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Wednesday, February 27, 2019

Zoopharmacognosy

From Wikipedia, the free encyclopedia

A cat eating grass - an example of zoopharmacognosy
 
Zoopharmacognosy is a behaviour in which non-human animals apparently self-medicate by selecting and ingesting or topically applying plants, soils, insects, and psychoactive drugs to prevent or reduce the harmful effects of pathogens and toxins. The term derives from Greek roots zoo ("animal"), pharmacon ("drug, medicine"), and gnosy ("knowing").

An example of zoopharmacognosy occurs when dogs eat grass to induce vomiting. However, the behaviour is more diverse than this. Animals ingest or apply non-foods such as clay, charcoal and even toxic plants and invertebrates, apparently to prevent parasitic infestation or poisoning.

Whether animals truly self-medicate remains a somewhat controversial subject because early evidence is mostly circumstantial or anecdotal, however, more recent examinations have adopted an experimental, hypothesis-driven approach. 

The methods by which animals self-medicate vary, but can be classified according to function as prophylactic (preventative, before infection or poisoning) or therapeutic (after infection, to combat the pathogen or poisoning). The behaviour is believed to have widespread adaptive significance.

History and etymology

In 1978, Janzen suggested that vertebrate herbivores might benefit medicinally from the secondary metabolites in their plant food.

In 1993, the term "zoopharmacognosy" was coined, derived from the Greek roots zoo ("animal"), pharma ("drug"), and gnosy ("knowing"). The term gained popularity from academic works and in a book by Cindy Engel entitled Wild Health: How Animals Keep Themselves Well and What We Can Learn from Them.

Mechanisms

The anti-parasitic effect of zoopharmacognosy could occur by at least two mechanisms. First, the ingested material may have pharmacological antiparasitic properties such that phytochemicals decrease the ability of worms to attach to the mucosal lining of the intestines, or chemotaxis attracts worms into the folds of leaves. Many ingested plants during purported zoopharmacognosy have a consistent physical property, e.g., the rough surface of the leaves sports many hooked and spiky hairs. So, parasites may became attached to the bristly surface or the coarse structure may function as a rasping plug, dislodging parasites from the intestines. The second possible mode of action is the material may initiate a purging response of the gastrointestinal tract by rapidly inducing diarrhea. This substantially decreases gut transit time, causes worm expulsion and interrupts the life cycle of parasites. This, or a similar, mechanism could explain undigested grass in the faeces of various animals such as birds, carnivores and primates.

Methods of self-medication

Some animals ingest or apply the substance when they appear to be well, suggesting the behaviour is preventative or prophylactic. In other cases, animals ingest or apply the substance when unwell, suggesting the behaviour is therapeutic or curative. There are three methods of self-medication, namely, ingestion, absorption, or topical application.

Ingestion

Many examples of zoopharmacognosy involve an animal ingesting a substance with (potential) medicinal properties.

Ants

Ants infected with Beauveria bassiana, a fungus, selectively consume harmful substances (reactive oxygen species, ROS) upon exposure to a fungal pathogen, yet avoid these in the absence of infection.

Mammals

A variety of simian species have been observed to medicate themselves when ill using materials such as plants.
 
A conceptual representation of how pre- and post-ingestive events control the manifestation of self-medicative behavior in mammalian herbivores.
 
Great apes often consume plants that have no nutritional values but which have beneficial effects on gut acidity or combat intestinal parasitic infection.

Chimpanzees sometimes select bitter leaves for chewing. Parasite infection drops noticeably after chimpanzees chew leaves of pith (Vernonia amyddalina), which have anti-parasitic activity against schistosoma, plasmodium and Leishmania. Chimpanzees don't consume this plant on a regular basis, but when they do eat it, it is often in small amounts by individuals that appear ill. Jane Goodall witnessed chimpanzees eating particular bushes, apparently to make themselves vomit. There are reports that chimpanzees swallow whole leaves of particular rough-leaved plants such as Aneilema aequinoctiale; these remove parasitic worms from their intestines.

Chimpanzees sometimes eat the leaves of the herbaceous Desmodium gangeticum. Undigested, non-chewed leaves were recovered in 4% of faecal samples of wild chimpanzees and clumps of sharp-edged grass leaves in 2%. The leaves have a rough surface or sharp-edges and the fact they were not chewed and excreted whole indicates they were not ingested for nutritional purposes. Furthermore, this leaf-swallowing was restricted to the rainy season when parasite re-infections are more common, and parasitic worms (Oesophagostomum stephanostomum) were found together with the leaves.

Chimpanzees, bonobos, and gorillas eat the fruits of Aframomum angustifolium. Laboratory assays of homogenized fruit and seed extracts show significant anti-microbial activity. Illustrating the medicinal knowledge of some species, apes have been observed selecting a particular part of a medicinal plant by taking off leaves and breaking the stem to suck out the juice.

Anubis baboons (Papio anubis) and hamadryas baboons (Papio hamadryas) in Ethiopia use fruits and leaves of Balanites aegyptiaca to control schistosomiasis. Its fruits contain diosgenin, a hormone precursor that presumably hinders the development of schistosomes.

African elephants (Loxodonta africana) apparently self-medicate to induce labour by chewing on the leaves of a particular tree from the family Boraginaceae; Kenyan women brew a tea from this tree for the same purpose.

White-nosed coatis (Nasua narica) in Panama take the menthol-scented resin from freshly scraped bark of Trattinnickia aspera (Burseraceae) and vigorously rub it into their own fur or that of other coatis, possibly to kill ectoparasites such as fleas, ticks, and lice, as well as biting insects such as mosquitoes; the resin contains triterpenes α - and β-amyrin, the eudesmane derivative β-selinene, and the sesquiterpene lactone 8β-hydroxyasterolide.

Domestic cats and dogs often select and ingest plant material, apparently to induce vomiting.

Indian wild boars selectively dig up and eat the roots of pigweed which humans use as an anthelmintic. Mexican folklore indicates that pigs eat pomegranate roots because they contain an alkaloid that is toxic to tapeworms.

A study on domestic sheep (Ovis aries) has provided clear experimental proof of self-medication via individual learning. Lambs in a treatment group were allowed to consume foods and toxins (grain, tannins, oxalic acid) that lead to malaise (negative internal states) and then allowed to eat a substance known to alleviate each malaise (sodium bentonite, polyethylene glycol and dicalcium phosphate, respectively). Control lambs ate the same foods and medicines, but this was disassociated temporally so they did not recuperate from the illness. After the conditioning, lambs were fed grain or food with tannins or oxalates and then allowed to choose the three medicines. The treatment animals preferred to eat the specific compound known to rectify the state of malaise induced by the food previously ingested. However, control animals did not change their pattern of use of the medicines, irrespective of the food consumed before the choice. Other ruminants learn to self-medicate against gastrointestinal parasites by increasing consumption of plant secondary compounds with antiparasitic actions.

Standard laboratory cages prevent mice from performing several natural behaviours for which they are highly motivated. As a consequence, laboratory mice sometimes develop abnormal behaviours indicative of emotional disorders such as depression and anxiety. To improve welfare, these cages are sometimes enriched with items such as nesting material, shelters and running wheels. Sherwin and Olsson tested whether such enrichment influenced the consumption of Midazolam, a drug widely used to treat anxiety in humans. Mice in standard cages, standard cages but with unpredictable husbandry, or enriched cages, were given a choice of drinking either non-drugged water or a solution of the Midazolam. Mice in the standard and unpredictable cages drank a greater proportion of the anxiolytic solution than mice from enriched cages, presumably because they had been experiencing greater anxiety. Early studies indicated that autoimmune (MRL/lpr) mice readily consume solutions with cyclophosphamide, an immunosuppressive drug that prevents inflammatory damage to internal organs. However, further studies provided contradictory evidence.
Geophagy
Many animals eat soil or clay, a behaviour known as geophagy. Clay is the primary ingredient of kaolin. It has been proposed that for primates, there are four hypotheses relating to geophagy in alleviating gastrointestinal disorders or upsets:
  • soils adsorb toxins such as phenolics and secondary metabolites
  • soil ingestion has an antacid action and adjusts the gut pH
  • soils act as an antidiarrhoeal agent
  • soils counteract the effects of endoparasites.
Furthermore, two hypotheses pertain to geophagy in supplementing minerals and elements:
  • soils supplement nutrient-poor diets
  • soils provide extra iron at high altitudes
Tapirs, forest elephants, colobus monkeys, mountain gorillas and chimpanzees seek out and eat clay, which absorbs intestinal bacteria and their toxins and alleviates stomach upset and diarrhoea. Cattle eat clay-rich termite mound soil, which deactivates ingested pathogens or fruit toxins.

