Hallucinogenic compounds in the form of, or extracted from, plants and mushrooms have been used for centuries, mostly in religious rituals. Almost all hallucinogens contain nitrogen and are classified as alkaloids. Many hallucinogens have chemical structures similar to those of neurotransmitters (e.g., acetylcholine-, serotonin-, or catecholamine-like) and temporarily interfere with their action or bind their receptor sites, but the exact mechanisms by which these substances exert their hallucinogenic effects remain unclear. This InfoFacts will discuss four common types of hallucinogens:

How are Hallucinogens Abused?

The very same characteristics that led to the incorporation of hallucinogens into ritualistic or spiritual traditions have also led to their propagation as drugs of abuse. Importantly, and unlike most other drugs, the effects of hallucinogens are highly variable and characteristically unreliable, producing different effects in different people or at different times. This is mainly due to the significant variations in amount and composition of active compounds, particularly in the hallucinogens derived from plants and mushrooms. Because of their unpredictable nature, the use of hallucinogens can be particularly dangerous.

How do Hallucinogens Affect the Brain?

LSD, peyote, psilocybin, and PCP are drugs that cause hallucinations, which are profound distortions in a person’s perception of reality. Under the influence of hallucinogens, people see images, hear sounds, and feel sensations that seem real but do not exist. Some hallucinogens also produce rapid, intense emotional swings. LSD, peyote, and psilocybin cause their effects by initially disrupting the interaction of nerve cells and the neurotransmitter serotonin.1 Distributed throughout the brain and spinal cord, the serotonin system is involved in the control of behavioral, perceptual, and regulatory systems, including mood, hunger, body temperature, sexual behavior, muscle control, and sensory perception. PCP, on the other hand, acts mainly through a type of glutamate receptor in the brain, important for the perception of pain, responses to the environment, and memory.

There have been no properly controlled research studies on the specific effects of these drugs on the human brain, but smaller studies and several case reports have been published documenting some of the effects associated with the use of hallucinogens: