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A psychoactive drug, psychopharmaceutical, or psychotropic is a chemical substance that changes brain function and results in alterations in perception, mood, or consciousness. These substances may be used recreationally, to purposefully alter one's consciousness, or as entheogens, for ritual, spiritual, or shamanic purposes, as a tool for studying or augmenting the mind. Some categories of psychoactive drugs, which are prescription medicines, have medical therapeutic utility, such as anesthetics, analgesics, hormonal preparations, anticonvulsant and antiparkinsonian drugs or for the treatment of neuro-psychiatric disorders, as hypnotic drugs, anxiolytic and some stimulant medications used in ADHD and some sleep disorders. There are also some psychoactive substances used in the detoxification and rehabilitation programs for psychoactive drug users. Psychoactive substances often bring about subjective (although these may be objectively observed) changes in consciousness and mood that the user may find rewarding and pleasant (e.g. euphoria) or advantageous (e.g. increased alertness) and are thus reinforcing. Substances which are both rewarding and positively reinforcing have the potential to induce a state of addiction – compulsive drug use despite negative consequences – when used consistently in excess. In addition, sustained use of some substances may produce a physical dependence or psychological dependence syndrome associated with somatic or psychological-emotional withdrawal states respectively. Drug rehabilitation aims to break this cycle of dependency, through a combination of psychotherapy, support groups, maintenance and even other psychoactive substances. However, the reverse is also true in some cases, that 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''). "Psychedelic amphetamines" or empathogen-entactogens (such as MDA and MDMA) may produce an additional stimulant or euphoriant effect, and thus have an addiction potential. In part because of this potential for substance misuse, addiction, or dependence, the ethics of drug use is debated. Restrictions on drug production and sales in an attempt to decrease drug abuse is very common among national and sub-national governments worldwide. Ethical concerns have also been raised about over-use of these drugs clinically, and about their marketing by manufacturers. == History == Psychoactive drug use can be traced to prehistory. There is archaeological evidence of the use of psychoactive substances (mostly plants) dating back at least 10,000 years, and historical evidence of cultural use over the past 5,000 years. The chewing of coca leaves, for example, dates back over 8000 years ago in Peruvian society.〔Early Holocene coca chewing in northern Peru Volume: 84 Number: 326 Page: 939–953〕 Medicinal use is one important facet of psychoactive drug usage. However, some have postulated that the urge to alter one's consciousness is as primary as the drive to satiate thirst, hunger or sexual desire. Supporters of this belief contend that the history of drug use and even children's desire for spinning, swinging, or sliding indicate that the drive to alter one's state of mind is universal. One of the first people to articulate this point of view, set aside from a medicinal context, was American author Fitz Hugh Ludlow (1836–1870) in his book ''The Hasheesh Eater'' (1857): 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. Animals and psychoactive plants appear to have co-evolved, possibly explaining why these chemicals and their receptors exist within the nervous system.〔(【引用サイトリンク】 title=Event Horizons of the Psyche )〕 During the 20th century, many governments across the world initially responded to the use of recreational drugs by banning them and making their use, supply, or trade a criminal offense. A notable example of this was Prohibition in the United States, where alcohol was made illegal for 13 years. However, many governments, government officials and persons in law enforcement have concluded that illicit drug use cannot be sufficiently stopped through criminalization. Organizations such as Law Enforcement Against Prohibition (LEAP) have come to such a conclusion, believing: 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 adequate factual information readily available, and that the negative effects of their use be minimized. Such is the case of Portuguese drug policy of decriminalization, which achieved its primary goal of reducing the adverse health effects of drug abuse.〔(【引用サイトリンク】title=5 Years After: Portugal's Drug Decriminalization Policy Shows Positive Results )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Psychoactive drug」の詳細全文を読む スポンサード リンク
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