sky is blue.
Formally, propositions are often modeled as functions which map a possible world to a truth value. For instance, the proposition that the sky is blue can be modeled as a function which would return the truth value if given the actual world as input, but would return
if given some alternate world where the sky is green. However, a number
of alternative formalizations have been proposed, notably the structured propositions view.
Propositions have played a large role throughout the history of logic, linguistics, philosophy of language, and related disciplines. Some researchers have doubted whether a consistent definition of propositionhood is possible, David Lewis
even remarking that "the conception we associate with the word
‘proposition’ may be something of a jumble of conflicting desiderata".
The term is often used broadly and has been used to refer to various
related concepts.
Relation to the mind
In relation to the mind, propositions are discussed primarily as they fit into propositional attitudes. Propositional attitudes are simply attitudes characteristic of folk psychology
(belief, desire, etc.) that one can take toward a proposition (e.g. 'it
is raining,' 'snow is white,' etc.). In English, propositions usually
follow folk psychological attitudes by a "that clause" (e.g. "Jane
believes that it is raining"). In philosophy of mind and psychology,
mental states are often taken to primarily consist in propositional
attitudes. The propositions are usually said to be the "mental content"
of the attitude. For example, if Jane has a mental state of believing
that it is raining, her mental content is the proposition 'it is
raining.' Furthermore, since such mental states are about something (namely, propositions), they are said to be intentional mental states.
Explaining the relation of propositions to the mind is especially
difficult for non-mentalist views of propositions, such as those of the
logical positivists and Russell described above, and Gottlob Frege's view that propositions are Platonist entities, that is, existing in an abstract, non-physical realm. So some recent views of propositions have taken them to be mental.
Although propositions cannot be particular thoughts since those are not
shareable, they could be types of cognitive events or properties of thoughts (which could be the same across different thinkers).
Philosophical debates surrounding propositions as they relate to
propositional attitudes have also recently centered on whether they are
internal or external to the agent, or whether they are mind-dependent or
mind-independent entities. For more, see the entry on internalism and externalism in philosophy of mind.
In modern logic
In modern logic, propositions are standardly understood semantically as indicator functions that take a possible world and return a truth value. For example, the proposition that the sky is blue could be represented as a function such that for every world if any, where the sky is blue, and for every world if any, where it is not. A proposition can be modeled equivalently with the inverse image of under the indicator function, which is sometimes called the characteristic set of the proposition. For instance, if and are the only worlds in which the sky is blue, the proposition that the sky is blue could be modeled as the set .
Numerous refinements and alternative notions of proposition-hood have been proposed including inquisitive propositions and structured propositions. Propositions are called structured propositions if they have constituents, in some broad sense. Assuming a structured view of propositions, one can distinguish between singular propositions (also Russellian propositions, named after Bertrand Russell) which are about a particular individual, general propositions, which are not about any particular individual, and particularized propositions, which are about a particular individual but do not contain that individual as a constituent.
Objections to propositions
Attempts to provide a workable definition of proposition include the following:
Two meaningful declarative sentences express the same proposition, if and only if they mean the same thing.
which defines proposition in terms of synonymity. For example,
"Snow is white" (in English) and "Schnee ist weiß" (in German) are
different sentences, but they say the same thing, so they express the
same proposition. Another definition of proposition is:
Two meaningful declarative sentence-tokens express the same proposition, if and only if they mean the same thing.
The above definitions can result in two identical
sentences/sentence-tokens appearing to have the same meaning, and thus
expressing the same proposition and yet having different truth-values,
as in "I am Spartacus" said by Spartacus and said by John Smith, and "It
is Wednesday" said on a Wednesday and on a Thursday. These examples
reflect the problem of ambiguity
in common language, resulting in a mistaken equivalence of the
statements. "I am Spartacus" spoken by Spartacus is the declaration that
the individual speaking is called Spartacus and it is true. When spoken
by John Smith, it is a declaration about a different speaker and it is
false. The term "I" means different things, so "I am Spartacus" means
different things.
A related problem is when identical sentences have the same
truth-value, yet express different propositions. The sentence "I am a
philosopher" could have been spoken by both Socrates and Plato. In both
instances, the statement is true, but means something different.
These problems are addressed in predicate logic
by using a variable for the problematic term, so that "X is a
philosopher" can have Socrates or Plato substituted for X, illustrating
that "Socrates is a philosopher" and "Plato is a philosopher" are
different propositions. Similarly, "I am Spartacus" becomes "X is
Spartacus", where X is replaced with terms representing the individuals
Spartacus and John Smith.
In other words, the example problems can be averted if sentences
are formulated with precision such that their terms have unambiguous
meanings.
A number of philosophers and linguists claim that all definitions
of a proposition are too vague to be useful. For them, it is just a
misleading concept that should be removed from philosophy and semantics. W. V. Quine, who granted the existence of sets in mathematics, maintained that the indeterminacy of translation prevented any
meaningful discussion of propositions, and that they should be discarded
in favor of sentences.
Statements
In logic and semantics, the term statement is variously understood to mean either:
a proposition. Which is the assertion that is made by (i.e., the meaning of) a true or false declarative sentence.
In the latter case, a (declarative) sentence is just one way of
expressing an underlying statement. A statement is what a sentence
means, it is the notion or idea that a sentence expresses, i.e., what it
represents. For example, it could be said that "2 + 2 = 4" and "two
plus two equals four" are two different sentences expressing the same
statement. As another example, consider that the Arabic numeral '7', the Roman numeral 'VII', and the English word 'seven' are all distinct from the underlying number.
Philosopher of languagePeter Strawson
(1919–2006) advocated the use of the term "statement" in sense (2) in
preference to proposition. Strawson used the term "statement" to make
the point that two declarative sentences can make the same statement if
they say the same thing in different ways. Thus, in the usage advocated
by Strawson, "All men are mortal." and "Every man is mortal." are two
different sentences that make the same statement.
In either case, a statement is viewed as a truth bearer.
Examples of sentences that are (or make) true statements:
"Socrates is a man."
"A triangle has three sides."
"Madrid is the capital of Spain."
Examples of sentences that are also statements, even though they aren't true:
"All toasters are made of solid gold."
"Two plus two equals five."
Examples of sentences that are not (or do not make) statements:
The first two examples are not declarative sentences and therefore
are not (or do not make) statements.
The third and fourth are declarative sentences but, lacking meaning, are
neither true nor false and therefore are not (or do not make)
statements. The fifth and sixth examples are meaningful declarative
sentences, but are not statements but rather matters of opinion or
taste. Whether or not the sentence "Pegasus exists." is a statement is a
subject of debate among philosophers. Bertrand Russell held that it is a (false) statement. Strawson held it is not a statement at all.
As an abstract entity
In
some treatments, "statement" is introduced in order to distinguish a
sentence from its informational content. A statement is regarded as the
information content of an information-bearing sentence. Thus, a sentence
is related to the statement it bears like a numeral to the number it
refers to. Statements are abstract logical entities, while sentences are grammatical entities.
Historical usage
By Aristotle
In Aristotelian logic a proposition was defined as a particular kind of sentence (a declarative sentence) that affirms or denies a predicate of a subject, optionally with the help of a copula. Aristotelian propositions take forms like "All men are mortal" and "Socrates is a man."
Aristotelian logic identifies a categorical proposition as a sentence which affirms or denies a predicate of a subject, optionally with the help of a copula.
