Hallucinogenic << huh `LOO` suh nuh JEHN ihk >> drug is any of several substances that distort perception of oneself and one’s surroundings. These drugs temporarily change the chemistry of the brain. Hallucinogenic drugs affect the senses, emotions, and reasoning, and the brain’s control of muscles and certain body functions. The changes may be extremely pleasant or highly unpleasant and frightening. In the United States, laws prohibit the manufacture, distribution, and possession of these drugs, except for government-approved research and certain Native American religious rituals.
The effects of hallucinogenic drugs are sometimes called trips. During a trip, a drug user may see bright, moving colors. The user may hallucinate (see or hear things that are not present). The size, shape, or color of objects may appear to change constantly. In some cases, the user may do something reckless, not realizing the danger of being hurt or even killed. The user may have a sense of overwhelming fear, sadness, and horror or may feel intense love and joy.
The experience and effect of each trip can be influenced by (1) the type and amount of drug taken, (2) the circumstances in which the drug is used, and (3) the user’s personality and mood. The effects of hallucinogenic drugs last from one hour to several days. But these effects may appear again months later as a flashback. Some people who repeatedly use hallucinogenic drugs experience long-lasting disturbances in perception. This condition, called hallucinogen persisting perception disorder, can last for months after discontinuing use of the drug.
Hallucinogenic drugs include naturally occurring drugs, such as mescaline, and manufactured substances, such as LSD (short for lysergic acid diethylamide) and Ecstasy. Mescaline is produced by the peyote cactus. Taking mescaline may cause users to see beautiful color patterns or frightening visions of themselves and others as monsters. LSD produces similar effects, but it is far more powerful than mescaline, requiring only 100 millionths of a gram to produce a trip. 
Mescaline and LSD are often called psychedelic (mind-revealing) drugs. These drugs may give users the feeling that they are gaining new insights into their personality and past experiences. The drugs also may make individuals anxious, confused, or terrified. Scientists do not consider psychedelic drugs to be addictive. But some users may develop a psychological dependence on them.
Ecstasy has both hallucinogenic and stimulant properties. Stimulants increase certain activities of the nervous system. Ecstasy is also called MDMA, an abbreviation of its chemical name, 3,4 methylenedioxymethamphetamine. Ecstasy is known as a “club drug” because it is often used at nightclubs and dance parties.
Some experts classify dissociative drugs as hallucinogenic drugs. Dissociative drugs produce a generalized “numbing” or dreamlike effect. Dissociative drugs can have unpredictable effects in some users, including aggression, paranoia, delirium, seizures, or coma. Dissociative drugs include ketamine and PCP (phencyclidine), both developed in the mid-1900’s as anesthetic drugs. Their hallucinogenic and dissociative effects were discovered later. Another dissociative drug, dextromethorphan (DXM), is found in some cough and cold medications. It is a cough suppressant at normal doses. But when taken in very high doses, it can have dissociative effects. Some people who misuse dissociative drugs become addicted to them.
