Long-term use was associated with thinning of the posterior cingulate cortex , thickening of the anterior cingulate cortex , and decreased neocortical 5-HT2A receptor binding .
Despite the high method ological heterogeneity and the small sample sizes , the results suggest that hallucinogens increase introspection and positive mood by modulating brain activity in the fronto-temporo-parieto-occipital cortex
Serotonergic hallucinogens produce alterations of perceptions , mood , and cognition , and have anxiolytic , antidepressant , and antiaddictive properties .
These drugs act as agonists of frontocortical 5-HT2A receptors , but the neural basis of their effects are not well understood .
Thus , we conducted a systematic review of neuroimaging studies analyzing the effects of serotonergic hallucinogens in man .
Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance
Rationale Although psilocybin has been used for centuries for religious purpose s , little is known scientifically about its acute and persisting effects . Objectives This double-blind study evaluated the acute and longer-term psychological effects of a high dose of psilocybin relative to a comparison compound administered under comfortable , supportive conditions . Material s and methods The participants were hallucinogen-naïve adults reporting regular participation in religious or spiritual activities . Two or three sessions were conducted at 2-month intervals . Thirty volunteers received orally administered psilocybin ( 30 mg/70 kg ) and methylpheni date hydrochloride ( 40 mg/70 kg ) in counterbalanced order . To obscure the study design , six additional volunteers received methylpheni date in the first two sessions and unblinded psilocybin in a third session . The 8-h sessions were conducted individually . Volunteers were encouraged to close their eyes and direct their attention inward . Study monitors rated volunteers ’ behavior during sessions . Volunteers completed question naires assessing drug effects and mystical experience immediately after and 2 months after sessions . Community observers rated changes in the volunteer ’s attitudes and behavior . Results Psilocybin produced a range of acute perceptual changes , subjective experiences , and labile moods including anxiety .  Psilocybin also increased measures of mystical experience . At 2 months , the volunteers rated the psilocybin experience as having substantial personal meaning and spiritual significance and attributed to the experience sustained positive changes in attitudes and behavior consistent with changes rated by community observers . Conclusions When administered under supportive conditions , psilocybin occasioned experiences similar to spontaneously occurring mystical experiences . The ability to occasion such experiences prospect ively will allow rigorous scientific investigations of their causes and consequences
Long-term use was associated with thinning of the posterior cingulate cortex , thickening of the anterior cingulate cortex , and decreased neocortical 5-HT2A receptor binding .
Despite the high method ological heterogeneity and the small sample sizes , the results suggest that hallucinogens increase introspection and positive mood by modulating brain activity in the fronto-temporo-parieto-occipital cortex
Serotonergic hallucinogens produce alterations of perceptions , mood , and cognition , and have anxiolytic , antidepressant , and antiaddictive properties .
These drugs act as agonists of frontocortical 5-HT2A receptors , but the neural basis of their effects are not well understood .
Thus , we conducted a systematic review of neuroimaging studies analyzing the effects of serotonergic hallucinogens in man .