hallucinogen

A hallucinogen is a substance that causes significant alterations in perception, mood, and cognition. Effects can include visual or auditory distortions, time distortion, synesthesia, and changes in sense of self. The experience is influenced by dose, environment, and individual psychology, a concept often summarized as set and setting.

Hallucinogens are usually categorized into several groups. Classical psychedelics such as lysergic acid diethylamide (LSD), psilocybin (magic mushrooms), and mescaline produce profound perceptual changes and are thought to primarily act via serotonin receptors, especially 5-HT2A. Dissociatives such as ketamine and phencyclidine (PCP) can detach perception from body and environment and often act on NMDA receptors. Deliriants, including tropane alkaloids found in plants like datura, cause confusion and delirium with less vivid visual effects.

In clinical research, psychedelics are studied for potential therapeutic uses, including treatment of depression, anxiety, post-traumatic stress disorder, and addiction, when administered in controlled settings with professional guidance. However, many hallucinogens carry risks such as acute anxiety or paranoia, dangerous behavior during intoxication, and the emergence of latent psychiatric illness in susceptible individuals. Physiological toxicity is generally low for many classic psychedelics, but interactions with other drugs or medical conditions can be hazardous.

Legal status varies by country and substance; some are controlled substances, while research programs operate under regulatory approvals. The term hallucinogen denotes a broad category, distinct from stimulants or depressants, and covers substances with diverse pharmacology and effects.