Albert Hofmann, the well-known chemist who discovered and experimented with LSD, was the first to recognize the importance and chemical structure of the pure compounds psilocybin and psilocin. Hofmann was aided in this process by his willingness to ingest extracts isolated from Psilocybe. Hofmann's colleagues at the University of Delaware were also trying to isolate the active principle, but were unsuccessful.
In 1961, Timothy Leary and Richard Alpert ran the Harvard Psilocybin Project, carrying out a number of experiments concerning the use of psilocybin in the treatment of personality disorders and other uses in psychological counselling.
A pilot study led by Francisco Moreno and supported by Multidisciplinary Association for Psychedelic Studies (MAPS) studied the effects of psilocybin on nine patients with obsessive-compulsive disorder. The study found that psilocybin could be safely given to patients with OCD but, due to the study design, it was unable to confirm or deny that psilocybin was effective in relieving obsessive compulsive disorder symptoms.
Two current studies are investigating the possibility that psilocybin can ease the psychological suffering associated with cancer. One study, led by Charles Grob, involves 12 subjects with terminal cancer being administered the hallucinogen or a placebo in two separate sessions. A second study, led by Roland Griffiths at Johns Hopkins, will administer psilocybin on two occasions to people "with a current or past diagnosis of cancer who have some anxiety or are feeling down about their cancer".
The effects of psilocybin are highly variable, and dependent on the current mood and overall sense of well-being by the individual. Initially the subject may begin to feel somewhat disorientated, lethargic, and euphoric or sometimes depressed. At low doses, hallucinatory effects may occur, including enhancement of colors and the animation of geometric shapes. Closed-eye visuals may occur, where the affected individual may see multi-coloured geometric shapes and vivid imaginative sequences. At higher doses, hallucinatory effects increase and experiences tend to be less social and more introspectic or entheogenic. Open-eye visuals are more common, and may be very detailed although rarely confused with reality.
Users having a pleasant experience may feel ecstatic, including a deep sense of connection to others, confusion, hilarity, and a general feeling of connection to nature and the universe. Difficult experiences or bad trips may occur in some individuals, often when consumed during emotional turmoil, in a non-supportive or inadequate environment, by an inexperienced person, or in an unexpectedly high dose (see: set and setting). Latent psychological issues may be triggered by the strong emotional components of the experience.
Some of these individuals report that they have experienced a 'spiritual' episode. For example, in the Marsh Chapel Experiment, which was run by a graduate student at Harvard Divinity School under the supervision of Timothy Leary, almost all of the graduate degree divinity student volunteers who received psilocybin reported profound religious experiences. A brief video about the Marsh Chapel experiment can be viewed here
In 2006, a group of researchers from Johns Hopkins School of Medicine led by Roland R Griffiths conducted an experiment assessing the degree of mystical experience and attitudinal effects of the psilocybin experience; this report was published in the journal Psychopharmacology. Thirty-six volunteers without prior experience with hallucinogens were given psilocybin and methylphenidate (Ritalin) in separate sessions, the methylphenidate sessions serving as a control and psychoactive placebo; the tests were double-blind. The degree of mystical experience was measured using a questionnaire on mystical experience developed by Ralph W Hood; 61% of subjects reported a "complete mystical experience" after their psilocybin session, while only 13% reported such an outcome after their experience with methylphenidate. Two months after taking psilocybin, 79% of the participants reported moderately to greatly increased life satisfaction and sense of well-being. About 36% of participants also had a strong to extreme “experience of fear” or dysphoria (i.e., a “bad trip”) at some point during the psilocybin session (which was not reported by any subject during the methylphenidate session), with about one-third of these (13% of the total) reporting that this dysphoria dominated the entire session. These negative effects were reported to be easily managed by the researchers and did not have a lasting negative effect on the subject’s sense of well-being. Further measures at 14 months after the psilocybin experience confirmed that participants continued to attribute deep personal meaning to the experience. This research was widely covered in the major media outlets. The research team cautions that if hallucinogens are used in less well supervised settings, the possible fear or anxiety responses could lead to harmful behaviors. Further studies by this group are investigating the relationship of psilocybin dose to likelihood of mystical experience in healthy volunteers and whether mystical experiences in volunteers given psilocybin can help with anxiety and poor mood due to cancer.
A very small number of people are unusually sensitive to psilocybin's effects, where a normally threshold dose of around 2 mg of psilocybin can result in effects usually associated with medium and high doses. Likewise, there are some people who require relatively high doses of psilocybin to gain low-dose effects. Individual brain chemistry and metabolism plays a large role in determining a person's response to psilocybin.
Psilocybin is metabolized mostly in the liver where it becomes psilocin. It is broken down by the enzyme monoamine oxidase. MAO inhibitors have been known to sustain the effects of psilocybin for longer periods of time; people who are taking an MAOI for a medical condition or are seeking to potentiate the mushroom experience may experience highly potentiated effects.
Mental and physical tolerance to psilocybin builds and dissipates quickly. Taking psilocybin more than three or four times in a week (especially on consecutive days) can result in diminished effects. Tolerance dissipates after a few days, so frequent users often keep doses spaced five to seven days apart to avoid the effect.
In rare cases, psilocybin use can cause Hallucinogen Persisting Perception Disorder.
Possession and use of psilocybin mushrooms, including the bluing species of Psilocybe, is therefore prohibited by extension. However, in many national, state, and provincial drug laws, there is a great deal of ambiguity about the legal status of psilocybin mushrooms and the spores of these mushrooms, as well as a strong element of selective enforcement in some places. For more details on the legal status of psilocybin mushrooms and Psilocybe spores, see: Psilocybe: Social and legal aspects.
Because of the ease of cultivating psilocybin mushrooms or gathering wild species, purified psilocybin is often extremely difficult to find on the market.