Psilocin and psilocybin are tryptamines with psychedelic effects. In nature they always occur together, with psilocybin predominating. When psilocybin is ingested, it's metabolised to psilocin, which then acts on serotonin receptors in the brain. Psilocin is structurally similar to serotonin (5-HT) and has no significant effect on dopamine receptors. For this and other reasons psilocin is not an addictive substance and non-lethal.
Though occurring naturally in mushrooms throughout the world, psilocybin and psilocin are Schedule 1 drugs under the 1971 Convention of Psychotropic Substances, a treaty agreed upon by the United Nations. The Netherlands is the only country that permits the cultivation and sale of fungal products containing these compounds, provided they are not processed (i.e. extracted, dried etc.).
Psilocin's chemical name is 4-hydroxy-N,N-dimethyltryptamine, or simply 4-HO-DMT. As the name indicates, psilocin is related to the active compound of ayahuasca (N,N-DMT) and the secretions of the Bufo alvarius toad (5-MeO-DMT). Although it's psilocin that gives rise to the psychoactive effects, it is not as stable as psilocybin. Oxygen and heat will quickly degrade psilocin into ineffective compounds. Psilocin is so sensitive to oxygen, that when picking mushrooms, the stems quickly bruise bluish to dark black. For this reason research is usually conducted with synthetic psilocybin capsules rather than psilocin. Likewise the psilocybin/psilocin ratio in mushrooms is not of primary importance, although it does make a small difference when making mushroom tea or drying them.
Psilocybin's most common chemical name is O-phosphoryl-4-hydroxy-N,N-dimethyltryptamine. As the name indicates, it is psilocin with a phosphate group attached to it, making it a much more stable compound. In the liver a dephosphorylation reaction occurs, detaching the phosphate group, resulting in the psychoactive psilocin.
Psilocin is then further metabolised by the body's mono-amino oxidase enzyme into compounds that are non-toxic and can easily be excreted.
Psilocybin is about a hundred times less potent than LSD on a weight-by-weight basis, and the effects last about half as long (4 to 5 hours, rather than 8). Still, even experienced LSD users may be overwhelmed by the extremely vivid visual effects when they first try a high dose of psilocybin. Especially in the dark or with eyes closed, psilocybin (and DMT or ayahuasca) generates visions in extremely bright colors.
In 1957, American banker and ethnomycologist R. Gordon Wasson was the first westerner to attend a traditional mushroom ceremony in Mexico and experience the psychedelic effects of psilocybin. Shortly afterwards the Swiss chemist Albert Hofmann, who in 1938 had discovered LSD, was able to extract psilocybin from the Psilocybe mexicana mushroom, and developed a method to synthesize the drug. In the early sixties Hofmann's employer Sandoz marketed and sold pure psilocybin pills to physicians and clinicians worldwide for use in psychedelic psychotherapy. Each pill contained 2 milligrams.
In August 1960 Timothy Leary, at the time a lecturer in psychology at Harvard University, travelled to Mexico and ate psilocybin mushrooms for the first time, an experience that drastically altered the course of his life.
Upon his return from Mexico, Leary and his associates began a research program known as the Harvard Psilocybin Project, using the pills provided by Sandoz. Leary first ingested two pills, which he reported as a light but clearly above-threshold dose.
Leary et al. administered between 20 and 70 mg of psilocybin in their "Prisoner Rehabilitation" program, but settled on 30 mg as the standard dose. In a paper describing the experiment, Leary stated: "Forty-five percent of the entire inmate group clearly underwent a mystical, transcendent, death-rebirth experience. This figure should be modified, however. The results for running sessions improved so that 100% of our recent groups were undergoing transcendent experiences." (Leary 1969)
Many researchers and psychotherapists favoured LSD over psilocybin. Eventually both substances were banned internationally, and all research and therapy halted.
Eventually some countries did permit psychedelic research to be conducted again.
In 2006 Roland R. Griffiths and colleagues published a research paper, describing the results of administering a dosage of 30 mg per 70 kg body weight, in which they stated: "Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance."
A 2011 study by Griffiths et al suggests that taking a single high dosage of psilocybin can cause long-term changes in the personality of its users. Changes in personality were assessed using the Revised NEO Personality Inventory, which describes people's personalities according to five factors: neuroticism, extroversion, conscientiousness, agreeableness, and openness. In the study, about half of the participants — described as healthy, "spiritually active", and many possessing postgraduate degrees — showed an increase in the personality dimension of "openness", and this positive effect was apparent more than a year after the psilocybin session.