Psychoactive drug

From Wikipedia, the free encyclopedia

An assortment of psychoactive drugs
An assortment of psychoactive drugs

A psychoactive drug or psychotropic substance is a chemical substance that acts primarily upon the central nervous system where it alters brain function, resulting in temporary changes in perception, mood, consciousness and behaviour. These drugs may be used recreationally to purposefully alter one's consciousness, as entheogens for ritual or spiritual purposes, as a tool for studying or augmenting the mind, or therapeutically as medication.

Because psychoactive substances bring about subjective changes in consciousness and mood that the user may find pleasant (e.g. euphoria) or advantageous (e.g. increased alertness), many psychoactive substances are abused, that is, used excessively, despite risks or negative consequences. With sustained use of some substances, physical dependence may develop, making the cycle of abuse even more difficult to interrupt. Drug rehabilitation can involve a combination of psychotherapy, support groups and even other psychoactive substances to break the cycle of dependency.

In part because of this potential for abuse and dependency, the ethics of drug use are the subject of a continuing philosophical debate. Many governments worldwide have placed restrictions on drug production and sales in an attempt to decrease drug abuse.

Contents

[edit] History

Drug use is a practice that dates to prehistoric times. There is archaeological evidence of the use of psychoactive substances dating back at least 10,000 years, and historical evidence of cultural use over the past 5,000 years.[1] While medicinal use seems to have played a very large role, it has been suggested that the urge to alter one's consciousness is as primary as the drive to satiate thirst, hunger or sexual desire.[2] Others suggest that marketing, availability or the pressures of modern life are why humans use so many psychoactives in their daily lives. However, the long history of drug use and even children's desire for spinning, swinging, or sliding indicates that the drive to alter one's state of mind is universal.[3]

This relationship is not limited to humans. A number of animals consume different psychoactive plants, animals, berries and even fermented fruit, becoming intoxicated, such as cats after consuming catnip. Traditional legends of sacred plants often contain references to animals that introduced humankind to their use.[4] Biology suggests an evolutionary connection between psychoactive plants and animals, as to why these chemicals and their receptors exist within the nervous system.[5]

The 20th century has seen governments initially responding to many drugs by banning them and making their use, supply or trade a criminal offense. A notable example of this is the Prohibition era in the United States, where alcohol was made illegal for 13 years. However, many governments have concluded that illicit drug use cannot be sufficiently stopped through criminalization. In some countries, there has been a move toward harm reduction by health services, where the use of illicit drugs is neither condoned nor promoted, but services and support are provided to ensure users have the negative effects of their illicit drug use minimized. This can go hand-in-hand with supply reduction strategies by law-enforcement agencies.

[edit] Uses of psychoactive substances

Psychoactive substances are used by humans for a number of different purposes, both legal and illicit.

[edit] Anesthesia

Main article: Anesthesia

General anesthetics are a class of psychoactive drug used on patients to block pain and other sensations. Most anesthetics induce unconsciousness, which allows patients to undergo medical procedures like surgery without physical pain or emotional trauma.[6] To induce unconsciousness, anesthetics affect the GABA and NMDA systems. For example, halothane is a GABA agonist,[7] and ketamine is an NMDA receptor antagonist.[8]

[edit] Painkillers

Main article: Analgesics
Aspirin
Aspirin

Psychoactive drugs are often prescribed to manage pain. As the subjective experience of pain is regulated by endorphins, neurochemicals that are endogenous opioids, pain can be managed using psychoactives that operate on this neurotransmitter system. This class of drugs includes narcotics, like morphine and codeine,[9] and also NSAIDs such as aspirin and ibuprofen.

[edit] Psychiatric medications

Main article: Psychiatric medications
Zoloft, an antidepressant (and anti-anxiety) medication
Zoloft, an antidepressant (and anti-anxiety) medication

Psychiatric medications are prescribed for the management of mental and emotional disorders. There are 6 major classes of psychiatric medications:

[edit] Recreational drugs

Main article: Recreational drug use

Many psychoactive substances are used for their mood and perception altering effects, including those with accepted uses in medicine and psychiatry. Classes of drugs frequently used recreationally include:

Examples include caffeine, alcohol, cocaine, LSD, and cannabis.[11]

In many cultures, possessing or having used recreational drugs is seen as a status symbol. Recreational drugs, especially those known as club drugs, are seen as status symbols at social events such as at nightclubs and parties.[12] This is true of many cultures throughout history; drugs have been viewed as status symbols since ancient times. For example, in ancient Egypt, gods were commonly pictured holding hallucinogenic plants.[13]

