A class of drugs reliably inducing temporary states of altered perception, often with symptoms similar to those of psychosis. The drug experiences are clearly perceived, vivid, and remembered. Sensory input is heightened and subjective experience is intensified, but control is diminished. The subject's feelings and momentary perceptions gain an independence from the normal corrections of logic; whatever stray item occupies the attention (a sensation or an unguarded and unevaluated memory or thought) becomes at the moment compellingly significant. Thinking and perceiving of this order coexist with the capacity for, but not an interest in, normal thought and function.
These drugs have been called psychedelic (or mind-manifesting) because of the convincing clarity with which a normally suppressed, more sensory, plastic, and primitive part of the mind is revealed to the drugged subject, contrasting sharply with the capacity to focus, discriminate, and judge.
The two drugs of chief interest, mescaline and LSD-25 (lysergic acid diethylamide), are of ancient lineage. Mescaline, used in highly structured Amerindian tribal religious rituals, is derived from peyote buttons, which are the dried tops of a cactus found in the southwestern United States. LSD has been synthesized with compounds derived from ergot, which infests such grasses as rye. (Some ergot derivatives are useful in the treatment of migraine and in obstetrics for the postpartum constriction of the uterus and blood vessels.)
There are a number of other psychotomimetics (less potent than LSD but similar), such as those from mushrooms (psilocybin and psilocin) and those synthesized in the laboratory. Ring-substituted amphetamines resembling mescaline's structure (for example, “STP”) have been produced in profusion. There are subtle differences among these newer compounds, some producing more or less euphoria and more or less dyscontrol and anxiety.