Birds

Parrots eating earth
 
Many parrot species in the Americas, Africa, and Papua New Guinea consume kaolin or clay, which both releases minerals and absorbs toxic compounds from the gut. Great bustards eat blister beetles of the genus Meloe to decrease parasite load in the digestive system; cantharidin, the toxic compound in blister beetles, can kill a great bustard if too many beetles are ingested. Great bustards may eat toxic blister beetles of the genus Meloe to increase the sexual arousal of males.

Invertebrates

Woolly bear caterpillars (Grammia incorrupta) are sometimes lethally endoparasitised by tachinid flies. The caterpillars ingest plant toxins called pyrrolizidine alkaloids, which improve the survival of by conferring resistance against the flies. Crucially, parasitised caterpillars are more likely than non-parasitised caterpillars to specifically ingest large amounts of pyrrolizidine alkaloids, and excessive ingestion of these toxins reduces the survival of non-parasitised caterpillars. These three findings are all consistent with the adaptive plasticity theory.

The tobacco hornworm ingests nicotine which reduces colony growth and toxicity of Bacillus thuringiensis, leading to increased survival of the hornworm.

Absorption and adsorption

The swallowing of whole leaves by apes without chewing has been observed for over 40 plant species. 

Wild chimpanzees sometimes seek whole leaves of the Aspilia plant. These contain thiarubrine-A, a chemical active against intestinal nematode parasites, however, it is quickly broken-down by the stomach. The chimpanzees pick the Aspilia leaves and, rather than chewing them, they roll them around in their mouths, sometimes for as long as 25 seconds. They then swallow the capsule-like leaves whole. As many as 15 to 35 Aspilia leaves may be used in each bout of this behaviour, particularly in the rainy season when there are many parasitic larvae leading to an increased risk of infection.

Bonobos sometimes swallow non-chewed stem-strips of (Manniophyton fulvum). Despite the plant being abundantly available all year, M. fulvum is ingested only at specific times, in small amounts, and by a small proportion of bonobos in each group.

Topical application

Some animals apply substances with medicinal properties to their skin. Again, this can be prophylactic or curative. In some cases, this is known as self-anointing.

Mammals

A female capuchin monkey in captivity was observed using tools covered in a sugar-based syrup to groom her wounds and those of her infant.

North American brown bears (Ursos arctos) make a paste of Osha roots (Ligusticum porteri) and saliva and rub it through their fur to repel insects or soothe bites. This plant, locally known as "bear root", contains 105 active compounds, such as coumarins that may repel insects when topically applied. Navajo Indians are said to have learned to use this root medicinally from the bear for treating stomach aches and infections.

A range of primates rub millipedes onto their fur and skin; millipedes contain benzoquinones, compounds known to be potently repellent to insects.

Tufted capuchins (Cebus apella) rub various parts of their body with carpenter ants (Camponotus rufipes) or allow the ants to crawl over them, in a behaviour called anting. The capuchins often combine anting with urinating into their hands and mixing the ants with the urine.

Birds

More than 200 species of song birds wipe ants, a behaviour known as anting. Birds either grasp ants in their bill and wipe them vigorously along the spine of each feather down to the base, or sometimes roll in ant hills twisting and turning so the ants crawl through their feathers. Birds most commonly use ants that spray formic acid. In laboratory tests, this acid is harmful to feather lice. Its vapour alone can kill them. 

Some birds select nesting material rich in anti-microbial agents that may protect themselves and their young from harmful infestations or infections. European starlings (Sturnus vulgaris) preferentially select and line their nests with wild carrot (Daucus carota); chicks from nests lined with this have greater levels of haemoglobin compared to those from nests which are not, although there is no difference in the weight or feather development of the chicks. Laboratory studies show that wild carrot substantially reduces the emergence of the instars of mites. House sparrows (Passer domesticus) have been observed to line their nests with materials from the neem tree (Azadirachta indica) but change to quinine-rich leaves of the Krishnachua tree (Caesalpinia pulcherrima) during an outbreak of malaria; quinine controls the symptoms of malaria.

Social zoopharmacognosy

Wood ants incorporate resin into their nest to inhibit the growth of microorganisms
 
Zoopharmacognosy is not always exhibited in a way that benefits the individual. Sometimes the target of the medication is the group or the colony. 

Wood ants (Formica paralugubris) often incorporate large quantities of solidified conifer resin into their nests. Laboratory studies have shown this resin inhibits the growth of bacteria and fungi in a context mimicking natural conditions. The ants show a strong preference for resin over twigs and stones, which are building materials commonly available in their environment. There is seasonal variation in the foraging of ants: the preference for resin over twigs is more pronounced in spring than in summer, whereas in autumn the ants collect twigs and resin at equal rates. The relative collection rate of resin versus stones does not depend on infection with the entomopathogenic fungus Metarhizium anisopliae in laboratory conditions, indicating the resin collection is prophylactic rather than therapeutic.

Honey bees also incorporate plant-produced resins into their nest architecture, which can reduce chronic elevation of an individual bee's immune response. When colonies of honey bees are challenged with the fungal parasite (Ascophaera apis), the bees increase their resin foraging. Additionally, colonies experimentally enriched with resin have decreased infection intensities of the fungus.

Transgenerational zoopharmacognosy

Adult monarch butterflies lay their eggs on toxic plants to reduce parasite growth and disease in their offspring
 
Zoopharmacognosy can be classified depending on the target of the medication. Some animals lay their eggs in such a way that their offspring are the target of the medication. 

Adult monarch butterflies preferentially lay their eggs on toxic plants such as milkweed which reduce parasite growth and disease in their offspring caterpillars. This has been termed transgenerational therapeutic medication.

When fruit flies detect the presence of parasitoid wasps, they preferentially lay their eggs in high-ethanol food; this reduces infection risk in their offspring. This has been termed transgenerational prophylaxis.

Value to humans

In an interview with Neil Campbell, Rodriguez describes the importance of biodiversity to medicine:
Some of the compounds we've identified by zoopharmacognosy kill parasitic worms, and some of these chemicals may be useful against tumors. There is no question that the templates for most drugs are in the natural world.

Media

  • 2002 British documentary television series Weird Nature episode 6 Peculiar Potions documents variety of animals engaging in intoxication or zoopharmacognosy.

Self-medication

From Wikipedia, the free encyclopedia

Self-medication is a human behavior in which an individual uses a substance or any exogenous influence to self-administer treatment for physical or psychological ailments.

The most widely self-medicated substances are over-the-counter drugs used to treat common health issues at home, as well as dietary supplements. These do not require a doctor's prescription to obtain and, in some countries, are available in supermarkets and convenience stores.

The psychology of self-medicating with psychoactive drugs is typically within the specific context of using recreational drugs, alcohol, comfort food, and other forms of behavior to alleviate symptoms of mental distress, stress and anxiety, including mental illnesses and/or psychological trauma, is particularly unique and can serve as a serious detriment to physical and mental health if motivated by addictive mechanisms. In postsecondary (university/college) students, the use of self-medicating of study-drugs such as Adderall, Ritalin, and Concerta has been widely reported and discussed in literature.

Products are marketed by manufacturers as useful for self-medication, sometimes on the basis of questionable evidence. Claims that nicotine has medicinal value have been used to market cigarettes as self-administered medicines. These claims have been criticized as inaccurate by independent researchers. Unverified and unregulated third-party health claims are used to market dietary supplements.

Self-medication is often seen as gaining personal independence from established medicine, and it can be seen as a human right, implicit in, or closely related to the right to refuse professional medical treatment. Self-medication can cause unintentional self-harm.