An Aristotelian proposition may take the form of "All men are mortal"
or "Socrates is a man." In the first example, the subject is "men",
predicate is "mortal" and copula is "are", while in the second example,
the subject is "Socrates", the predicate is "a man" and copula is "is".
Some philosophers argue that some (or all) kinds of speech or
actions besides the declarative ones also have propositional content.
For example, yes–no questions present propositions, being inquiries into the truth value of them. On the other hand, some signs
can be declarative assertions of propositions, without forming a
sentence nor even being linguistic (e.g. traffic signs convey definite
meaning which is either true or false).
Propositions are also spoken of as the content of beliefs and similar intentional attitudes, such as desires, preferences, and hopes. For example, "I desire that I have a new car", or "I wonder whether it will snow"
(or, whether it is the case that "it will snow"). Desire, belief,
doubt, and so on, are thus called propositional attitudes when they take
this sort of content.
By Russell
Bertrand Russell held that propositions were structured entities with objects and properties as constituents. One important difference between Ludwig Wittgenstein's view (according to which a proposition is the set of possible worlds/states
of affairs in which it is true) is that on the Russellian account, two
propositions that are true in all the same states of affairs can still
be differentiated. For instance, the proposition "two plus two equals
four" is distinct on a Russellian account from the proposition "three
plus three equals six". If propositions are sets of possible worlds,
however, then all mathematical truths (and all other necessary truths)
are the same set (the set of all possible worlds).
Amino acids are the building blocks of protein.Amino
acids are necessary nutrients. Present in every cell, they are also
precursors to nucleic acids, co-enzymes, hormones, immune response,
repair and other molecules essential for life.
After water, proteins account for more mass in an organism than any other type of molecule. Protein is present in every cell, and it is a structural component of every body tissue and organ, including hair, skin, blood, and bone. Protein is especially abundant in muscle. Cellular messengers (hormones) and transport molecules are constructed from proteins, including enzymes and antibodies, as are cell membrane components, such as glycoproteins, G proteins, and ion channels. The types of amino acids and their sequence determine the unique 3-dimensional structure and function of a protein.
Protein milkshakes, made from protein powder (center) and milk (left), are a common bodybuilding supplement
Protein occurs in a wide range of food. On a worldwide basis, plant protein foods contribute over 60% of the per capita supply of protein. In North America, animal-derived foods contribute about 70% of protein sources. Insects are a source of protein in many parts of the world. In parts of Africa, up to 50% of dietary protein derives from insects. It is estimated that more than 2 billion people eat insects daily.
Meat, dairy, eggs, soybeans, fish, whole grains, and cereals are sources of protein. Examples of food staples
and cereal sources of protein, each with a concentration greater than
7%, are (in no particular order) buckwheat, oats, rye, millet, maize
(corn), rice, wheat, sorghum, amaranth, and quinoa. Game meat is an affordable protein source in some countries.
Photovoltaic-driven microbial protein
production uses electricity from solar panels and carbon dioxide from
the air to create fuel for microbes, which are grown in bioreactor vats
and then processed into dry protein powders. The process makes highly
efficient use of land, water and fertiliser.
Testing in foods
Nitrogen-based crude protein
The classic assays for protein concentration in food are the Kjeldahl method and the Dumas method.
These tests determine the total nitrogen in a sample. The only major
component of most food which contains nitrogen is protein (fat,
carbohydrate and dietary fiber do not contain nitrogen). If the amount
of nitrogen is multiplied by a factor depending on the kinds of protein
expected in the food the total protein can be determined. This value is
known as the "crude protein" content. The use of correct
conversion factors is heavily debated, specifically with the
introduction of more plant-derived protein products. However, on food labels the protein is calculated as the amount of
nitrogen multiplied by 6.25, because the average nitrogen content of
proteins is about 16%. The Kjeldahl test is typically used, because it
is the method the AOAC International
has adopted and is therefore used by many food standards agencies
around the world, though the Dumas method is also approved by some
standards organizations.
Nitrogen-based protein measurement cannot distinguish between true protein and non-protein nitrogen (NPN). NPN occurs in significant amounts in milk, edible insects, and fish. In addition, accidental contamination
and intentional adulteration of protein meals with NPN sources that
inflate crude protein content measurements have been known to occur in
the food industry for decades. To ensure food quality, purchasers of protein meals routinely conduct quality control tests designed to detect the most common non-protein nitrogen contaminants, such as urea and ammonium nitrate.
In
at least one segment of the food industry, the dairy industry, some
countries (at least the U.S., Australia, France and Hungary) have
adopted "true protein" measurement, as opposed to crude protein
measurement, as the standard for payment and testing: "True protein is a
measure of only the proteins in milk, whereas crude protein is a
measure of all sources of nitrogen and includes nonprotein nitrogen,
such as urea, which has no food value to humans. ... Current
milk-testing equipment measures peptide bonds, a direct measure of true
protein." Measuring peptide bonds in grains has also been put into practice in
several countries including Canada, the UK, Australia, Russia and
Argentina where near-infrared reflectance (NIR) technology, a type of infrared spectroscopy is used.
The more traditional approach to true protein analysis is amino
acid analysis. Data from such analysis has additional nutritional
meaning, as humans and other animals have specific requirements for
essential amino acids. The Food and Agriculture Organization of the United Nations (FAO) recommends that only amino acid analysis be used to determine protein in, inter alia,
foods used as the sole source of nourishment, such as infant formula,
but also provides: "When data on amino acids analyses are not available,
determination of protein based on total N content by Kjeldahl (AOAC,
2000) or similar method ... is considered acceptable." Using standard methods for amino acid analysis, the true protein content can be reported as the sum of the anhydrous masses of all 18 amino acids analyzed. AA analysis can be performed using standard methods including ISO 13903 (2005) and AOAC 988.15.
In the context of dairy products, NPN can also be calculated by
precipitating away all protein and measuring the nitrogen content in the
remaining fraction.
Ruminant metabolizable protein
The
testing method for protein in beef cattle feed has grown into a science
over the post-war years. The standard text in the United States, Nutrient Requirements of Beef Cattle, has been through eight editions over at least seventy years. The 1996 sixth edition substituted for the fifth edition's crude protein the concept of "metabolizeable protein", which was defined around the year 2000 as "the true protein absorbed by the intestine, supplied by microbial protein and undegraded intake protein". (This refers specifically to ruminant nutrition, where microbes living in the rumen can convert NPNs to proteins. Such conversion does not happen in non-ruminants such as humans.)
The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition. There are multiple systems which rate proteins by their usefulness to
an organism based on their relative percentage of amino acids and, in
some systems, the digestibility of the protein source. They include biological value, net protein utilization, and PDCAAS (Protein Digestibility Corrected Amino Acids Score) which was developed by the FDA as a modification of the Protein efficiency ratio
(PER) method. The PDCAAS rating was adopted by the US Food and Drug
Administration (FDA) and the Food and Agricultural Organization of the
United Nations/World Health Organization
(FAO/WHO) in 1993 as "the preferred 'best'" method to determine protein
quality. These organizations have suggested that other methods for
evaluating the quality of protein are inferior.
Most proteins are decomposed to single amino acids by digestion in the gastro-intestinal tract.
Digestion typically begins in the stomach when pepsinogen is converted to pepsin by the action of hydrochloric acid, and continued by trypsin and chymotrypsin in the small intestine. Before the absorption in the small intestine,
most proteins are already reduced to single amino acid or peptides of
several amino acids. Most peptides longer than four amino acids are not
absorbed. Absorption into the intestinal absorptive cells is not the end. There, most of the peptides are broken into single amino acids.
