A psychoactive drug, psychopharmaceutical, psychoactive agent, or psychotropic drug is a chemical substance that changes the function of the nervous system and results in alterations of perception, mood, cognition, and behavior. These substances may be used medically, recreationally, for spiritual reasons (for example, by altering one's consciousness, as with entheogens for ritual, spiritual, or shamanic purposes), or for research. Some categories of psychoactive drugs may be prescribed by physicians and other healthcare practitioners because of their therapeutic value. Some psychoactive substances may be used in detoxification and rehabilitation programs for people who may have become dependent upon or addicted to other mind-altering or mood-altering substances. Drug rehabilitation attempts to reduce addiction through a combination of strategies such as psychotherapy, support groups, and sometimes medication such as psychoactive substances. Psychoactive substances often bring various changes in consciousness and mood that the user may find rewarding and pleasant (e.g., euphoria or a sense of relaxation) or advantageous in an observable or measurable way (e.g., increased alertness). Substances that are rewarding and thus positively reinforcing have the potential to induce a state of addiction – compulsive drug use despite negative consequences. In addition, sustained use of some substances may produce physical or psychological dependence, or both, associated with somatic or psychological-emotional withdrawal states, respectively.Psychoactive drug misuse, dependence, and addiction have resulted in legal measures and moral debate. Governmental controls on manufacture, supply, and prescription attempt to reduce problematic medical drug use. Ethical concerns have also been raised about the overuse of these drugs clinically and about their marketing by manufacturers. Popular campaigns to decriminalize or legalize the recreational use of certain drugs (e.g., cannabis) are also ongoing. Source: Wikipedia (en)