Definition

Generally speaking, self-medication is defined as "the use of drugs to treat self-diagnosed disorders or symptoms, or the intermittent or continued use of a prescribed drug for chronic or recurrent disease or symptoms"

Psychology and psychiatry

Self-medication hypothesis

As different drugs have different effects, they may be used for different reasons. According to the self-medication hypothesis (SMH), the individuals' choice of a particular drug is not accidental or coincidental, but instead, a result of the individuals' psychological condition, as the drug of choice provides relief to the user specific to his or her condition. Specifically, addiction is hypothesized to function as a compensatory means to modulate effects and treat distressful psychological states, whereby individuals choose the drug that will most appropriately manage their specific type of psychiatric distress and help them achieve emotional stability.

The self-medication hypothesis (SMH) originated in papers by Edward Khantzian, Mack and Schatzberg, David F. Duncan, and a response to Khantzian by Duncan. The SMH initially focused on heroin use, but a follow-up paper added cocaine. The SMH was later expanded to include alcohol, and finally all drugs of addiction.

According to Khantzian's view of addiction, drug users compensate for deficient ego function by using a drug as an "ego solvent", which acts on parts of the self that are cut off from consciousness by defense mechanisms. According to Khantzian, drug dependent individuals generally experience more psychiatric distress than non-drug dependent individuals, and the development of drug dependence involves the gradual incorporation of the drug effects and the need to sustain these effects into the defensive structure-building activity of the ego itself. The addict's choice of drug is a result of the interaction between the psychopharmacologic properties of the drug and the affective states from which the addict was seeking relief. The drug's effects substitute for defective or non-existent ego mechanisms of defense. The addict's drug of choice, therefore, is not random. 

While Khantzian takes a psychodynamic approach to self-medication, Duncan's model focuses on behavioral factors. Duncan described the nature of positive reinforcement (e.g., the "high feeling", approval from peers), negative reinforcement (e.g. reduction of negative affect) and avoidance of withdrawal symptoms, all of which are seen in those who develop problematic drug use, but are not all found in all recreational drug users. While earlier behavioral formulations of drug dependence using operant conditioning maintained that positive and negative reinforcement were necessary for drug dependence, Duncan maintained that drug dependence was not maintained by positive reinforcement, but rather by negative reinforcement. Duncan applied a public health model to drug dependence, where the agent (the drug of choice) infects the host (the drug user) through a vector (e.g., peers), while the environment supports the disease process, through stressors and lack of support.

Khantzian revisited the SMH, suggesting there is more evidence that psychiatric symptoms, rather than personality styles, lie at the heart of drug use disorders. Khantzian specified that the two crucial aspects of the SMH were that (1) drugs of abuse produce a relief from psychological suffering and (2) the individual's preference for a particular drug is based on its psychopharmacological properties. The individual's drug of choice is determined through experimentation, whereby the interaction of the main effects of the drug, the individual's inner psychological turmoil, and underlying personality traits identify the drug that produces the desired effects.

Meanwhile, Duncan's work focuses on the difference between recreational and problematic drug use. Data obtained in the Epidemiologic Catchment Area Study demonstrated that only 20% of drug users ever experience an episode of drug abuse (Anthony & Helzer, 1991), while data obtained from the National Comorbidity Study demonstrated that only 15% of alcohol users and 15% of illicit drug users ever become dependent. A crucial determinant of whether a drug user develops drug abuse is the presence or absence of negative reinforcement, which is experienced by problematic users, but not by recreational users. According to Duncan, drug dependence is an avoidance behavior, where an individual finds a drug that produces a temporary escape from a problem, and taking the drug is reinforced as an operant behavior.

Specific mechanisms

Some mental illness sufferers attempt to correct their illnesses by use of certain drugs. Depression is often self-medicated with alcohol, tobacco, cannabis, or other mind-altering drug use. While this may provide immediate relief of some symptoms such as anxiety, it may evoke and/or exacerbate some symptoms of several kinds of mental illnesses that are already latently present, and may lead to addiction/dependence, among other side effects of long-term use of the drug. 

Sufferers of posttraumatic stress disorder have been known to self-medicate, as well as many individuals without this diagnosis who have suffered from (mental) trauma.

Due to the different effects of the different classes of drugs, the SMH postulates that the appeal of a specific class of drugs differs from person to person. In fact, some drugs may be aversive for individuals for whom the effects could worsen affective deficits.

CNS depressants

Alcohol and sedative/hypnotic drugs, such as barbiturates and benzodiazepines, are central nervous system (CNS) depressants that lower inhibitions via anxiolysis. Depressants produce feelings of relaxation and sedation, while relieving feelings of depression and anxiety. Though they are generally ineffective antidepressants, as most are short-acting, the rapid onset of alcohol and sedative/hypnotics softens rigid defenses and, in low to moderate doses, provides relief from depressive affect and anxiety. As alcohol also lowers inhibitions, alcohol is also hypothesized to be used by those who normally constrain emotions by attenuating intense emotions in high or obliterating doses, which allows them to express feelings of affection, aggression and closeness. People with social anxiety disorder commonly use these drugs to overcome their highly set inhibitions.

Psychostimulants

Psychostimulants, such as cocaine, amphetamines, methylphenidate, caffeine, and nicotine, produce improvements in physical and mental functioning, including increased energy and feelings of euphoria. Stimulants tend to be used by individuals who experience depression, to reduce anhedonia and increase self-esteem. The SMH also hypothesizes that hyperactive and hypomanic individuals use stimulants to maintain their restlessness and heighten euphoria. Additionally, stimulants are useful to individuals with social anxiety by helping individuals break through their inhibitions. Some reviews suggest that students use psychostimulants recreationally to medicate for underlying deeper issues, such as depression or anxiety, and that their chance of self-medicating of these drugs can be loosely predicted using a variety of risk factors including childhood parental monitoring, participating in a sports team, or through the DAST-10 (screening test).

Opiates

Opiates, such as heroin and morphine, function as an analgesic by binding to opioid receptors in the brain and gastrointestinal tract. This binding reduces the perception of and reaction to pain, while also increasing pain tolerance. Opiates are hypothesized to be used as self-medication for aggression and rage. Opiates are effective anxiolytics, mood stabilizers, and anti-depressants, however, people tend to self-medicate anxiety and depression with depressants and stimulants respectively, though this is by no means an absolute analysis.

Cannabis

Cannabis is paradoxical in that it simultaneously produces stimulating, sedating and mildly psychedelic properties and both anxiolytic or anxiogenic properties, depending on the individual and circumstances of use. Depressant properties are more obvious in occasional users, and stimulating properties are more common in chronic users. Khantzian noted that research had not sufficiently addressed a theoretical mechanism for cannabis, and therefore did not include it in the SMH.

Effectiveness

Self-medicating excessively for prolonged periods of time with benzodiazepines or alcohol often makes the symptoms of anxiety or depression worse. This is believed to occur as a result of the changes in brain chemistry from long-term use. Of those who seek help from mental health services for conditions including anxiety disorders such as panic disorder or social phobia, approximately half have alcohol or benzodiazepine dependence issues.

Sometimes anxiety precedes alcohol or benzodiazepine dependence but the alcohol or benzodiazepine dependence acts to keep the anxiety disorders going, often progressively making them worse. However, some people addicted to alcohol or benzodiazepines, when it is explained to them that they have a choice between ongoing poor mental health or quitting and recovering from their symptoms, decide on quitting alcohol or benzodiazepines or both. It has been noted that every individual has an individual sensitivity level to alcohol or sedative hypnotic drugs, and what one person can tolerate without ill health, may cause another to suffer very ill health, and even moderate drinking can cause rebound anxiety syndrome and sleep disorders. A person suffering the toxic effects of alcohol will not benefit from other therapies or medications, as these do not address the root cause of the symptoms.

Nicotine addiction seems to worsen mental health problems. Nicotine withdrawal depresses mood, increases anxiety and stress, and disrupts sleep. Although nicotine products temporarily relieve there nicotine withdrawal symptoms, an addiction causes stress and mood to be worse on average, due to mild withdrawal symptoms between hits. Nicotine addicts need the nicotine to temporarily feel normal. Nicotine industry marketing has claimed that nicotine is both less harmful and therapeutic for people with mental illness, and is a form of self-medication. This claim has been criticised by independent researchers.

