Psychoactive drug

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 behavior. These drugs may be used recreationally to purposefully alter one's consciousness, as entheogens for ritual or spiritual purposes, or as medication.

Many of these substances (especially the stimulants and depressants) can be habit-forming, causing chemical dependency and may lead to substance abuse. Conversely, others (namely the psychedelics) can help to treat and even cure such addictions.

An assortment of psychoactive drugs

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. 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. 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, sliding indicates that the drive to alter one's state of mind is universal.

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

The 20th century has seen governments initially responding to many drugs by banning them and making their use, supply or trade a criminal offence. 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.

Uses of psychoactive substances

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

Painkillers

Main article: Analgesics

As the subjective experience of pain is regulated by endorphins, neurochemicals that are endogenous opioids, pain can be managed using psychoactives that affect this neurotransmitter system.

Psychiatric medications

Main article: Psychiatric medications

Psychiatric medications are prescribed for the management of mental and emotional disorders. There are 6 major classes of psychiatric medications: antidepressants, stimulants, antipsychotics, mood stabilizers, anxiolytics and hypnotics.

Recreational drugs

Main article: Recreational drug use

Many psychoactive substances are used/abused for their mood and perception altering effects, including those with accepted uses in medicine and psychiatry. Classes of drugs frequently used recreationally include stimulants, hallucinogens, hypnotics, analgesics and dissociatives. Examples include coffee, alcohol, cocaine and cannabis.

Ritual and spiritual use

Main article: Entheogens

Psychoactives have been used for many millenia for ritual and spiritual practice, such as the mescaline-containing peyote cactus or psilocybin-containing mushrooms.

Methods of administration

For a substance to be psychoactive, it must cross the blood-brain barrier so it can affect neurochemical function. There are a number of ways that a drug can be taken or administered so it reaches the brain. The fewer systems the drug has to pass through on its way to the brain, the more efficient and therefore potent it will be. In order from least efficient to most efficient:

• Ingestion - consuming a substance through the mouth, allowing it to enter the bloodstream through the gastrointestinal tract, for example alcohol.
• Smoking - burning the substance and inhaling the resulting smoke and vapor, for example cannabis.
• Inhalation - breathing in the fumes of a gaseous substance, for example nitrous oxide.
• Snorting - inhaling the substance through the nose, allowing it to enter the bloodstream through the mucuous membranes lining the sinus cavity, for example cocaine.
• Intramuscular/Intravenous - using a needle and syringe to deliver a substance directly to the bloodstream or muscle tissue, for example heroin.
• Anally - Some drugs, such as opiates and MDMA, can result in higher bioavailability when administered anally. This is because it bypasses the first-pass metabolism of the liver.

Effects

Main article: Neuropsychopharmacology § Neurotransmission

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.

Classification

Psychoactive substances can be classified according to the neurotransmitter system they affect and their subjective and behavioral effects.

Classification by affected neurotransmitter system

The following is a classification of notable drugs by their primary effects on their respective neurotransmitters or receptors. However, it should be noted that most drugs act on more than one transmitter or receptor in the brain.

Neurotransmitter/receptor	Classification	Examples
Serotonin	Serotonin receptor agonists	LSD, psilocybin, mescaline, DMT
	Selective serotonin reuptake inhibitors (SSRIs)	fluoxetine, sertraline
	Serotonin releasers	MDMA (ecstasy)
GABA	GABA receptor agonists	ethanol, barbiturates, diazepam, thujone
	GABA reuptake inhibitors	tiagabine
	GABA receptor selective agonists	muscimol, ibotenic acid
Opioid receptor	μ-opioid receptor agonists	morphine, heroin, oxycodone
	μ-opioid receptor inverse agonists	naloxone, naltrexone
	κ-opioid receptor agonists	salvinorin A, butorphanol, nalbuphine
Dopamine	Dopamine protein transporter blockers	cocaine
	Dopamine receptor antagonists	haloperidol, droperidol
Monoamine oxidase (MAO)	Monoamine oxidase inhibitors (MAOIs)	phenelzine, iproniazid
	bind to MAO protein transporter	amphetamine, methamphetamine
NMDA receptor	NMDA receptor antagonists	ketamine, PCP, DXM
Norepinephrine	Norepinephrine reuptake inhibitors	amoxapine, atomoxetine
	Norepinephrine releasers	mianserin
Cannabinoid receptor	Cannabinoid receptor agonists	THC
Acetylcholine	Cholinergics (acetylcholine agonists)	nicotine, piracetam
	Anticholinergics (acetylcholine antagonists)	scopolamine, dimenhydrinate, diphenhydramine
Adenosine	Methlyxanthines (adenosine receptor antagonists)	caffeine
AMPA receptor	AMPA receptor antagonists	kynurenic acid, NBQX
Melanocortin receptor	Melanocortin receptor agonists	bremelanotide

Classification by 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 the subjective and behavioral effects they cause in humans as well as by their pharmacological classification. 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.

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.

Addiction

Main article: Addiction

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. Not all drugs are physically addictive, but any activity that stimulates the brain's dopaminergic reward system — typically, any pleasurable activity — can lead to psychological addiction. 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, many professionals, self-help groups, and businesses specialize in that field, with varying degrees of success. Many parents attempt to influence the actions and choices of their children regarding psychoactives.

Legality and ethics

For thousands of years, people have studied psychoactive drugs, both by observation and ingestion. However, humanity remains bitterly divided regarding psychoactive drugs, and their value and use has long been an issue of major philosophical and moral contention, even to the point of war (the Opium Wars being a prime example of a war being fought over psychoactives, though moreover it was a prime example of British Imperialism and exploitation of China). A majority of youths and adults consume one or more psychoactive drugs. In the West, the most common by numbers of users are caffeine, alcohol, and nicotine, in that order. Most people accept restrictions on some and the prohibition of others, especially the "hard" drugs, which are generally illegal in most countries. It is interesting to note that some of the most popular recreational drugs such as alcohol or tobacco are legal, despite being considered hard drugs by many. At the same time many soft drugs such as cannabis or psilocybin are illegal and in many cases the most tightly controlled (in the US for example both cannabis and psilocybin are Schedule I drugs, a section reserved for the most dangerous of drugs). This has led many to believe that current prohibition laws are more political in nature.

Debate continues over whether each psychoactive drug being considered is or is not spiritual, sinful, therapeutic, poisonous, ethical, immoral, effective, risky, responsible, recreational, a weapon to use against enemies, a boost to the economy, etc. These attitudes can often be deeply rooted in philosophical and/or religious beliefs, making it difficult to reach consensus on acceptable moral, philosophical, and pragmatic stances regarding psychoactive drugs. A major point of contention regards the role of government: should it (for each drug) remain neutral, prohibit, require a prescription, regulate trade, restrict advertising, promote abstention, promote moderation, and/or educate for safety, as well as whether any existing penalties or enforcement should be changed.

See also

• Antipsychotics
• Arguments for and against drug prohibition
• Contact high
• Demand reduction
• Depressants
• Drug addiction
• Drug rehabilitation
• Entheogens
• Freedom of thought
• Hard drug
• Hallucinogens

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• Medication
• Neuropsychopharmacology
• Poly drug use
• Psychedelics, dissociatives and deliriants
• Psychiatric medications
• Recreational drug use
• Responsible drug use
• Soft drug
• Stimulants
• Substance abuse

External links

• Erowid – Extensive portal primarily relating to psychoactive drugs (Wikipedia article about the website – Erowid)
• The Lycæum – Lycaeum Synaesthesia (similar website)
• Neuroscience of Psychoactive Substance Use and Dependence by the WHO –