Absorption of the amino acids and their derivatives into which dietary protein is degraded is done by the gastrointestinal tract.
The absorption rates of individual amino acids are highly dependent on
the protein source; for example, the digestibilities of many amino acids
in humans, the difference between soy and milk proteins and between individual milk proteins, beta-lactoglobulin and casein. For milk proteins, about 50% of the ingested protein is absorbed between the stomach and the jejunum and 90% is absorbed by the time the digested food reaches the ileum. Biological value (BV) is a measure of the proportion of absorbed
protein from a food which becomes incorporated into the proteins of the
organism's body.
Newborn
Newborns of mammals are exceptional in protein digestion and assimilation in that they can absorb intact proteins at the small intestine. This enables passive immunity, i.e., transfer of immunoglobulins from the mother to the newborn, via milk.
Considerable debate has taken place regarding protein intake requirements. The amount of protein required in a person's diet is determined in
large part by overall energy intake, the body's need for nitrogen and
essential amino acids, body weight and composition, rate of growth in
the individual, physical activity level, the individual's energy and
carbohydrate intake, and the presence of illness or injury. Physical activity and exertion as well as enhanced muscular mass
increase the need for protein. Requirements are also greater during
childhood for growth and development, during pregnancy, or when
breastfeeding in order to nourish a baby or when the body needs to
recover from malnutrition or trauma or after an operation.
Dietary recommendations
According to US & Canadian Dietary Reference Intake
guidelines, women ages 19–70 need to consume 46 grams of protein per
day while men ages 19–70 need to consume 56 grams of protein per day to
minimize risk of deficiencies. These Recommended Dietary Allowances
(RDAs) were calculated based on 0.8 grams protein per kilogram body
weight and average body weights of 57 kg (126 pounds) and 70 kg (154
pounds), respectively. However, this recommendation is based on structural requirements but disregards use of protein for energy metabolism. This requirement is for a normal sedentary person. In the United States, average protein consumption is higher than the
RDA. According to results of the National Health and Nutrition
Examination Survey (NHANES 2013–2014), average protein consumption for
women ages 20 and older was 69.8 grams and for men 98.3 grams/day. According to research from Harvard University, the National Academy of Medicine suggests that adults should consume at least 0.8 grams of protein per
kilogram of body weight daily, which is roughly equivalent to a little
more than 7 grams for every 20 pounds of body weight. This
recommendation is widely accepted by health professionals as a guideline
for maintaining muscle mass, supporting metabolic functions, and
promoting overall health.
Active people
Several
studies have concluded that active people and athletes may require
elevated protein intake (compared to 0.8 g/kg) due to increase in muscle
mass and sweat losses, as well as need for body repair and energy
source. Indeed, it has been shown that protein contribute around 3% of the total energy expenditure during exercise. Suggested amounts vary from 1.2 to 1.4 g/kg for those doing endurance exercise to as much as 1.6-1.8 g/kg for strength exercise and up to 2.0 g/kg/day for older people, while a proposed maximum daily protein intake would be approximately 25% of energy requirements i.e. approximately 2 to 2.5 g/kg. However, many questions still remain to be resolved.
In addition, some have suggested that athletes using restricted-calorie
diets for weight loss should further increase their protein
consumption, possibly to 1.8–2.0 g/kg, in order to avoid loss of lean
muscle mass.
Aerobic exercise protein needs
Endurance
athletes differ from strength-building athletes in that endurance
athletes do not build as much muscle mass from training as
strength-building athletes do. Research suggests that individuals performing endurance activity
require more protein intake than sedentary individuals so that muscles
broken down during endurance workouts can be repaired. Although the protein requirement for athletes still remains
controversial (for instance see Lamont, Nutrition Research Reviews,
pages 142 - 149, 2012), research does show that endurance athletes can
benefit from increasing protein intake because the type of exercise
endurance athletes participate in still alters the protein metabolism
pathway. The overall protein requirement increases because of amino acid
oxidation in endurance-trained athletes. Endurance athletes who exercise over a long period (2–5 hours per
training session) use protein as a source of 5–10% of their total energy
expended. Therefore, a slight increase in protein intake may be
beneficial to endurance athletes by replacing the protein lost in energy
expenditure and protein lost in repairing muscles. One review concluded
that endurance athletes may increase daily protein intake to a maximum
of 1.2–1.4 g per kg body weight.
Anaerobic exercise protein needs
Research also indicates that individuals performing strength training
activity require more protein than sedentary individuals.
Strength-training athletes may increase their daily protein intake to a
maximum of 1.4–1.8 g per kg body weight to enhance muscle protein
synthesis, or to make up for the loss of amino acid oxidation during
exercise. Many athletes maintain a high-protein diet
as part of their training. In fact, some athletes who specialize in
anaerobic sports (e.g., weightlifting) believe a very high level of
protein intake is necessary, and so consume high protein meals and also
protein supplements.
A food allergy is an abnormal immune response to proteins in food. The signs and symptoms may range from mild to severe. They may include itchiness,
swelling of the tongue, vomiting, diarrhea, hives, trouble breathing,
or low blood pressure. These symptoms typically occurs within minutes to
one hour after exposure. When the symptoms are severe, it is known as anaphylaxis. The following eight foods are responsible for about 90% of allergic reactions: cow's milk, eggs, wheat, shellfish, fish, peanuts, tree nuts and soy.
Chronic kidney disease
While there is no conclusive evidence that a high protein diet can cause chronic kidney disease,
there is a consensus that people with this disease should decrease
consumption of protein. According to one 2009 review updated in 2018,
people with chronic kidney disease who reduce protein consumption have
less likelihood of progressing to end stage kidney disease. Moreover, people with this disease while using a low protein diet (0.6 g/kg/d - 0.8 g/kg/d) may develop metabolic compensations that preserve kidney function, although in some people, malnutrition may occur.
Phenylketonuria
Individuals with phenylketonuria
(PKU) must keep their intake of phenylalanine – an essential amino
acid – extremely low to prevent a mental disability and other metabolic
complications. Phenylalanine is a component of the artificial sweetener
aspartame, so people with PKU need to avoid low calorie beverages and
foods with this ingredient.
The U.S. and Canadian Dietary Reference Intake review for protein
concluded that there was not sufficient evidence to establish a Tolerable upper intake level, i.e., an upper limit for how much protein can be safely consumed.
When amino acids are in excess of needs, the liver takes up the amino acids and deaminates them, a process converting the nitrogen from the amino acids into ammonia, further processed in the liver into urea via the urea cycle. Excretion of urea occurs via the kidneys. Other parts of the amino acid molecules can be converted into glucose and used for fuel. When food protein intake is periodically high or low, the body tries to
keep protein levels at an equilibrium by using the "labile protein
reserve" to compensate for daily variations in protein intake. However,
unlike body fat as a reserve for future caloric needs, there is no
protein storage for future needs.
Excessive protein intake may increase calcium excretion in urine,
occurring to compensate for the pH imbalance from oxidation of sulfur
amino acids. This may lead to a higher risk of kidney stone formation
from calcium in the renal circulatory system. One meta-analysis reported no adverse effects of higher protein intakes on bone density. Another meta-analysis reported a small decrease in systolic and
diastolic blood pressure with diets higher in protein, with no
differences between animal and plant protein.
