Psychoactive Drug

A psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that crosses the blood–brain barrier and acts primarily upon the central nervous system where it affects brain function, resulting in alterations in perception, mood, consciousness, cognition, and behavior. These substances may be used recreationally, to purposefully alter one's consciousness, as entheogens, for ritual, spiritual, and/or shamanic 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 health risks or negative consequences. With sustained use of some substances, psychological and physical dependence ("addiction") may develop, making the cycle of abuse even more difficult to interrupt. Drug rehabilitation aims to break this cycle of dependency, through a combination of psychotherapy, support groups and even other psychoactive substances. However, the reverse is also true in some cases, that is certain experiences on drugs may be so unfriendly and uncomforting that the user may never want to try the substance again. This is especially true of the deliriants (e.g. Jimson weed) and powerful dissociatives (e.g. Salvia divinorum). Most purely psychedelic drugs are considered to be non-addictive (LSD, psilocybin, mescaline etc.); "psychedelic amphetamines" or empathogen-entactogens (such as MDA, MDMA etc.) may produce an additional stimulant and/or euphoriant effect, and thus have an addiction potential.

In part because of this potential for abuse and dependency, the ethics of drug use are the subject of debate. Many governments worldwide place restrictions on drug production and sales in an attempt to decrease drug abuse. Ethical concerns have also been raised about over-use of these drugs clinically, and about their marketing by manufacturers.