[edit] Ritual and spiritual use

Timothy Leary was a leading proponent of spiritual hallucinogen use.
Timothy Leary was a leading proponent of spiritual hallucinogen use.
Main article: Entheogens

Certain psychoactives, particularly hallucinogens, have been used for religious purposes since prehistoric times. Native Americans have used mescaline-containing peyote cacti for religious ceremonies for as long as 5700 years.[14] The muscimol-containing Amanita muscaria mushroom was used for ritual purposes throughout prehistoric Europe.[15] Various other hallucinogens, including jimsonweed, psilocybin mushrooms, and cannabis have been used in religious ceremonies for centuries.[16] There is speculation that hallucinogenic mushrooms and cacti greatly influenced the major religions of India, North and South America, the Middle East, and Europe, including Christianity.[16]

The use of entheogens for religious purposes resurfaced in the West during the counterculture movements of the 1960s and 70s. Under the leadership of Timothy Leary, new religious movements began to use LSD and other hallucinogens as sacraments.[17] In the United States, the use of peyote for ritual purposes is protected only for members of the Native American Church, which is allowed to cultivate and distribute peyote. However, the bona fide religious use of Peyote, regardless of ancestry, is protected in Colorado, Arizona, New Mexico, Nevada, and Oregon.[18]

[edit] Administration

For a substance to be psychoactive, it must cross the blood-brain barrier so it can affect neurochemical function. Psychoactive drugs are administered in several different ways. In medicine, most psychiatric drugs, such as fluoxetine, quetiapine, and lorazepam are ingested orally in tablet or capsule form. However, certain medical psychoactives are administered via inhalation, injection, or rectal suppository/enema. Recreational drugs can be administered in several additional ways that are not common in medicine. Certain drugs, such as alcohol and caffeine, are ingested in beverage form; nicotine and cannabis are often smoked; peyote and psilocybin mushrooms are ingested in botanical form or dried; and certain crystalline drugs such as cocaine and methamphetamines are often insufflated. The efficiency of each method of administration varies from drug to drug.[19]

[edit] Effects

[edit] Subjective and behavioral effects

The following Venn diagram attempts to organize and provide a basic overview of the most common psychoactive drugs into intersecting groups and subgroups based upon the subjective and behavioral effects they cause in humans as well as by their pharmacological classification.[20][21][22][23][24] Items within each subgroup are close to those of most similar method of action, and also follow a general placement in accordance with the legend below the diagram. Primary intersections are represented via color mixing.


Image:PsychoactiveChart.svg

Legend

Primary groups

  • Blue: Stimulants generally increase in potency to the upper left.
  • Red: Depressants generally increase in potency to the lower right.
  • Green: Hallucinogens are psychedelic to the left, dissociative to the right, generally less predictable down and to the right, and generally more potent towards the bottom.
  • Pink: Antipsychotics are generally more sedative/tranquilizing to the right.
Secondary groups
  • Cyan (light blue): Overlap of Stimulants (Blue) and Psychedelic hallucinogens (Green) — Primary psychedelics exhibit a stimulant effect
  • Yellow : Overlap of Depressants (Red) and Dissociative hallucinogens (Green) — Primary dissociatives exhibit a depressant effect
  • Lavender: Overlap of Stimulants (Blue) and Antipsychotics (Pink) - The modern non-sedating antidepressants.
  • Salmon: Overlap of Depressants (Red) and Antipsychotics (Pink) - The older sedating antidepressants and anxiolytics.
Tertiary groups
  • Magenta (purple): Overlap of Stimulants (Blue) and Depressants (Red) — Example: nicotine exhibits effects of both.
  • White: Overlap of Stimulants, Depressants and Hallucinogens — Example: THC exhibits effects of all three sections.
  • Sky-blue: Overlap of Stimulants, Psychedelic hallucinogens and Antipsychotics - The empathogens / entactogens.
  • Peach: Overlap of Depressants, Dissociative hallucinogens and Antipsychotics
Quaternary group
  • Light-pink: Center overlap of all four sections (Stimulants, Depressants, Hallucinogens and Antipsychotics) - Cannabis, containing both THC and CBD, exhibits a mix of all sections, leaning towards the hallucinogen section due to THC being the primary constituent.
Illustration of the major elements of neurotransmission. Depending on its method of action, a psychoactive substance may block the receptors on the post-synaptic neuron (dendrite), or block reuptake or affect neurotransmitter synthesis in the pre-synaptic neuron (axon).
Illustration of the major elements of neurotransmission. Depending on its method of action, a psychoactive substance may block the receptors on the post-synaptic neuron (dendrite), or block reuptake or affect neurotransmitter synthesis in the pre-synaptic neuron (axon).
Main article: Neuropsychopharmacology

Psychoactive drugs operate by temporarily affecting a person's neurochemistry, which in turn causes changes in a person's mood, cognition, perception and behavior. There are many ways in which psychoactive drugs can affect the brain. Each drug has a specific action on one or more neurotransmitter or neuroreceptor in the brain.