High protein diets have been shown to lead to an additional
1.21 kg of weight loss over a period of 3 months versus a baseline
protein diet in a meta-analysis. Benefits of decreased body mass index as well as HDL cholesterol
were more strongly observed in studies with only a slight increase in
protein intake rather where high protein intake was classified as 45% of
total energy intake. Detrimental effects to cardiovascular activity were not observed in
short-term diets of 6 months or less. There is little consensus on the
potentially detrimental effects to healthy individuals of a long-term
high protein diet, leading to caution advisories about using high
protein intake as a form of weight loss.
The 2015–2020 Dietary Guidelines for Americans (DGA)
recommends that men and teenage boys increase their consumption of
fruits, vegetables and other under-consumed foods, and that a means of
accomplishing this would be to reduce overall intake of protein foods. The 2015–2020 DGA report does not set a recommended limit for the
intake of red and processed meat. While the report acknowledges research
showing that lower intake of red and processed meat is correlated with
reduced risk of cardiovascular diseases
in adults, it also notes the value of nutrients provided from these
meats. The recommendation is not to limit intake of meats or protein,
but rather to monitor and keep within daily limits the sodium (<
2300 mg), saturated fats
(less than 10% of total calories per day), and added sugars (less than
10% of total calories per day) that may be increased as a result of
consumption of certain meats and proteins. While the 2015 DGA report
does advise for a reduced level of consumption of red and processed
meats, the 2015–2020 DGA key recommendations recommend that a variety of
protein foods be consumed, including both vegetarian and non-vegetarian
sources of protein.
Protein deficiency and malnutrition (PEM) can lead to a variety of ailments, including Intellectual disability and kwashiorkor. Symptoms of kwashiorkor include apathy, diarrhea, inactivity, failure
to grow, flaky skin, fatty liver, and edema of the belly and legs. This
edema is explained by the action of lipoxygenase on arachidonic acid to
form leukotrienes and the normal functioning of proteins in fluid
balance and lipoprotein transport.
PEM is fairly common worldwide in both children and adults and
accounts for 6 million deaths annually. In the industrialized world, PEM
is predominantly seen in hospitals, is associated with disease, or is
often found in the elderly.
Royal jelly is a honey bee secretion that is used in the nutrition of larvae and adult queens. It is secreted from the glands in the hypopharynx of nurse bees, and fed to all larvae in the colony, regardless of sex or caste.
Queen larva in a cell on a frame with bees
During the process of creating new queens, the workers construct
special queen cells. The larvae in these cells are fed with copious
amounts of royal jelly. This type of feeding in part triggers the
development of queen morphology, including the fully developed ovaries needed to lay eggs. Note however that some newer research shows it is not solely the
presence of royal jelly that develops the queen but rather the absence
of certain other nutrients fed to worker bees.
Royal jelly is sometimes used in alternative medicine under the category apitherapy. It is often sold as a dietary supplement for humans, but the European Food Safety Authority concluded in 2011 that evidence does not support the claim that consuming royal jelly offers health benefits to humans. In the United States, the Food and Drug Administration has taken legal action against companies that have marketed royal jelly products using unfounded claims of health benefits.
Production
Royal
jelly is secreted from the glands in the heads of worker bees and is
fed to all bee larvae, whether they are destined to become drones
(males), workers (sterile females), or queens (fertile females). After
three days, the drone and worker larvae are no longer fed with royal
jelly, but queen larvae continue to be fed this special substance
throughout their development.
Major royal jelly proteins (MRJPs) are a family of proteins secreted
by honey bees. The family consists of nine proteins, of which MRJP1
(also called royalactin), MRJP2, MRJP3, MRJP4, and MRJP5 are present in
the royal jelly secreted by worker bees. MRJP1 is the most abundant, and largest in size. The five proteins constitute 83–90% of the total proteins in royal jelly. They are synthesised by a family of nine genes (mrjp genes), which are in turn members of the yellow family of genes such as in the fruitfly (Drosophila) and bacteria. They are involved in differential development of queen larvae and worker larvae, thus establishing division of labour in the bee colony.
Epigenetic effects
The honey bee queens and workers represent one of the most striking examples of environmentally controlled phenotypicpolymorphism.
Even if two larvae had identical DNA, one raised to be a worker, the
other a queen, the two adults would be strongly differentiated across a
wide range of characteristics including anatomical and physiological
differences, longevity, and reproductive capacity. Queens constitute the female sexual caste and have large active
ovaries, whereas female workers have only rudimentary, inactive ovaries
and are functionally sterile. The queen–worker developmental divide is
controlled epigenetically by differential feeding with royal jelly; this appears to be due specifically to the protein royalactin.
A female larva destined to become a queen is fed large quantities of
royal jelly; this triggers a cascade of molecular events resulting in
development of a queen. It has been shown that this phenomenon is mediated by an epigenetic modification of DNA known as CpG methylation. Silencing the expression of an enzyme that methylates DNA in newly
hatched larvae led to a royal jelly-like effect on the larval
developmental trajectory; the majority of individuals with reduced DNA
methylation levels emerged as queens with fully developed ovaries. This
finding suggests that DNA methylation in honey bees allows the expression of epigenetic information to be differentially altered by nutritional input.
Use by humans
Cultivation
Royal
jelly is harvested by stimulating colonies with movable frame hives to
produce queen bees. Royal jelly is collected from each individual queen
cell (honeycomb)
when the queen larvae are about four days old. These are the only cells
in which large amounts are deposited. This is because when royal jelly
is fed to worker larvae, it is fed directly to them, and they consume it
as it is produced, while the cells of queen larvae are "stocked" with
royal jelly much faster than the larvae can consume it. Therefore, only
in queen cells is the harvest of royal jelly practical.
A well-managed hive during a season of 5–6 months can produce approximately 500 g (18 oz) of royal jelly. Since the product is perishable, producers must have immediate access
to proper cold storage (e.g., a household refrigerator or freezer) in
which the royal jelly is stored until it is sold or conveyed to a
collection center. Sometimes honey or beeswax is added to the royal jelly, which is thought to aid its preservation.
Royal jelly may cause allergic reactions in humans, ranging from hives or asthma (or both), to even fatal anaphylaxis. The incidence of allergic side effects in people who consume royal
jelly is unknown. The risk of having an allergy to royal jelly is higher
in people who have other allergies.
The exact cause of autism, including what was formerly known as Asperger syndrome, is not well understood. While it has high heritability, the underlying genetics have not been determined conclusively. Environmental factors are also believed to play a role. Brain imaging has not identified a common underlying condition. There is no single treatment, and the UK's National Health Service
(NHS) guidelines suggest that "treatment" of any form of autism should
not be a goal, since autism is not "a disease that can be removed or
cured". According to the Royal College of Psychiatrists, while co-occurring conditions might require treatment, "management of
autism itself is chiefly about the provision of the education, training,
and social support/care required to improve the person's ability to
function in the everyday world". The effectiveness of particular
interventions for autism is supported by only limited data. Interventions may include social skills training, cognitive behavioral therapy, physical therapy, speech therapy, parent training, and medications for associated problems, such as mood or anxiety. Autistic characteristics tend to become less obvious in adulthood, but social and communication difficulties usually persist.
In 2015, Asperger syndrome was estimated to affect 37.2 million people globally, or about 0.5% of the population. The exact percentage of people affected has still not been firmly established. Autism spectrum disorder is diagnosed in males more often than females, and females are typically diagnosed at a later age. The modern conception of Asperger syndrome came into existence in 1981 and went through a period of popularization. It became a standardized diagnosis in the 1990s and was merged into ASD in 2013. Many questions and controversies about the condition remain.
