The term "psychoactive" describes a substance that affects the central nervous system (the brain and spinal cord), producing changes in a person's mental activity and/or behavior. Psychoactive drugs may affect the way an individual thinks, behaves, and perceives or experiences his or her environment.

Many popular and widely used substances are psychoactive. These include alcohol, nicotine (tobacco), and caffeine. Dangerous psychoactive drugs that have little or no medical benefit include heroin, hallucinogens, and some older sedative-hypnotics such as methaqualone. Marijuana has traditionally been placed in this category. However, recent research has shown that marijuana may have some medical benefits in the treatment of glaucoma (an eye disease), nausea, and weight loss associated with cancer or AIDS.

Doctors prescribe psychoactive drugs for many reasons. Among the most important medical uses are as anesthesia for surgery and as analgesics (painkillers). Psychoactive drugs are also drugs of abuse when they are used for nonmedical purposes. These purposes include altering consciousness, improving performance, and improving mood. Some psychoactive substances, such as alcohol and peyote, are used as part of cultural and religious rituals.

Some psychoactive drugs produce an effect in people who suffer from a mental or medical disorder, but produce no effect on normal individuals. Antidepressant drugs, for example, will not affect a person's mood unless he or she is suffering from depression. Other psychoactive drugs, such as the sedative-hypnotics, produce similar effects in all individuals.

Psychoactive drugs are used to treat movement disorders, such as Parkinson's disease, and mental illnesses such as anxiety disorders, depression, bipolar disorder (also known as manic-depression), and schizophrenia. In addition, psychoactive drugs used to treat disorders in other parts of the body, such as high blood pressure, arrhythmia (irregular heartbeat), and inflammation, can also affect the central nervous system. In these cases, the psychoactive effects of these drugs are generally considered side effects.

See Also

Alcohol: Chemistry; Hallucinogens; Heroin; Marijuana; Sedative and Sedative-Hypnotic Drugs.