Drugs that increase activity in particular neurotransmitter systems are called agonists. They act by increasing the synthesis of one or more neurotransmitters or reducing its reuptake from the synapses. Drugs that reduce neurotransmitter activity are called antagonists, and operate by interfering with synthesis or blocking postsynaptic receptors so that neurotransmitters cannot bind to them.[25]

Exposure to a psychoactive substance can cause changes in the structure and functioning of neurons, as the nervous system tries to re-establish the homeostasis disrupted by the presence of the drug. Exposure to antagonists for a particular neurotransmitter increases the number of receptors for that neurotransmitter, and the receptors themselves become more sensitive. This is called sensitization. Conversely, overstimulation of receptors for a particular neurotransmitter causes a decrease in both number and sensitivity of these receptors, a process called desensitization or tolerance. Sensitization and desensitization are more likely to occur with long-term exposure, although they may occur after only a single exposure. These processes are thought to underlie addiction.[26]

[edit] Affected neurotransmitter systems

The following is a brief table of notable drugs and their primary neurotransmitter, receptor or method of action. It should be noted that many drugs act on more than one transmitter or receptor in the brain.[27]

Neurotransmitter/receptor Classification Examples

Acetylcholine
 Cholinergics (acetylcholine agonists) nicotine, piracetam
Anticholinergics (acetylcholine antagonists) scopolamine, dimenhydrinate, diphenhydramine
Adenosine
 Adenosine receptor antagonists[28] caffeine, theobromine, theophylline

Dopamine
 Dopamine reuptake inhibitors (DRIs) cocaine, methylphenidate
Dopamine receptor antagonists haloperidol, droperidol


GABA
 GABA reuptake inhibitors tiagabine
GABA receptor agonists ethanol, barbiturates, diazepam, muscimol, ibotenic acid
GABA antagonists thujone, bicuculline

Norepinephrine
 Norepinephrine reuptake inhibitors amoxapine, atomoxetine
Norepinephrine releasers mianserin
Serotonin
 Serotonin receptor agonists LSD, psilocybin, mescaline, DMT
Selective serotonin reuptake inhibitors (SSRIs) fluoxetine, sertraline
Serotonin releasers MDMA (ecstasy)
AMPA receptor
 AMPA receptor antagonists kynurenic acid, NBQX
Cannabinoid receptor
 Cannabinoid receptor agonists THC
Melanocortin receptor
 Melanocortin receptor agonists bremelanotide
NMDA receptor
 NMDA receptor antagonists ketamine, PCP, DXM
Opioid receptor
 μ-opioid receptor agonists morphine, heroin, oxycodone
μ-opioid receptor inverse agonists naloxone, naltrexone
κ-opioid receptor agonists salvinorin A, butorphanol, nalbuphine
Monoamine oxidase
 Monoamine oxidase inhibitors (MAOIs) phenelzine, iproniazid
bind to MAO protein transporter amphetamine, methamphetamine

[edit] Addiction

Main article: Addiction
Heroin bottle
Heroin bottle

Psychoactive drugs are often associated with addiction. Addiction can be divided into two types: psychological addiction, by which a user feels compelled to use a drug despite negative physical or societal consequence, and physical dependence, by which a user must use a drug to avoid medically harmful withdrawal.[29] Not all drugs are physically addictive, but any activity that stimulates the brain's dopaminergic reward system — typically, any pleasurable activity[30] — can lead to psychological addiction.[29] Drugs that are most likely to cause addiction are drugs that directly stimulate the dopaminergic system, like cocaine and amphetamines. Drugs that only indirectly stimulate the dopaminergic system, such as psychedelics, are not as likely to be addictive.