Classification
The extent of the overlap between Asperger syndrome and other forms of autism, particularly what was sometimes called high-functioning autism is unclear. The ASD classification is to some extent an artifact of how autism was discovered, and it may not reflect the true nature of the spectrum; methodological problems have beset Asperger syndrome as a valid diagnosis from the outset. As noted above, in the 2010s, Asperger syndrome, as a separate
diagnosis, was eliminated and folded into autism spectrum disorder in
the DSM-5 and the ICD-11. Like the diagnosis of Asperger syndrome, the change was controversial.
The World Health Organization (WHO) previously defined Asperger syndrome (AS) as one of the pervasive developmental disorders (PDD), which are a spectrum of psychological disorders that are characterized by abnormalities of social interaction
and communication that pervade the individual's functioning, and by
restricted and repetitive interests and behavior. Like other
neurodevelopmental conditions, ASD begins in infancy or childhood, has a
steady course without remission or relapse, and has impairments that
result from maturation-related changes in various systems of the brain.
Characteristics
People with Asperger syndrome often display restricted or specialized interests, such as this boy's interest in stacking cans.
As a pervasive developmental disorder,
Asperger syndrome is distinguished by a pattern of symptoms rather than
a single symptom. It is characterized by qualitative impairment in
social interaction, by stereotyped and restricted patterns of behavior,
activities, and interests, and by no clinically significant delay in
cognitive development or general delay in language. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis.
Suicidal thoughts and behaviors are a serious concern within the
autistic population. One study found that adults with Asperger syndrome
exhibited suicidal thoughts at 9 times the rate of the general
population. Of autistic study participants, 66% had experienced suicidal ideation, while 35% had planned or attempted suicide.
A lack of demonstrated empathy affects aspects of social relatability for persons with Asperger syndrome. Individuals with Asperger syndrome experience difficulties in basic
elements of social interaction, which may include a failure to develop
friendships or to seek shared enjoyments or achievements with others
(e.g., showing others objects of interest); a lack of social or
emotional reciprocity; and impaired nonverbal behaviors in areas such as eye contact, facial expression, posture, and gesture.
People with Asperger syndrome may not be as withdrawn around
others, compared with those with other forms of autism; they approach
others, even if awkwardly. For example, a person with Asperger syndrome
may engage in a one-sided, long-winded speech about a favorite topic,
while misunderstanding or not recognizing the listener's feelings or
reactions, such as a wish to change the topic of talk or end the
interaction. This social awkwardness has been called "active but odd". Such failures to react appropriately to social interaction may appear
as disregard for other people's feelings and may come across as rude or
insensitive. However, not all individuals with Asperger syndrome will approach others. Some may even display selective mutism, not speaking at all to most people and excessively to specific others.
The cognitive ability of children with Asperger syndrome often allows them to articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other
people's emotions; however, they typically have difficulty acting on
this knowledge in fluid, real-life situations. People with Asperger syndrome may analyze and distill their
observations of social interaction into rigid behavioral guidelines and
apply these rules in awkward ways, such as forced eye contact, resulting
in a demeanor that appears rigid or socially naïve. A history of failed
attempts to establish reciprocal social relationships can cause
autistic individuals to isolate themselves and cease attempts to engage;
however, autistic people overwhelmingly report a desire for social
contact and friendship.
Violent or criminal behavior
The hypothesis
that individuals with Asperger syndrome are predisposed to violent or
criminal behavior has been investigated but is unsupported by data. More evidence suggests that children diagnosed with Asperger syndrome are more likely to be victims, rather than offenders.
A 2008 review found that about 80% of reported violent criminals with Asperger syndrome also had other coexisting psychotic psychiatric disorders such as schizoaffective disorder. The sample size of this review was small (n = 37).
Empathy
People with an Asperger profile might not be recognized for their empathetic qualities, due to variation in the ways empathy
is felt and expressed. Some people feel deep empathy, but do not
outwardly communicate these sentiments through facial expressions or
language. Some people come to empathy through intellectual processes,
using logic and reasoning to arrive at the feelings. People with
Asperger profiles may be bullied or excluded by peers, and might as a
result be guarded around people, which could appear as lack of empathy.
People with Asperger profiles can still be caring individuals; indeed,
it is particularly common for those with the profile to feel and exhibit
deep concern for individual rights, human welfare, animal rights,
environmental protection, and other global and humanitarian causes.
Evidence suggests that in the "double empathy problem
model, autistic people have a unique interaction style which is
significantly more readable by other autistic people, compared to
non-autistic people."
Restricted and repetitive interests and behavior
People with Asperger syndrome can display behavior, interests, and
activities that are restricted and repetitive and are sometimes
abnormally intense or focused. They may stick to inflexible routines,
move in stereotyped
and repetitive ways, preoccupy themselves with parts of objects, or
engage in compulsive behaviors like lining objects up to form patterns.
The pursuit of specific and narrow areas of interest is one of the most striking among possible features of AS. Individuals with AS may collect volumes of detailed information on a
relatively narrow topic such as weather data or star names without
necessarily having a genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. This behavior is usually apparent by age five or six. Although these special interests
may change from time to time, they typically become more unusual and
narrowly focused and often dominate social interaction so much that the
entire family may become immersed. Because narrow topics often capture
the interest of children, this symptom may go unrecognized.
Stereotyped and repetitive motor behaviors, called stimming, are a core part of the diagnosis of AS and other ASDs. Stims are believed to be used for self-soothing and regulate sensory input. They include hand movements such as flapping or twisting, and complex whole-body movements. These are typically repeated in longer bursts and look more voluntary or ritualistic than tics, which are usually faster, less rhythmical, and less often symmetrical. Stimming may have a connection with tics, and studies have reported a consistent comorbidity between AS and Tourette syndrome in the range of 8–20%,with one figure as high as 80% for tics of some kind or another, for which several explanations have been put forward, including common genetic factors and dopamine, glutamate, or serotonin abnormalities.
According to the Adult Asperger Assessment (AAA) diagnostic test,
a lack of interest in fiction and a positive preference towards
non-fiction is common among adults with AS.
Speech and language
Although individuals with Asperger syndrome acquire language skills
without significant general delay and their speech typically lacks
significant abnormalities; language acquisition and use is often atypical. Abnormalities include verbosity, abrupt transitions, literal
interpretations and miscomprehension of nuance, use of metaphor
meaningful only to the speaker, auditory perception deficits; unusually pedantic, formal, or idiosyncratic speech; and oddities in loudness, pitch, intonation, prosody, and rhythm. Echolalia has also been observed in individuals with AS.
Three aspects of communication patterns are of clinical interest: poor prosody, tangential and circumstantial speech, and marked verbosity. Although inflection
and intonation may be less rigid or monotonic than in classic autism,
people with AS often have a limited range of intonation: speech may be
unusually fast, jerky, or loud. Speech may convey a sense of incoherence; the conversational style often includes monologues about topics that bore the listener, fails to provide context
for comments, or fails to suppress internal thoughts. Individuals with
AS may fail to detect whether the listener is interested or engaged in
the conversation. The speaker's conclusion or point may never be made,
and attempts by the listener to elaborate on the speech's content or
logic, or to shift to related topics, are often unsuccessful.
