Psychopharmacology, study of the relationship between drugs and brain function, including mood, perceptions, and behavior. Psychopharmacology is a branch of pharmacology, the study of the action of drugs on living organisms. Psychopharmacology is employed in psychiatry, psychology, neurology, and in medical specialties concerned with brain function.
Throughout history, almost every culture has sought ways to alter consciousness by experimenting with plant substances that yield many of the psychoactive drugs of today. Important developments in ancient psychopharmacology include the discovery and use of alcohol, cannabis, and opium in Europe and Asia and of caffeine, nicotine, cocaine, and hallucinogenic plants such as peyote and psilocybin in the pre-Columbian Americas. Developments in the 19th century include the isolation of the potent analgesic morphine from opium; the introduction of the anesthetics nitrous oxide, ether, and chloroform; and the early use of cocaine as a stimulant. The first sedative hypnotics, the barbiturates (see Barbiturate), were introduced in the early 20th century, followed by the discovery and use of amphetamines (see Epinephrine) as psychostimulants in the 1930s; the discovery of the hallucinogenic properties of lysergic acid diethylamide in 1943; the discovery of lithium carbonate as a treatment for manic-depression in 1948; the discovery of the antipsychotic, antischizophrenic activity of chlorpromazine in 1952; and the discovery, in 1957, of two treatments for depression: tricyclic antidepressants and monoamine oxidase (MAO) inhibitors. In the latter 20th century many drugs continue to be found that fall within these major groupings. Also included among the psychoactive agents are the so-called minor tranquilizers, the benzodiazepines.