Self medicating is a very common precursor to full addictions and the habitual use of any addictive drug has been demonstrated to greatly increase the risk of addiction to additional substances due to long-term neuronal changes. Addiction to any/every drug of abuse tested so far has been correlated with an enduring reduction in the expression of GLT1 (EAAT2) in the nucleus accumbens and is implicated in the drug-seeking behavior expressed nearly universally across all documented addiction syndromes. This long-term dysregulation of glutamate transmission is associated with an increase in vulnerability to both relapse-events after re-exposure to drug-use triggers as well as an overall increase in the likelihood of developing addiction to other reinforcing drugs. Drugs which help to re-stabilize the glutamate system such as N-acetylcysteine have been proposed for the treatment of addiction to cocaine, nicotine, and alcohol.

Infectious disease

Self-medication with antibiotics is commonplace in some countries, such as Greece. Such use is cited as a potential factor in the incidence of certain antibiotic resistant bacterial infections in places like Nigeria.

In a questionnaire designed to evaluate self-medication rates amongst the population of Khartoum, Sudan, 48.1% of respondents reported self-medicating with antibiotics within the past 30 days, 43.4% reported self-medicating with antimalarials, and 17.5% reported self-medicating with both. Overall, the total prevalence of reported self-medication with one or both classes of anti-infective agents within the past month was 73.9%. Furthermore, according to the associated study, data indicated that self-medication "varies significantly with a number of socio-economic characteristics" and the "main reason that was indicated for the self-medication was financial constraints".

Similarly, in a survey of university students in Southern China, 47.8% of respondents reported self-medicating with antibiotics.

Physicians and medical students

In a survey of West Bengal, India undergraduate medical school students, 57% reported self-medicating. The type of drugs most frequently used for self-medication were antibiotics (31%), analgesics (23%), antipyretics (18%), antiulcerics (9%), cough suppressants (8%), multivitamins (6%), and anthelmintics (4%).

Another study indicated that 53% of physicians in Karnataka, India reported self-administration of antibiotics.

Children

A study of Luo children in western Kenya found that 19% reported engaging in self-treatment with either herbal or pharmaceutical medicine. Proportionally, boys were much more likely to self-medicate using conventional medicine than herbal medicine as compared with girls, a phenomenon which was theorized to be influenced by their relative earning potential.

Regulation

Self-medication is highly regulated in much of the world and many classes of drugs are available for administration only upon prescription by licensed medical personnel. Safety, social order, commercialization, and religion have historically been among the prevailing factors that lead to such prohibition.

Tobacco smoking

From Wikipedia, the free encyclopedia

Marlboro's package of the ice blast cigarette

Tobacco smoking is the practice of smoking tobacco and inhaling tobacco smoke (consisting of particle and gaseous phases). (A more broad definition may include simply taking tobacco smoke into the mouth, and then releasing it, as is done by some with tobacco pipes and cigars.) The practice is believed to have begun as early as 5000–3000 BC in Mesoamerica and South America. Tobacco was introduced to Eurasia in the late 17th century by European colonists, where it followed common trade routes. The practice encountered criticism from its first import into the Western world onwards but embedded itself in certain strata of a number of societies before becoming widespread upon the introduction of automated cigarette-rolling apparatus.

German scientists identified a link between smoking and lung cancer in the late 1920s, leading to the first anti-smoking campaign in modern history, albeit one truncated by the collapse of Nazi Germany at the end of World War II. In 1950, British researchers demonstrated a clear relationship between smoking and cancer. Evidence continued to mount in the 1980s, which prompted political action against the practice. Rates of consumption since 1965 in the developed world have either peaked or declined. However, they continue to climb in the developing world.

Smoking is the most common method of consuming tobacco, and tobacco is the most common substance smoked. The agricultural product is often mixed with additives and then combusted. The resulting smoke is then inhaled and the active substances absorbed through the alveoli in the lungs or the oral mucosa. Combustion was traditionally enhanced by addition of potassium or nitrates. Many substances in cigarette smoke trigger chemical reactions in nerve endings, which heighten heart rate, alertness and reaction time, among other things. Dopamine and endorphins are released, which are often associated with pleasure. As of 2008 to 2010, tobacco is used by about 49% of men and 11% of women aged 15 or older in fourteen low-income and middle-income countries (Bangladesh, Brazil, China, Egypt, India, Mexico, Philippines, Poland, Russia, Thailand, Turkey, Ukraine, Uruguay and Vietnam), with about 80% of this usage in the form of smoking. The gender gap tends to be less pronounced in lower age groups.

Many smokers begin during adolescence or early adulthood. During the early stages, a combination of perceived pleasure acting as positive reinforcement and desire to respond to social peer pressure may offset the unpleasant symptoms of initial use, which typically include nausea and coughing. After an individual has smoked for some years, the avoidance of withdrawal symptoms and negative reinforcement become the key motivations to continue. 

A study of first smoking experiences of seventh-grade students found out that the most common factor leading students to smoke is cigarette advertisements. Smoking by parents, siblings and friends also encourages students to smoke.

History

Use in ancient cultures

Aztec women are handed flowers and smoking tubes before eating at a banquet, Florentine Codex, 16th century.
 
Smoking's history dates back to as early as 5000–3000 BC, when the agricultural product began to be cultivated in Mesoamerica and South America; consumption later evolved into burning the plant substance either by accident or with intent of exploring other means of consumption. The practice worked its way into shamanistic rituals. Many ancient civilizations – such as the Babylonians, the Indians, and the Chinese – burnt incense during religious rituals. Smoking in the Americas probably had its origins in the incense-burning ceremonies of shamans but was later adopted for pleasure or as a social tool. The smoking of tobacco and various hallucinogenic drugs was used to achieve trances and to come into contact with the spirit world. 

Eastern North American tribes would carry large amounts of tobacco in pouches as a readily accepted trade item and would often smoke it in ceremonial pipes, either in sacred ceremonies or to seal bargains. Adults as well as children enjoyed the practice. It was believed that tobacco was a gift from the Creator and that the exhaled tobacco smoke was capable of carrying one's thoughts and prayers to heaven.

Apart from smoking, tobacco had a number of uses as medicine. As a pain killer it was used for earache and toothache and occasionally as a poultice. Smoking was said by the desert Indians to be a cure for colds, especially if the tobacco was mixed with the leaves of the small Desert sage, Salvia dorrii, or the root of Indian balsam or cough root, Leptotaenia multifida, the addition of which was thought to be particularly good for asthma and tuberculosis.

Popularization

Gentlemen Smoking and Playing Backgammon in an Interior by Dirck Hals, 1627.
 
In 1612, six years after the settlement of Jamestown, Virginia, John Rolfe was credited as the first settler to successfully raise tobacco as a cash crop. The demand quickly grew as tobacco, referred to as "brown gold", revived the Virginia joint stock company from its failed gold expeditions. In order to meet demands from the Old World, tobacco was grown in succession, quickly depleting the soil. This became a motivator to settle west into the unknown continent, and likewise an expansion of tobacco production. Indentured servitude became the primary labor force up until Bacon's Rebellion, from which the focus turned to slavery. This trend abated following the American Revolution as slavery became regarded as unprofitable. However, the practice was revived in 1794 with the invention of the cotton gin.

Frenchman Jean Nicot (from whose name the word nicotine is derived) introduced tobacco to France in 1560, and tobacco then spread to England. The first report of a smoking Englishman is of a sailor in Bristol in 1556, seen "emitting smoke from his nostrils". Like tea, coffee and opium, tobacco was just one of many intoxicants that was originally used as a form of medicine. Tobacco was introduced around 1600 by French merchants in what today is modern-day Gambia and Senegal. At the same time, caravans from Morocco brought tobacco to the areas around Timbuktu, and the Portuguese brought the commodity (and the plant) to southern Africa, establishing the popularity of tobacco throughout all of Africa by the 1650s. 

Soon after its introduction to the Old World, tobacco came under frequent criticism from state and religious leaders. James VI and I, King of Scotland and England, produced the treatise A Counterblaste to Tobacco in 1604, and also introduced excise duty on the product. Murad IV, sultan of the Ottoman Empire 1623–40 was among the first to attempt a smoking ban by claiming it was a threat to public morals and health. The Chongzhen Emperor of China issued an edict banning smoking two years before his death and the overthrow of the Ming dynasty. Later, the Manchu rulers of the Qing dynasty, would proclaim smoking "a more heinous crime than that even of neglecting archery". In Edo period Japan, some of the earliest tobacco plantations were scorned by the shogunate as being a threat to the military economy by letting valuable farmland go to waste for the use of a recreational drug instead of being used to plant food crops.