Because so many consumers want to reduce or eliminate their own use of psychoactive drugs,[31] many professionals, self-help groups, and businesses specialize in drug rehabilitation, with varying degrees of success. Many parents attempt to influence the actions and choices of their children regarding psychoactives.[32]

Common forms of rehabilitation include psychotherapy, support groups and pharmacotherapy, which uses psychoactive substances to reduce cravings and physiological withdrawal symptoms while a user is going through detox. Methadone, itself an opioid and a psychoactive substance, is a common treatment for heroin addiction. Recent research on addiction has shown some promise in using psychedelics to treat and even cure addictions, although this has yet to become a widely accepted practice.[33][34]

[edit] Legitimacy

Many recreational drugs are heavily regulated, an indication of widespread moral objection to variation in recreational psychoactive drug use. However, critics believe that regulation of recreational drug use is a violation of personal autonomy and freedom.[35]

“ We're playing with half a deck as long as we tolerate that the cardinals of government and science should dictate where human curiousity can legitimately send its attention and where it can not. It's an essentially preposterous situation. It is essentially a civil rights issue, because what we're talking about here is the repression of a religious sensibility. In fact, not a religious sensibility, the religious sensibility.”

Terence McKenna in: Non-Ordinary States Through Vision Plants, Sound Photosynthesis, Mill Valley CA., 1988, ISBN 1-569-64709-7

In the United States, critics have noted that prohibition or regulation of recreational and spiritual drug use might be unconstitutional.[36] Because there is controversy about regulation of recreational drugs, there is an ongoing debate about drug prohibition. At the beginning of the 21st century, legally prescribed illegal psychoactive drugs used for legitimate purposes have been targeted by the US Justice System.[37]

“ The use of drugs to alter consciousness is nothing new. [...]
  It is my belief that the desire to alter consciousness periodically is an innate, normal drive analogous to hunger or the sexual drive. Note that I do not say ‘desire to alter consciousness by means of chemical agents.’ Drugs are merely one means of satisfying this drive; there are many others, and I will discuss them in due course. [...] Furthermore, the need for periods of nonordinary consciousness begins to be expressed at ages far too young for it to have much to do with social conditioning. Anyone who watches very young children without revealing his presence will find them regularly practicing techniques that induce striking changes in mental states. Three- and four-year-olds, for example, commonly whirl themselves into vertiginous stupors. They hyperventilate and have other children squeeze them around the chest until they faint. They also choke each other to produce loss of consciousness.
  To my knowledge these practices appear spontaneously among children of all societies, and I suspect they have done so throughout history as well. In our society, children quickly learn to keep this sort of play out of sight of grownups, who instinctively try to stop them.”

Andrew Weil: The Natural Mind—An Investigation of Drugs and the Higher Consciousness, Houghton Mifflin, 1985, chapter 2 “Why People Take Drugs”, pp. 17–20, ISBN 0-395-91156-7

[edit] Legality

The legality of psychoactive drugs has been controversial through most of history; the Opium Wars and Prohibition are two historical examples of legal controversy surrounding psychoactive drugs. However, in recent years, the most influential document regarding the legality of psychoactive drugs is the Single Convention on Narcotic Drugs, an international treaty signed in 1961 as an Act of the United Nations. Signed by 73 nations including the United States, the USSR, India, and the United Kingdom, the Single Convention on Narcotic Drugs established Schedules for the legality of each drug and laid out an international agreement to fight addiction to recreational drugs by combatting the sale, trafficking, and use of scheduled drugs.[38] All countries that signed the treaty passed laws to implement these rules within their borders. However, some countries that signed the Single Convention on Narcotic Drugs, such as the Netherlands, are more lenient with their enforcement of these laws.[39]

In the United States, the Food and Drug Administration (FDA) has authority over all drugs, including psychoactive drugs. The FDA regulates which psychoactive drugs are over the counter and which are only available with a prescription.[40] However, certain psychoactive drugs, like alcohol, tobacco, and drugs listed in the Single Convention on Narcotic Drugs are subject to criminal laws. The Controlled Substances Act of 1970 regulates the recreational drugs outlined in the Single Convention on Narcotic Drugs.[41] Alcohol is regulated by state governments, but the federal National Minimum Drinking Age Act penalizes states for not following a national drinking age.[42] Tobacco is also regulated by all fifty state governments.[43] Most people accept such restrictions and prohibitions of certain drugs, especially the "hard" drugs, which are illegal in most countries.[44][45][46]

In the medical context, psychoactive drugs as a treatment for illness is widespread and generally accepted. Little controversy exists concerning over the counter psychoactive medications in antiemetics and antitussives. Psychoactive drugs are commonly prescribed to patients with psychiatric disorders. However, certain critics believe that certain prescription psychoactives, such as antidepressants and stimulants, are overprescribed and threaten patients' judgement and autonomy.[47][48]

[edit] See also

[edit] References

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