Children with AS may have a sophisticated vocabulary at a young
age and such children have often been colloquially called "little
professors" but have difficulty understanding figurative language and tend to use language literally. Children with AS appear to have particular weaknesses in areas of nonliteral language that include humor, irony, teasing, and sarcasm.
Although individuals with AS usually understand the cognitive basis of
humor, they seem to lack understanding of the intent of humor to share
the enjoyment with others. Despite strong evidence of impaired humor appreciation, anecdotal
reports of humor in individuals with AS seem to challenge some
psychological theories of AS and autism.
Motor and sensory perception
Individuals with Asperger syndrome may have signs or symptoms that
are independent of the diagnosis but can affect the individual or the
family. These include differences in perception and problems with motor skills, sleep, and emotions.
Individuals with AS often have excellent auditory and visual perception. Children with ASD often demonstrate enhanced perception of small
changes in patterns such as arrangements of objects or well-known
images; typically this is domain-specific and involves processing of
fine-grained features. Conversely, compared with individuals with high-functioning autism,
individuals with AS have deficits in some tasks involving visual-spatial
perception, auditory perception, or visual memory. Many accounts of individuals with AS and ASD report other unusual sensory and perceptual skills and experiences. They may be unusually sensitive or insensitive to sound, light, and other stimuli; these sensory responses are found in other developmental disorders and
are not specific to AS or to ASD. There is little support for increased fight-or-flight response or failure of habituation in autism; there is more evidence of decreased responsiveness to sensory stimuli, although several studies show no differences.
Hans Asperger's initial accounts and other diagnostic schemes include descriptions of physical clumsiness. Children with AS may be delayed in acquiring skills requiring dexterity,
such as riding a bicycle or opening a jar, and may seem to move
awkwardly or feel "uncomfortable in their own skin". They may be poorly
coordinated or have an odd or bouncy gait or posture, poor handwriting,
or problems with motor coordination. They may show problems with proprioception (sensation of body position) on measures of developmental coordination disorder (motor planning disorder), balance, tandem gait, and finger-thumb apposition. There is no evidence that these motor skills problems differentiate AS from other high-functioning ASDs.
Children with AS are more likely to have sleep problems, including difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. AS is also associated with high levels of alexithymia, which is difficulty in identifying and describing one's emotions. Although AS, lower sleep quality, and alexithymia are associated with each other, their causal relationship is unclear.
Hans Asperger described common traits among his patients' family
members, especially fathers, and research supports this observation and
suggests a genetic contribution to Asperger syndrome. Although no
specific genetic factor has yet been identified, multiple factors are
believed to play a role in the expression of autism, given the variability in symptoms seen in children. Hundreds of genes have been linked to AS, and these genes play crucial role in a multitude of biological processes, exerting influence over the maturation and functioning of the brain. Evidence for a genetic link
is that AS tends to run in families where more family members have
limited behavioral symptoms similar to AS (for example, some problems
with social interaction, or with language and reading skills). Most behavioral genetic research suggests that all autism spectrum disorders have shared genetic mechanisms. There may be shared genes in which particular alleles make an individual vulnerable, and varying combinations result in differing severity and symptoms in each person with AS.
A few ASD cases have been linked to exposure to teratogens (agents that cause birth defects) during the first eight weeks from conception.
Although this does not exclude the possibility that ASD can be
initiated or affected later, it is strong evidence that ASD arises very
early in development. Many environmental factors have been hypothesized to act after birth, but none has been confirmed by scientific investigation. These environmental elements can act as independent and significant
risk factors, or they can potentially influence pre-existing genetic
factors in people who have a genetic predisposition.
Asperger syndrome appears to result from developmental factors that
affect many or all functional brain systems, as opposed to localized
effects.
Although the specific underpinnings of AS or factors that
distinguish it from other ASDs are unknown, and no clear pathology
common to individuals with AS has emerged, it is still possible that AS's mechanism is separate from other ASDs.
Neuroanatomical studies and the associations with teratogens strongly suggest that the mechanism includes alteration of brain development soon after conception. Abnormal fetal development
may affect the final structure and connectivity of the brain, resulting
in altered neural circuits controlling thought and behavior. Several theories of mechanism are available; none are likely to provide a complete explanation.
General-processing theories
One general-processing theory is weak central coherence theory, which hypothesizes that a limited ability to see the big picture underlies the central disturbance in ASD. A related theory—enhanced perceptual functioning—focuses more on the superiority of locally oriented and perceptual operations in autistic individuals.
Mirror neuron system (MNS) theory
The mirror neuron system (MNS) theory hypothesizes that alterations to the development of the MNS interfere with imitation and lead to Asperger syndrome's core feature of social impairment. One study found that activation is delayed in the core circuit for imitation in individuals with AS. This theory maps well to social cognition theories like the theory of mind, which hypothesizes that autistic behavior arises from impairments in ascribing mental states to oneself and others; or hyper-systemizing,
which hypothesizes that autistic individuals can systematize internal
operation to handle internal events but are less effective at empathizing when handling events generated by other agents.
Diagnosis
Standard diagnostic criteria require impairment in social interaction
and repetitive and stereotyped patterns of behavior, activities, and
interests, without significant delay in language or cognitive
development. Unlike the international standard, the DSM-IV-TR criteria also required significant impairment in day-to-day functioning; As noted above, in the 2010s, Asperger syndrome, as a separate
diagnosis, was eliminated and folded into autism spectrum disorder in
the DSM-5 and the ICD-11. Other sets of diagnostic criteria have been proposed by Szatmari et al. and by Gillberg and Gillberg.
Diagnosis of ASD (and previously AS) is most commonly made between the ages of four and eleven. A comprehensive assessment involves a multidisciplinary team that observes across multiple settings, and includes neurological and genetic assessment as well as tests for
cognition, psychomotor function, verbal and nonverbal strengths and
weaknesses, style of learning, and skills for independent living. The "gold standard" in diagnosing ASDs combines clinical judgment with the Autism Diagnostic Interview-Revised (ADI-R), a semistructured parent interview; and the Autism Diagnostic Observation Schedule (ADOS), a conversation and play-based interview with the child. Delayed or mistaken diagnosis can be traumatic for individuals and
families; for example, misdiagnosis can lead to medications that worsen
behavior.
Underdiagnosis and overdiagnosis may be problems. The cost and difficulty of screening
and assessment can delay diagnosis. Conversely, the increasing
popularity of drug treatment options and the expansion of benefits has
motivated providers to overdiagnose ASD. There are indications AS has been diagnosed more frequently in recent
years, partly as a residual diagnosis for children of normal
intelligence who are not autistic but have social difficulties.
There are questions about the external validity of the AS diagnosis. That is, it is unclear whether there is a practical benefit in distinguishing AS from autism or PDD-NOS; different screening tools may render different diagnoses for the same person.
Differential diagnosis
Many children with AS are initially misdiagnosed with attention deficit hyperactivity disorder (ADHD). Diagnosing adults is more challenging, as standard diagnostic criteria
are designed for children and the expression of AS changes with age. Adult diagnosis requires painstaking clinical examination and thorough medical history gained from both the individual and other people who know the person, focusing on childhood behavior.
Parents of children with Asperger syndrome can typically trace
differences in their children's development to as early as 30 months of
age. Developmental screening during a routine check-up by a general practitioner or pediatrician may identify signs that warrant further investigation. The United States Preventive Services Task Force in 2016 found it was unclear if screening was beneficial or harmful among children in whom there are no concerns.