Bonsack's cigarette rolling machine, as shown on U.S. patent 238,640.
 
Religious leaders have often been prominent among those who considered smoking immoral or outright blasphemous. In 1634, the Patriarch of Moscow forbade the sale of tobacco, and sentenced men and women who flouted the ban to have their nostrils slit and their backs flayed. Pope Urban VIII likewise condemned smoking on holy places in a papal bull of 1624. Despite some concerted efforts, restrictions and bans were largely ignored. When James I of England, a staunch anti-smoker and the author of A Counterblaste to Tobacco, tried to curb the new trend by enforcing a 4000% tax increase on tobacco in 1604 it was unsuccessful, as suggested by the presence of around 7,000 tobacco outlets in London by the early 17th century. From this point on for some centuries, several administrations withdrew from efforts at discouragement and instead turned tobacco trade and cultivation into sometimes lucrative government monopolies.

By the mid-17th century most major civilizations had been introduced to tobacco smoking and in many cases had already assimilated it into the native culture, despite some continued attempts upon the parts of rulers to eliminate the practice with penalties or fines. Tobacco, both product and plant, followed the major trade routes to major ports and markets, and then on into the hinterlands. The English language term smoking appears to have entered currency in the late 18th century, before which less abbreviated descriptions of the practice such as drinking smoke were also in use.

Growth in the US remained stable until the American Civil War in 1860s, when the primary agricultural workforce shifted from slavery to sharecropping. This, along with a change in demand, accompanied the industrialization of cigarette production as craftsman James Bonsack created a machine in 1881 to partially automate their manufacture.

Social attitudes and public health

Newsies smoking at Skeeter's Branch, St. Louis, MO. Photograph by Lewis Hine, 1910
 
In Germany, anti-smoking groups, often associated with anti-liquor groups, first published advocacy against the consumption of tobacco in the journal Der Tabakgegner (The Tobacco Opponent) in 1912 and 1932. In 1929, Fritz Lickint of Dresden, Germany, published a paper containing formal statistical evidence of a lung cancer–tobacco link. During the Great Depression Adolf Hitler condemned his earlier smoking habit as a waste of money, and later with stronger assertions. This movement was further strengthened with Nazi reproductive policy as women who smoked were viewed as unsuitable to be wives and mothers in a German family.

The anti-tobacco movement in Nazi Germany did not reach across enemy lines during the Second World War, as anti-smoking groups quickly lost popular support. By the end of the Second World War, American cigarette manufacturers quickly reentered the German black market. Illegal smuggling of tobacco became prevalent, and leaders of the Nazi anti-smoking campaign were silenced. As part of the Marshall Plan, the United States shipped free tobacco to Germany; with 24,000 tons in 1948 and 69,000 tons in 1949. Per capita yearly cigarette consumption in post-war Germany steadily rose from 460 in 1950 to 1,523 in 1963. By the end of the 20th century, anti-smoking campaigns in Germany were unable to exceed the effectiveness of the Nazi-era climax in the years 1939–41 and German tobacco health research was described by Robert N. Proctor as "muted".

A lengthy study conducted in order to establish the strong association necessary for legislative action (US cigarette consumption per person blue, male lung cancer rate green)
 
In 1950, Richard Doll published research in the British Medical Journal showing a close link between smoking and lung cancer. Beginning in December 1952, the magazine Reader's Digest published "Cancer by the Carton", a series of articles that linked smoking with lung cancer.

In 1954, the British Doctors Study, a prospective study of some 40 thousand doctors for about 2.5 years, confirmed the suggestion, based on which the government issued advice that smoking and lung cancer rates were related. In January 1964, the United States Surgeon General's Report on Smoking and Health likewise began suggesting the relationship between smoking and cancer.

As scientific evidence mounted in the 1980s, tobacco companies claimed contributory negligence as the adverse health effects were previously unknown or lacked substantial credibility. Health authorities sided with these claims up until 1998, from which they reversed their position. The Tobacco Master Settlement Agreement, originally between the four largest US tobacco companies and the Attorneys General of 46 states, restricted certain types of tobacco advertisement and required payments for health compensation; which later amounted to the largest civil settlement in United States history.

Social campaigns have been instituted in many places to discourage smoking, such as Canada's National Non-Smoking Week

From 1965 to 2006, rates of smoking in the United States declined from 42% to 20.8%. The majority of those who quit were professional, affluent men. Although the per-capita number of smokers decreased, the average number of cigarettes consumed per person per day increased from 22 in 1954 to 30 in 1978. This paradoxical event suggests that those who quit smoked less, while those who continued to smoke moved to smoke more light cigarettes. The trend has been paralleled by many industrialized nations as rates have either leveled-off or declined. In the developing world, however, tobacco consumption continues to rise at 3.4% in 2002. In Africa, smoking is in most areas considered to be modern, and many of the strong adverse opinions that prevail in the West receive much less attention. Today Russia leads as the top consumer of tobacco followed by Indonesia, Laos, Ukraine, Belarus, Greece, Jordan, and China.

Consumption

Methods

Tobacco is an agricultural product processed from the fresh leaves of plants in the genus Nicotiana. The genus contains a number of species, however, Nicotiana tabacum is the most commonly grown. Nicotiana rustica follows as second containing higher concentrations of nicotine. These leaves are harvested and cured to allow for the slow oxidation and degradation of carotenoids in tobacco leaf. This produces certain compounds in the tobacco leaves which can be attributed to sweet hay, tea, rose oil, or fruity aromatic flavors. Before packaging, the tobacco is often combined with other additives in order to enhance the addictive potency, shift the products pH, or improve the effects of smoke by making it more palatable. In the United States these additives are regulated to 599 substances. The product is then processed, packaged, and shipped to consumer markets. 

Field of tobacco organized in rows extending to the horizon.
Tobacco field in Intercourse, Pennsylvania.
 
Powderly stripps hung vertically, slightly sun bleached.
Basma leaves curing in the sun at Pomak village of Xanthi, Thrace, Greece.
 
Rectangular strips stacked in an open square box.
Processed tobacco pressed into flakes for pipe smoking.
Beedi
Beedis are thin South Asian cigarettes filled with tobacco flakes and wrapped in a tendu leaf tied with a string at one end. They produce higher levels of carbon monoxide, nicotine, and tar than cigarettes typical in the United States.
Tendu Patta (Leaf) Collection for Beedi industries
Cigars
Cigars are tightly rolled bundles of dried and fermented tobacco which are ignited so that smoke may be drawn into the smoker's mouth. They are generally not inhaled because of the high alkalinity of the smoke, which can quickly become irritating to the trachea and lungs. The prevalence of cigar smoking varies depending on location, historical period, and population surveyed, and prevalence estimates vary somewhat depending on the survey method. The United States is the top consuming country by far, followed by Germany and the United Kingdom; the US and Western Europe account for about 75% of cigar sales worldwide. As of 2005 it is estimated that 4.3% of men and 0.3% of women smoke cigars in the USA.
Cigarettes
Cigarettes, French for "small cigar", are a product consumed through smoking and manufactured out of cured and finely cut tobacco leaves and reconstituted tobacco, often combined with other additives, which are then rolled or stuffed into a paper-wrapped cylinder. Cigarettes are ignited and inhaled, usually through a cellulose acetate filter, into the mouth and lungs.
Hookah
Hookah are a single or multi-stemmed (often glass-based) water pipe for smoking. Originally from India. The hookah was a symbol of pride and honor for the landlords, kings and other such high class people. Now, the hookah has gained immense popularity, especially in the Middle East. A hookah operates by water filtration and indirect heat. It can be used for smoking herbal fruits, tobacco, or cannabis.
 
Kretek
Kretek are cigarettes made with a complex blend of tobacco, cloves and a flavoring "sauce". It was first introduced in the 1880s in Kudus, Java, to deliver the medicinal eugenol of cloves to the lungs. The quality and variety of tobacco play an important role in kretek production, from which kretek can contain more than 30 types of tobacco. Minced dried clove buds weighing about one-third of the tobacco blend are added to add flavoring. In 2004 the United States prohibited cigarettes from having a "characterizing flavor" of certain ingredients other than tobacco and menthol, thereby removing kretek from being classified as cigarettes.
 
