Hallucinogens are drugs that distort a person’s perception of sight and sound, along with their thinking processes and feelings. They are broadly classified as either classic hallucinogens (e.g., LSD, Psilocybin) or dissociative drugs (e.g., Ketamine, DXM). While both can cause hallucinations, dissociative drugs are also typified by feelings of detachment (or dissociation) from oneself or one’s environment.

Most hallucinogens are Schedule I controlled substances--meaning that they are illegal to use, have no medicinal value, and have high potential for abuse or dependency—with notable exceptions in Ketamine (Schedule III) and PCP (Schedule II). (You still can't walk into CVS with a Ketamine script,though--Ketamine is used as an intravenous anesthetic.)

How do hallucinogens work?

More research needs to be done to fully understand how hallucinogens affect the brain and body.

The limited existing research suggests that classic hallucinogens disrupt communication between brain chemical systems throughout the nervous system. Some hallucinogens also seem to interfere with the serotonin, the chemical partially responsible for mood and feelings of happiness.

Dissociative drugs interfere with the action of glutamate, a neurological chemical that regulates pain perception, emotion, and memory.