Different screening instruments are used to diagnose AS, including the Asperger Syndrome Diagnostic Scale (ASDS); Autism Spectrum Screening Questionnaire (ASSQ); Childhood Autism Spectrum Test (CAST), previously called the Childhood Asperger Syndrome Test; Gilliam Asperger's disorder scale (GADS); Krug Asperger's Disorder Index (KADI); and the autism-spectrum quotient (AQ), with versions for children, adolescents, and adults. None have been shown to reliably differentiate between AS and other ASDs.
Treatment attempts to manage distressing symptoms and to teach
age-appropriate social, communication, and vocational skills that are
not naturally acquired during development. Intervention is tailored to the needs of the individual based on multidisciplinary assessment. Although progress has been made, data supporting the efficacy of particular interventions are limited.
Therapies
Managing ASD may involve multiple therapies that address core
symptoms of the disorder. While many professionals agree that the
earlier the professional support the better, there is no combination
that is recommended above others. Professional support for ASD varies depending on the individual; it
takes into account the linguistic capabilities, verbal strengths, and
nonverbal vulnerabilities of individuals.
Many of those diagnosed with ASD or similar disorders advocate
against behavioral therapies, like Applied behavior analysis (ABA) and
Cognitive behavioral therapy (CBT), often as part of the autism rights movement, on the grounds that these approaches frequently reinforce the demand on autistic people to mask their neurodivergent characteristics or behaviors to favor a more 'neurotypical' and narrow conception of normality. ABA has faced a great deal of criticism over the years. Recently, studies have shown that ABA may be abusive and can increase PTSD symptoms in patients. The Autistic Self Advocacy Network campaigns against the use of ABA in autism.
In the case of CBT and talking therapies, the effectiveness
varies, with many reporting that they appeared 'too self-aware' to gain
significant benefit, as the therapy was designed with neurotypical
people in mind. In autistic children, specifically, they also report that it is only mildly beneficial in aiding with their anxieties.
A typical program of professional support generally includes:
Cognitive behavioral therapy to improve stress management relating to anxiety or explosive emotions and to help reduce obsessive interests (although this may produce
negative impact by demonising special interests) and repetitive
routines;
Of the many studies on behavior-based early intervention programs, most are case reports of up to five participants and typically examine a few problem behaviors such as self-injury, aggression, noncompliance, stereotypies, or spontaneous language; unintended side effects are largely ignored. Despite the popularity of social skills training, its effectiveness is not firmly established. A randomized controlled study of a model for training parents in
problem behaviors in their children with AS showed that parents
attending a one-day workshop or six individual lessons reported fewer
behavioral problems, while parents receiving the individual lessons
reported less intense behavioral problems in their AS children. Vocational training may be important to teach job interview etiquette
and workplace behavior to older children and adults with AS, and
organization software and personal data assistants can improve the work
and life management of people with AS.
Fecal Microbiota Transplantation (FMT) is an innovative therapy for AS that aims to restore microbial balance in the patient's gastrointestinal tract
by introducing healthy fecal microbiota acquired from people with a
diverse microbial composition. This approach attempts to reconstruct the
patient's gut microbiota by taking into account the intricate
interactions between the human gut and the central nervous system via the gut-brain axis (GBA). Any disruption in gut health has been linked to an increased susceptibility to diverse neurodevelopmental disorders.
It is vital to remember that research of AS specifically operates
upon the out-dated classification of this syndrome as external to ASD
(Autism Spectrum Disorder). Similarly, we should also note that ASD is a
spectrum and support varies dramatically depending on the individual.
Medications
No medications directly treat the core symptoms of AS. Although research into the efficacy of pharmaceutical intervention for AS is limited, it is essential to diagnose and treat comorbid conditions. Deficits in self-identifying emotions or in observing effects of one's
behavior on others can make it difficult for individuals with AS to see
why medication may be appropriate. Medication can be effective in combination with behavioral
interventions and environmental accommodations in treating comorbid
symptoms such as anxiety disorders, major depressive disorder,
inattention, and aggression. The atypical antipsychotic medications risperidone, olanzapine and aripiprazole have been shown to reduce the associated symptoms of AS;risperidone can reduce repetitive and self-injurious behaviors,
aggressive outbursts, and impulsivity, and improve stereotypical
patterns of behavior and social relatedness. The selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine, and sertraline have been effective in treating restricted and repetitive interests and behaviors, while stimulant medication, such as methylphenidate, can reduce inattention. In addition, scientists have made a noteworthy finding that oxytocin, a hormone, plays a significant role in shaping human social behavior and the formation of interpersonal connections.
Care must be taken with medications, as side effects may be more
common and harder to evaluate in individuals with AS, and tests of
drugs' effectiveness against comorbid conditions routinely exclude
individuals from the autism spectrum. Abnormalities in metabolism, cardiac conduction times, and an increased risk of type 2 diabetes have been raised as concerns with antipsychotic medications, along with serious long-term neurological side effects. SSRIs can lead to manifestations of behavioral activation such as increased impulsivity, aggression, and sleep disturbance. Weight gain and fatigue are commonly reported side effects of risperidone, which may also lead to increased risk for extrapyramidal symptoms such as restlessness and dystonia and increased serum prolactin levels. Sedation and weight gain are more common with olanzapine, which has also been linked with diabetes. Sedative side-effects in school-age children have ramifications for classroom learning. Individuals with AS may be unable to identify and communicate their internal moods and emotions or to tolerate side effects that for most people would not be problematic.
Prognosis
There is some evidence that children with AS may see a lessening of
symptoms; up to 20% of children may no longer meet the diagnostic
criteria as adults, although social and communication difficulties may
persist. As of 2006,
no studies addressing the long-term outcome of individuals with
Asperger syndrome are available and there are no systematic long-term
follow-up studies of children with AS. Individuals with AS appear to have normal life expectancy, but have an increased prevalence of comorbid psychiatric conditions, such as major depressive disorder and anxiety disorders that may significantly affect prognosis. Although social impairment may be lifelong, the outcome is generally
more positive than with individuals with lower-functioning autism
spectrum disorders; for example, ASD symptoms are more likely to diminish with time in children with AS or forms of autism sometimes described as "high functioning". Most students with AS and forms of autism sometimes seen as "high
functioning" have average mathematical ability and test slightly worse
in mathematics than in general intelligence. However, mathematicians are at least three times more likely to have
autism-spectrum traits than the general population, and are more likely
to have family members with autism.
Although many attend regular education classes, some children with AS may attend special education classes such as separate classroom and resource room because of their social and behavioral difficulties. Adolescents with AS may exhibit ongoing difficulty with self-care
or organization, and disturbances in social and romantic relationships.
Despite high cognitive potential, most young adults with AS remain at
home, yet some do marry and work independently. The "different-ness" adolescents experience can be traumatic. Anxiety may stem from preoccupation over possible violations of
routines and rituals, from being placed in a situation without a clear
schedule or expectations, or from concern with failing in social encounters; the resulting stress may manifest as inattention, withdrawal, reliance on obsessions, hyperactivity, or aggressive or oppositional behavior. Depression is often the result of chronic frustration from repeated failure to engage others socially, and mood disorders requiring treatment may develop. Clinical experience suggests the rate of suicide may be higher among
those with AS, but this has not been confirmed by systematic empirical
studies.
Education of families is critical in developing strategies for understanding strengths and weaknesses; helping the family to cope improves outcomes in children. Prognosis may be improved by diagnosis at a younger age that allows for
early interventions, while interventions in adulthood are valuable but
less beneficial. There are legal implications for individuals with AS as they run the
risk of exploitation by others and may be unable to comprehend the
societal implications of their actions.
Frequency estimates vary enormously. In 2015, it was estimated that 37.2 million people globally are affected. A 2003 review of epidemiological studies
of children found autism rates ranging from 0.03 to 4.84 per 1,000,
with the ratio of autism to Asperger syndrome ranging from 1.5:1 to
16:1; combining the geometric mean ratio of 5:1 with a conservative
prevalence estimate for autism of 1.3 per 1,000 suggests indirectly that
the prevalence of AS might be around 0.26 per 1,000. Part of the variance in estimates arises from differences in diagnostic
criteria. For example, a relatively small 2007 study of 5,484
eight-year-old children in Finland found 2.9 children per 1,000 met the
ICD-10 criteria for an AS diagnosis, 2.7 per 1,000 for Gillberg and
Gillberg criteria, 2.5 for DSM-IV, 1.6 for Szatmari et al., and
4.3 per 1,000 for the union of the four criteria. Boys seem to be more
likely to have AS than girls; estimates of the sex ratio range from
1.6:1 to 4:1, using the Gillberg and Gillberg criteria. Females with autism spectrum disorders may be underdiagnosed.
Anxiety disorders and major depressive disorder are the most common conditions seen at the same time; comorbidity of these in persons with AS is estimated at 65%. Reports have associated AS with medical conditions such as aminoaciduria and ligamentous laxity, but these have been case reports or small studies and no factors have been associated with AS across studies. One study of males with AS found an increased rate of epilepsy and a high rate (51%) of nonverbal learning disorder. AS is associated with tics, Tourette syndrome and bipolar disorder. The repetitive behaviors of AS have many similarities with the symptoms of obsessive–compulsive disorder and obsessive–compulsive personality disorder, and 26% of a sample of young adults with AS were found to meet the criteria for schizoid personality disorder
(which is characterised by severe social seclusion and emotional
detachment), more than any other personality disorder in the sample. However many of these studies are based on clinical samples or lack standardized measures; nonetheless, comorbid conditions are relatively common.
Asperger syndrome was named after the Austrian pediatrician Hans Asperger (1906–1980), but not coined by him. Asperger syndrome was a relatively new diagnosis in the field of autism, though a syndrome like it was described as early as 1925 by Soviet child psychiatrist Grunya Sukhareva (1891–1981). As a child, Asperger appears to have exhibited some features of the
very condition named after him, such as remoteness and talent in
language. In 1944, Asperger gave detailed descriptions of four representative children in his practice who had difficulty in integrating themselves socially and showing
empathy towards peers. They also lacked nonverbal communication skills
and were physically clumsy. Asperger described this "autistic
psychopathy" as social isolation. Fifty years later, several standardizations of AS as a medical diagnosis were tentatively proposed, many of which diverge significantly from Asperger's original work.
Unlike what became known as AS, Asperger believed autistic
psychopathy could be found in people of all levels of intelligence,
including those with intellectual disability: as such, Asperger's
understanding of autistic pathology was more akin to what is known as
the autism spectrum today. Asperger defended the value of so-called "high-functioning" autistic
individuals, writing: "We are convinced, then, that autistic people have
their place in the organism of the social community. They fulfill their
role well, perhaps better than anyone else could, and we are talking of
people who as children had the greatest difficulties and caused untold
worries to their care-givers." Asperger also believed some would be capable of exceptional achievement and original thought later in life.
Asperger's paper was published during World War II and in German, so it was not widely read elsewhere. Lorna Wing used the term Asperger syndrome in 1976, and popularized it to the English-speaking medical community in her February 1981 publication of case studies of children showing the symptoms described by Asperger, and Uta Frith translated Asperger's paper to English in 1991. Sets of diagnostic criteria were outlined by Gillberg and Gillberg in 1989 and by Szatmari et al. in the same year. AS became a standard diagnosis when it was included in the tenth edition of the World Health Organization's diagnostic manual, International Classification of Diseases (ICD-10), published in 1990 and coming into effect in 1993; and in the fourth edition of the American Psychiatric Association's diagnostic reference, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), published in 1994.
Hundreds of books, articles, and websites later described AS and
prevalence estimates increased dramatically for ASD, with AS recognized
as an important subgroup. Whether AS should be seen as distinct from autism, particularly forms of autism sometimes described as "high functioning", became an issue receiving significant attention and disagreement, along with questions about the empirical validation of the DSM-IV and ICD-10 criteria.
With the publication of the next major editions of the DSM and ICD, the DSM-5 (published in 2013) and the ICD-11 (published in 2018, coming into effect in 2022), AS was eliminated as a separate diagnosis and folded into the autism spectrum. A scale of "severity" levels was included in the DSM-5, whereby most
people previously diagnosed with AS would have been classified as "level
1"; but these levels are widely opposed by the autistic community and are not included in the ICD-11. The ICD-11 characterizes ASD with qualifiers describing the presence of disorders of intellectual development and the degree of functional language impairment; the former diagnosis of Asperger syndrome is characterized as autism spectrum disorder without disorder of intellectual development and with mild or no impairment of functional language.
Students and families walk to support Autism Awareness Month.
People identifying with Asperger syndrome may refer to themselves in casual conversation as aspies (a term first used in print in the Boston Globe in 1998). Some autistic people have advocated a shift in perception of autism spectrum disorders as complex syndromes, neurodivergences, and/or neurominority cognitive styles rather than diseases that must be cured. Proponents of this neurodiversity paradigm reject the notion that there is an "ideal" brain configuration and that any deviation from the norm is pathological; they promote tolerance of neurodiversity. These views are the basis for the autistic rights and autistic pride movements, within the broader neurodiversity movement. There is a contrast between the attitude of people with AS, who
typically do not want to be cured and are proud of their identity; and
parents of children with AS, who more often seek a "cure" of their
children's autism.
Some researchers have argued that AS and other autism can be viewed as a different cognitive style, not a disorder, and that it should be removed from psychiatric and medical manuals classifying diseases (ICD) or mental disorders (DSM), much as homosexuality was removed.
Even some people typically associated with a pathology paradigm for autism are willing to consider AS a neutral difference. For example, in 2002, Simon Baron-Cohen
wrote of those with AS: "In the social world, there is no great benefit
to a precise eye for detail, but in the worlds of maths, computing,
cataloging, music, linguistics, engineering, and science, such an eye
for detail can lead to success rather than failure." Baron-Cohen cited
two reasons why it might still be useful to consider AS to be a
disability: to ensure provision for legally required special support,
and to recognize emotional difficulties from reduced empathy, which was
commonly associated with autism during that time but has since lost support. Baron-Cohen argues that the genes for ASD's combination of abilities have operated throughout recent human evolution and have made remarkable contributions to human history.
By contrast, Pier Jaarsma and Welin wrote in 2011 that the "broad
version of the neurodiversity claim, covering low-functioning as well
as high-functioning autism, is problematic. Only a narrow conception of neurodiversity, referring exclusively to high-functioning autists, is reasonable." They say that "higher functioning" individuals with autism may "not
[be] benefited with such a psychiatric defect-based diagnosis ... some
of them are being harmed by it, because of the disrespect the diagnosis
displays for their natural way of being", but "think that it is still
reasonable to include other categories of autism in the psychiatric
diagnostics. The narrow conception of the neurodiversity claim should be
accepted but the broader claim should not."