Passive smoking
Passive smoking is the usually involuntary consumption of smoked tobacco. Second-hand smoke (SHS) is the consumption where the burning end is present, environmental tobacco smoke (ETS) or third-hand smoke is the consumption of the smoke that remains after the burning end has been extinguished. Because of its negative implications, this form of consumption has played a central role in the regulation of tobacco products.
 
Pipe smoking
Pipe smoking typically consists of a small chamber (the bowl) for the combustion of the tobacco to be smoked and a thin stem (shank) that ends in a mouthpiece (the bit). Shredded pieces of tobacco are placed into the chamber and ignited.
 
Roll-your-own
Roll-your-own or hand-rolled cigarettes, often called "rollies", "cigi" or "Roll-ups", are very popular particularly in European countries and the UK. These are prepared from loose tobacco, cigarette papers, and filters all bought separately. They are usually much cheaper than ready-made cigarettes and small contraptions can be bought making the process easier.
 
Vaporizer
A vaporizer is a device used to sublimate the active ingredients of plant material. Rather than burning the herb, which produces potentially irritating, toxic, or carcinogenic by-products; a vaporizer heats the material in a partial vacuum so that the active compounds contained in the plant boil off into a vapor. This method is often preferable when medically administrating the smoke substance, as opposed to directly pyrolyzing the plant material.

Physiology

A graph that shows the efficiency of smoking as a way to absorb nicotine compared to other forms of intake.
 
The active substances in tobacco, especially cigarettes, are administered by burning the leaves and inhaling the vaporized gas that results. This quickly and effectively delivers substances into the bloodstream by absorption through the alveoli in the lungs. The lungs contain some 300 million alveoli, which amounts to a surface area of over 70 m2 (about the size of a tennis court). This method is not completely efficient as not all of the smoke will be inhaled, and some amount of the active substances will be lost in the process of combustion, pyrolysis. Pipe and Cigar smoke are not inhaled because of its high alkalinity, which are irritating to the trachea and lungs. However, because of its higher alkalinity (pH 8.5) compared to cigarette smoke (pH 5.3), non-ionized nicotine is more readily absorbed through the mucous membranes in the mouth. Nicotine absorption from cigar and pipe, however, is much less than that from cigarette smoke. Nicotine and cocaine activate similar patterns of neurons, which supports the existence of common substrates among these drugs.

The inhaled nicotine mimics nicotinic acetylcholine which when bound to nicotinic acetylcholine receptors prevents the reuptake of acetylcholine thereby increasing that neurotransmitter in those areas of the body. These nicotinic acetylcholine receptors are located in the central nervous system and at the nerve-muscle junction of skeletal muscles; whose activity increases heart rate, alertness, and faster reaction times. Nicotine acetylcholine stimulation is not directly addictive. However, since dopamine-releasing neurons are abundant on nicotine receptors, dopamine is released; and, in the nucleus accumbens, dopamine is associated with motivation causing reinforcing behavior. Dopamine increase, in the prefrontal cortex, may also increase working memory.

When tobacco is smoked, most of the nicotine is pyrolyzed. However, a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. There is also a formation of harmane (a MAO inhibitor) from the acetaldehyde in tobacco smoke. This may play a role in nicotine addiction, by facilitating a dopamine release in the nucleus accumbens as a response to nicotine stimuli. Using rat studies, withdrawal after repeated exposure to nicotine results in less responsive nucleus accumbens cells, which produce dopamine responsible for reinforcement.

Demographics

Percentage of females smoking any tobacco product
 
Percentage of males smoking any tobacco product. Note that there is a difference between the scales used for females and the scales used for males.
 
As of 2000, smoking was practiced by around 1.22 billion people. At current rates of 'smoker replacement' and market growth, this may reach around 1.9 billion in 2025.

Smoking may be up to five times more prevalent among men than women in some communities, although the gender gap usually declines with younger age. In some developed countries smoking rates for men have peaked and begun to decline, while for women they continue to climb.

As of 2002, about twenty percent of young teenagers (13–15) smoked worldwide. 80,000 to 100,000 children begin smoking every day, roughly half of whom live in Asia. Half of those who begin smoking in adolescent years are projected to go on to smoke for 15 to 20 years.

The World Health Organization (WHO) states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional economies. Rates of smoking have leveled off or declined in the developed world. In the developing world, however, tobacco consumption is rising by 3.4% per year as of 2002.

The WHO in 2004 projected 58.8 million deaths to occur globally, from which 5.4 million are tobacco-attributed, and 4.9 million as of 2007. As of 2002, 70% of the deaths are in developing countries. As of 2017, smoking causes one in ten deaths worldwide, with half of those deaths in the US, China, India and Russia.

Psychology

Takeup

Sigmund Freud, whose doctor assisted his suicide because of oral cancer caused by smoking
 
Most smokers begin smoking during adolescence or early adulthood. Some studies also show that smoking can also be linked to various mental health complications. Smoking has elements of risk-taking and rebellion, which often appeal to young people. The presence of peers that smoke and media featuring high-status models smoking may also encourage smoking. Because teenagers are influenced more by their peers than by adults, attempts by parents, schools, and health professionals at preventing people from trying cigarettes are often unsuccessful.

Children of smoking parents are more likely to smoke than children with non-smoking parents. Children of parents who smoke are less likely to quit smoking. One study found that parental smoking cessation was associated with less adolescent smoking, except when the other parent currently smoked. A current study tested the relation of adolescent smoking to rules regulating where adults are allowed to smoke in the home. Results showed that restrictive home smoking policies were associated with lower likelihood of trying smoking for both middle and high school students.

Behavioural research generally indicates that teenagers begin their smoking habits due to peer pressure, and cultural influence portrayed by friends. However, one study found that direct pressure to smoke cigarettes played a less significant part in adolescent smoking, with adolescents also reporting low levels of both normative and direct pressure to smoke cigarettes. Mere exposure to tobacco retailers may motivate smoking behaviour in adults. A similar study suggested that individuals may play a more active role in starting to smoke than has previously been thought and that social processes other than peer pressure also need to be taken into account. Another study's results indicated that peer pressure was significantly associated with smoking behavior across all age and gender cohorts, but that intrapersonal factors were significantly more important to the smoking behavior of 12- to 13-year-old girls than same-age boys. Within the 14- to 15-year-old age group, one peer pressure variable emerged as a significantly more important predictor of girls' than boys' smoking. It is debated whether peer pressure or self-selection is a greater cause of adolescent smoking.

Psychologists such as Hans Eysenck have developed a personality profile for the typical smoker. Extraversion is the trait that is most associated with smoking, and smokers tend to be sociable, impulsive, risk taking, and excitement seeking individuals. Although personality and social factors may make people likely to smoke, the actual habit is a function of operant conditioning. During the early stages, smoking provides pleasurable sensations (because of its action on the dopamine system) and thus serves as a source of positive reinforcement.

Persistence

The reasons given by some smokers for this activity have been categorized as addictive smoking, pleasure from smoking, tension reduction/relaxation, social smoking, stimulation, habit/automatism, and handling. There are gender differences in how much each of these reasons contribute, with females more likely than males to cite tension reduction/relaxation, stimulation and social smoking.

Some smokers argue that the depressant effect of smoking allows them to calm their nerves, often allowing for increased concentration. However, according to the Imperial College London, "Nicotine seems to provide both a stimulant and a depressant effect, and it is likely that the effect it has at any time is determined by the mood of the user, the environment and the circumstances of use. Studies have suggested that low doses have a depressant effect, while higher doses have stimulant effect."

Patterns

A number of studies have established that cigarette sales and smoking follow distinct time-related patterns. For example, cigarette sales in the United States of America have been shown to follow a strongly seasonal pattern, with the high months being the months of summer, and the low months being the winter months.

Similarly, smoking has been shown to follow distinct circadian patterns during the waking day—with the high point usually occurring shortly after waking in the morning, and shortly before going to sleep at night.

