A large and scattered body of clinical and research reports on daydreaming, sleep and dreams, hypnosis, sensory deprivation, dissociative and depersonalization states, and drug-induced mental changes has not been organized into a consistent theoretical framework. This work aims to integrate current knowledge about various altered states of consciousness to determine the conditions necessary for their emergence, the factors influencing their outward manifestations, their common denominators, and the adaptive or maladaptive functions they may serve.
Hallucinogenic substances such as LSD, psilocybin, and psilocin are far more potent than older agents like peyote and mescaline. Renewed interest in these drugs has led to speculation about their applications across diverse fields, including anthropology, where their socially sanctioned use in some cultures is described; fiction, where their role in utopian societies is imagined; and medicine, where they have been proposed for treating mental illness or inducing model psychoses. Others have suggested their use as educational tools or for triggering religious mystical experiences.