Psilocybin - Occurrence

Occurrence

P. semilanceata is common in Europe, Canada, and the United States.

Psilocybin is present in varying concentrations in over 200 species of Basidiomycota mushrooms. In a 2000 review on the worldwide distribution of hallucinogenic mushrooms, Gastón Guzmán and colleagues considered these to be distributed amongst the following genera: Psilocybe (116 species), Gymnopilus (14), Panaeolus (13), Copelandia (12), Hypholoma (6), Pluteus (6) Inocybe (6), Conocybe (4), Panaeolina (4), Gerronema (2) and Agrocybe, Galerina and Mycena (1 species each). Guzmán increased his estimate of the number of psilocybin-containing Psilocybe to 144 species in a 2005 review. The majority of these are found in Mexico (53 species), with the remainder distributed in the US and Canada (22), Europe (16), Asia (15), Africa (4), and Australia and associated islands (19). In general, psilocybin-containing species are dark-spored, gilled mushrooms that grow in meadows and woods of the subtropics and tropics, usually in soils rich in humus and plant debris. Psilocybin mushrooms occur on all continents, but the majority of species are found in subtropical humid forests. Psilocybe species commonly found in the tropics include P. cubensis and P. subcubensis. P. semilanceata—considered by Guzmán to be the world's most widely distributed psilocybin mushroom—is found in Europe, North America, Asia, South America, Australia and New Zealand, but is entirely absent from Mexico. Although the presence or absence of psilocybin is not of much use as a chemotaxonomical marker at the familial level or higher, it is used to classify taxa of lower taxonomic groups.

Species	% psilocybin
P. azurescens	1.78
P. serbica	1.34
P. semilanceata	0.98
P. baeocystis	0.85
P. cyanescens	0.85
P. tampanensis	0.68
P. cubensis	0.63
P. weilii	0.61
P. hoogshagenii	0.60
P. stuntzii	0.36
P. cyanofibrillosa	0.21
P. liniformans	0.16
Maximum reported psilocybin concentrations (% dry weight) in 12 Psilocybe species

Both the caps and the stems contain the psychoactive compounds, although the caps contain consistently more. The spores of these mushrooms do not contain psilocybin or psilocin. The total potency varies greatly between species and even between specimens of a species collected or grown from the same strain. Because most psilocybin biosynthesis occurs early in the formation of fruit bodies or sclerotia, younger, smaller mushrooms tend to have a higher concentration of the drug than larger, mature mushrooms. In general, the psilocybin content of mushrooms is quite variable (ranging from almost nothing to 1.5% of the dry weight) and depends on species, strain, growth and drying conditions, and mushroom size. Cultivated mushrooms have less variability in psilocybin content than wild mushrooms. The drug is more stable in dried than fresh mushrooms; dried mushrooms retain their potency for months or even years, while mushrooms stored fresh for four weeks contain only traces of the original psilocybin. The psilocybin contents of dried herbarium specimens of Psilocybe semilanceata in one study were shown to decrease with the increasing age of the sample: collections dated 11, 33, or 118 years old contained 0.84%, 0.67%, and 0.014% (all dry weight), respectively. Mature mycelia contain some psilocybin, while young mycelia (recently germinated from spores) lack appreciable amounts. Many species of mushrooms containing psilocybin also contain lesser amounts of the analog compounds baeocystin and norbaeocystin, chemicals thought to be biogenic precursors. Most species of psilocybin-containing mushrooms bruise blue when handled or damaged due to the oxidization of phenolic compounds. This reaction, however, is not a definitive method of identification or determining a mushroom's potency.