Hallucinogens are a class of psychoactive substances that act on the nervous system to alter perception, mood, and various cognitive processes. Hallucinogens represent one of the three major classes of psychoactive substances: the other two are stimulants ("uppers") and depressants ("downers"). Unlike stimulants or depressants, however, hallucinogens are claimed to neither merely amplify or dull existing states of consciousness, but instead produce qualitatively different ones in which the environment and self are perceived in a new fashion.
Hallucinogens are divided into three categories: psychedelics (LSD, psilocybin mushrooms, DMT, etc.), dissociatives (ketamine, PCP, DXM, etc.), and deliriants (includes DPH, scopolamine, datura, etc).
Notably, hallucinogens are commonly reported to facilitate self-understanding and self-discovery. Hallucinogenic experiences are often compared to non-ordinary forms of consciousness such as lucid dreaming, meditation, religious, mystical or transpersonal experiences, hallucinations, dreams and states of psychosis.
List of hallucinogens