Economic

In countries where there is a universally funded healthcare system, the government covers the cost of medical care for smokers who become ill through smoking in the form of increased taxes. Two broad debating positions exist on this front, the "pro-smoking" argument suggesting that heavy smokers generally don't live long enough to develop the costly and chronic illnesses which affect the elderly, reducing society's healthcare burden, and the "anti-smoking" argument suggests that the healthcare burden is increased because smokers get chronic illnesses younger and at a higher rate than the general population. Data on both positions has been contested. The Centers for Disease Control and Prevention published research in 2002 claiming that the cost of each pack of cigarettes sold in the United States was more than $7 in medical care and lost productivity. The cost may be higher, with another study putting it as high as $41 per pack, most of which however is on the individual and his/her family. This is how one author of that study puts it when he explains the very low cost for others: "The reason the number is low is that for private pensions, Social Security, and Medicare — the biggest factors in calculating costs to society — smoking actually saves money. Smokers die at a younger age and don't draw on the funds they've paid into those systems." Other research demonstrates that premature death caused by smoking may redistribute Social Security income in unexpected ways that affect behavior and reduce the economic well-being of smokers and their dependents. To further support this, whatever the rate of smoking consumption is per day, smokers have a greater lifetime medical cost on average compared to a non-smoker by an estimated $6000. Between the cost for lost productivity and health care expenditures combined, cigarette smoking costs at least 193 billion dollars (Research also shows that smokers earn less money than nonsmokers). As for secondhand smoke, the cost is over 10 billion dollars.

By contrast, some non-scientific studies, including one conducted by Philip Morris in the Czech Republic called Public Finance Balance of Smoking in the Czech Republic and another by the Cato Institute, support the opposite position. Philip Morris has explicitly apologised for the former study, saying: "The funding and public release of this study which, among other things, detailed purported cost savings to the Czech Republic due to premature deaths of smokers, exhibited terrible judgment as well as a complete and unacceptable disregard of basic human values. For one of our tobacco companies to commission this study was not just a terrible mistake, it was wrong. All of us at Philip Morris, no matter where we work, are extremely sorry for this. No one benefits from the very real, serious and significant diseases caused by smoking."

Between 1970 and 1995, per-capita cigarette consumption in poorer developing countries increased by 67 percent, while it dropped by 10 percent in the richer developed world. Eighty percent of smokers now live in less developed countries. By 2030, the World Health Organization (WHO) forecasts that 10 million people a year will die of smoking-related illness, making it the single biggest cause of death worldwide, with the largest increase to be among women. WHO forecasts the 21st century's death rate from smoking to be ten times the 20th century's rate ("Washingtonian" magazine, December 2007).

Health

Cigarette smoking is the leading cause of preventable death and a major public health concern.

There are 1.1 billion tobacco users in the world. One person dies every six seconds from a tobacco related disease.

head and torso of a male with internal organs shown and labels referring to the effects of tobacco smoking
Common adverse effects of tobacco smoking. The more common effects are in bold face.
 
Tobacco use leads most commonly to diseases affecting the heart and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), Idiopathic Pulmonary Fibrosis (IPF), emphysema, and cancer (particularly lung cancer, cancers of the larynx and mouth, esophageal cancer and pancreatic cancer). Cigarette smoking increases the risk of Crohn's disease as well as the severity of the course of the disease. It is also the number one cause of bladder cancer. The smoke from tobacco elicits carcinogenic effects on the tissues of the body that are exposed to the smoke.

Tobacco smoke is a complex mixture of over 5,000 identified chemicals, of which 98 are known to have specific toxicological properties. The most important chemicals causing cancer are those that produce DNA damage since such damage appears to be the primary underlying cause of cancer. Cunningham et al. combined the microgram weight of the compound in the smoke of one cigarette with the known genotoxic effect per microgram to identify the most carcinogenic compounds in cigarette smoke. The seven most important carcinogens in tobacco smoke are shown in the table, along with DNA alterations they cause. 

Cigarette smoking has also been associated with sarcopenia, the age-related loss of muscle mass and strength.

The World Health Organization estimates that tobacco caused 5.4 million deaths in 2004 and 100 million deaths over the course of the 20th century. Similarly, the United States Centers for Disease Control and Prevention describes tobacco use as "the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide." Although 70% of smokers state their intention to quit only 3–5% are actually successful in doing so.

The probabilities of death from lung cancer before age 75 in the United Kingdom are 0.2% for men who never smoked (0.4% for women), 5.5% for male former smokers (2.6% in women), 15.9% for current male smokers (9.5% for women) and 24.4% for male "heavy smokers" defined as smoking more than 5 cigarettes per day (18.5% for women). Tobacco smoke can combine with other carcinogens present within the environment in order to produce elevated degrees of lung cancer. 

Rates of smoking have generally leveled-off or declined in the developed world. Smoking rates in the United States have dropped by half from 1965 to 2006, falling from 42% to 20.8% in adults. In the developing world, tobacco consumption is rising by 3.4% per year.

Second-hand smoke presents a known health risk, to which six hundred thousand deaths were attributed in 2004. It also has been known to produce skin conditions such as freckles and dryness.

In 2015, a meta-analysis found that smokers were at greater risk of developing psychotic illness. Tobacco has also been described an anaphrodisiac due to its propensity for causing erectile dysfunction.

Social

Famous smokers of the past used cigarettes or pipes as part of their image, such as Jean-Paul Sartre's Gauloises-brand cigarettes; Albert Einstein's, Douglas MacArthur's, Bertrand Russell's, and Bing Crosby's pipes; or the news broadcaster Edward R. Murrow's cigarette. Writers in particular seem to be known for smoking, for example, Cornell Professor Richard Klein's book Cigarettes are Sublime for the analysis, by this professor of French literature, of the role smoking plays in 19th and 20th century letters. The popular author Kurt Vonnegut addressed his addiction to cigarettes within his novels. British Prime Minister Harold Wilson was well known for smoking a pipe in public as was Winston Churchill for his cigars. Sherlock Holmes, the fictional detective created by Sir Arthur Conan Doyle smoked a pipe, cigarettes, and cigars. The DC Vertigo comic book character, John Constantine, created by Alan Moore, is synonymous with smoking, so much so that the first storyline by Preacher creator, Garth Ennis, centered around John Constantine contracting lung cancer. Professional wrestler James Fullington, while in character as "The Sandman", is a chronic smoker in order to appear "tough". 

The problem of smoking at home is particularly difficult for women in many cultures (especially Arab cultures), where it may not be acceptable for a woman to ask her husband not to smoke at home or in the presence of her children. Studies have shown that pollution levels for smoking areas indoors are higher than levels found on busy roadways, in closed motor garages, and during fire storms. Furthermore, smoke can spread from one room to another, even if doors to the smoking area are closed.

The ceremonial smoking of tobacco, and praying with a sacred pipe, is a prominent part of the religious ceremonies of a number of Native American Nations. Sema, the Anishinaabe word for tobacco, is grown for ceremonial use and considered the ultimate sacred plant since its smoke is believed to carry prayers to the spirits. In most major religions, however, tobacco smoking is not specifically prohibited, although it may be discouraged as an immoral habit. Before the health risks of smoking were identified through controlled study, smoking was considered an immoral habit by certain Christian preachers and social reformers. The founder of the Latter Day Saint movement, Joseph Smith, recorded that on 27 February 1833, he received a revelation which discouraged tobacco use. This "Word of Wisdom" was later accepted as a commandment, and faithful Latter-day Saints abstain completely from tobacco. Jehovah's Witnesses base their stand against smoking on the Bible's command to "clean ourselves of every defilement of flesh" (2 Corinthians 7:1). The Jewish Rabbi Yisrael Meir Kagan (1838–1933) was one of the first Jewish authorities to speak out on smoking. In Ahmadiyya Islam, smoking is highly discouraged, although not forbidden. During the month of fasting however, it is forbidden to smoke tobacco. In the Bahá'í Faith, smoking tobacco is discouraged though not forbidden.

Incomes

One of the largest global enterprises in the world is known to be the tobacco industry. The six biggest tobacco companies made a combined profit of $35.1 billion (Jha et al., 2014) in 2010.

Public policy

On 27 February 2005 the WHO Framework Convention on Tobacco Control, took effect. The FCTC is the world's first public health treaty. Countries that sign on as parties agree to a set of common goals, minimum standards for tobacco control policy, and to cooperate in dealing with cross-border challenges such as cigarette smuggling. Currently the WHO declares that 4 billion people will be covered by the treaty, which includes 168 signatories. Among other steps, signatories are to put together legislation that will eliminate secondhand smoke in indoor workplaces, public transport, indoor public places and, as appropriate, other public places.

Taxation

Many governments have introduced excise taxes on cigarettes in order to reduce the consumption of cigarettes.

In 2002, the Centers for Disease Control and Prevention said that each pack of cigarettes sold in the United States costs the nation more than $7 in medical care and lost productivity, around $3400 per year per smoker. Another study by a team of health economists finds the combined price paid by their families and society is about $41 per pack of cigarettes.

Substantial scientific evidence shows that higher cigarette prices result in lower overall cigarette consumption. Most studies indicate that a 10% increase in price will reduce overall cigarette consumption by 3% to 5%. Youth, minorities, and low-income smokers are two to three times more likely to quit or smoke less than other smokers in response to price increases. Smoking is often cited as an example of an inelastic good, however, i.e. a large rise in price will only result in a small decrease in consumption.

Many nations have implemented some form of tobacco taxation. As of 1997, Denmark had the highest cigarette tax burden of $4.02 per pack. Taiwan only had a tax burden of $0.62 per pack. The federal government of the United States charges $1.01 per pack.

Cigarette taxes vary widely from state to state in the United States. For example, Missouri has a cigarette tax of only 17 cents per pack, the nation's lowest, while New York has the highest cigarette tax in the U.S.: $4.35 per pack. In Alabama, Illinois, Missouri, New York City, Tennessee, and Virginia, counties and cities may impose an additional limited tax on the price of cigarettes. Sales taxes are also levied on tobacco products in most jurisdictions. 

In the United Kingdom, a packet of 20 cigarettes typically costs between £8.00 to £12.00 according to 2018 prices, depending on the brand purchased and where the purchase was made. The UK has a significant black market for tobacco, and it has been estimated by the tobacco industry that 27% of cigarette and 68% of handrolling tobacco consumption is non-UK duty paid (NUKDP).

In Australia total taxes account for 62.5% of the final price of a packet of cigarettes (2011 figures). These taxes include federal excise or customs duty and Goods and Services Tax.

Restrictions

An enclosed smoking area in a Japanese train station. Notice the air vent on the roof.
 
In June 1967, the US Federal Communications Commission ruled that programmes broadcast on a television station which discussed smoking and health were insufficient to offset the effects of paid advertisements that were broadcast for five to ten minutes each day. In April 1970, the US Congress passed the Public Health Cigarette Smoking Act banning the advertising of cigarettes on television and radio starting on 2 January 1971.

The Tobacco Advertising Prohibition Act 1992 expressly prohibited almost all forms of Tobacco advertising in Australia, including the sponsorship of sporting or other cultural events by cigarette brands. 

All tobacco advertising and sponsorship on television has been banned within the European Union since 1991 under the Television Without Frontiers Directive (1989). This ban was extended by the Tobacco Advertising Directive, which took effect in July 2005 to cover other forms of media such as the internet, print media, and radio. The directive does not include advertising in cinemas and on billboards or using merchandising – or tobacco sponsorship of cultural and sporting events which are purely local, with participants coming from only one Member State as these fall outside the jurisdiction of the European Commission. However, most member states have transposed the directive with national laws that are wider in scope than the directive and cover local advertising. A 2008 European Commission report concluded that the directive had been successfully transposed into national law in all EU member states, and that these laws were well implemented.

Some countries also impose legal requirements on the packaging of tobacco products. For example, in the countries of the European Union, Turkey, Australia and South Africa, cigarette packs must be prominently labeled with the health risks associated with smoking. Canada, Australia, Thailand, Iceland and Brazil have also imposed labels upon cigarette packs warning smokers of the effects, and they include graphic images of the potential health effects of smoking. Cards are also inserted into cigarette packs in Canada. There are sixteen of them, and only one comes in a pack. They explain different methods of quitting smoking. Also, in the United Kingdom, there have been a number of graphic NHS advertisements, one showing a cigarette filled with fatty deposits, as if the cigarette is symbolizing the artery of a smoker. 

Many countries have a smoking age. In many countries, including the United States, most European Union member states, New Zealand, Canada, South Africa, Israel, India, Brazil, Chile, Costa Rica and Australia, it is illegal to sell tobacco products to minors and in the Netherlands, Austria, Belgium, Denmark and South Africa it is illegal to sell tobacco products to people under the age of 16. On 1 September 2007 the minimum age to buy tobacco products in Germany rose from 16 to 18, as well as in the United Kingdom where on 1 October 2007 it rose from 16 to 18. Underlying such laws is the belief that people should make an informed decision regarding the risks of tobacco use. These laws have a lax enforcement in some nations and states. In China, Turkey, and many other countries usually a child will have little problem buying tobacco products, because they are often told to go to the store to buy tobacco for their parents. 

Several countries such as Ireland, Latvia, Estonia, the Netherlands, Finland, Norway, Canada, Australia, Sweden, Portugal, Singapore, Italy, Indonesia, India, Lithuania, Chile, Spain, Iceland, United Kingdom, Slovenia, Turkey and Malta have legislated against smoking in public places, often including bars and restaurants. Restaurateurs have been permitted in some jurisdictions to build designated smoking areas (or to prohibit smoking). In the United States, many states prohibit smoking in restaurants, and some also prohibit smoking in bars. In provinces of Canada, smoking is illegal in indoor workplaces and public places, including bars and restaurants. As of 31 March 2008 Canada has introduced a smoke-free law ban in all public places, as well as within 10 metres of an entrance to any public place. In Australia, smoke-free laws vary from state to state. Currently, Queensland has completely smoke-free indoor public places (including workplaces, bars, pubs and eateries) as well as patrolled beaches and some outdoor public areas. There are, however, exceptions for designated smoking areas. In Victoria, smoking is restricted in railway stations, bus stops and tram stops as these are public locations where second-hand smoke can affect non-smokers waiting for public transport, and since 1 July 2007 is now extended to all indoor public places. In New Zealand and Brazil, smoking is restricted in enclosed public places including bars, restaurants and pubs. Hong Kong restricted smoking on 1 January 2007 in the workplace, public spaces such as restaurants, karaoke rooms, buildings, and public parks (bars which do not admit minors were exempt until 2009). In Romania smoking is illegal in trains, metro stations, public institutions (except where designated, usually outside) and public transport. In Germany, additionally to smoking bans in public buildings and transports, an anti-smoking ordinance for bars and restaurants was implemented in late 2007. A study by the University of Hamburg (Ahlfeldt and Maennig 2010) demonstrates, that the smoking ban had, if any, only short run impacts on bar and restaurant revenues. In the medium and long run no negative effect was measurable. The results suggest either, that the consumption in bars and restaurants is not affected by smoking bans in the long run, or, that negative revenue impacts by smokers are compensated by increasing revenues through non-smokers.

Ignition safety

An indirect public health problem posed by cigarettes is that of accidental fires, usually linked with consumption of alcohol. Enhanced combustion using nitrates was traditionally used but cigarette manufacturers have been silent on this subject claiming at first that a safe cigarette was technically impossible, then that it could only be achieved by modifying the paper. Roll your own cigarettes contain no additives and are fire safe. Numerous fire safe cigarette designs have been proposed, some by tobacco companies themselves, which would extinguish a cigarette left unattended for more than a minute or two, thereby reducing the risk of fire. Among American tobacco companies, some have resisted this idea, while others have embraced it. RJ Reynolds was a leader in making prototypes of these cigarettes in 1983 and will make all of their U.S. market cigarettes to be fire-safe by 2010. Phillip Morris is not in active support of it. Lorillard (purchased by RJ Reynolds), the US' 3rd-largest tobacco company, seems to be ambivalent.

Gateway drug theory

The relationship between tobacco and other drug use has been well-established, however the nature of this association remains unclear. The two main theories are the phenotypic causation (gateway) model and the correlated liabilities model. The causation model argues that smoking is a primary influence on future drug use, while the correlated liabilities model argues that smoking and other drug use are predicated on genetic or environmental factors.

Cessation

Smoking cessation, referred to as "quitting", is the action leading towards abstinence of tobacco smoking. Methods of "quitting" include advice from physicians or social workers, cold turkey, nicotine replacement therapy, contingent vouchers, antidepressants, hypnosis, self-help (mindfulness meditation), and support groups. A meta-analysis from 2018, conducted on 61 RCT, showed that one year after people quit smoking with the assistance of first‐line smoking cessation medications (and some behavioral help), only a little under 20% of smokers remained sustained abstinence.

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