Psilocybe semilanceata is the classic example of a magic mushroom, but there are quite a few others. These fungi also have some species with psilocybin: Copelandia, Gymnopilus, Inocybe, Mycena, Panaeolus, Pholiotina, Pluteus.
Psilocybin can kill in extremely high doses. The LD50 of psilocybin is 280 mg/kg for rats, this is about 1.5 times that of caffeine. In normal psychedelic mushrooms, psilocybin makes up about 1% of their weight. Therefore, nearly 1.7 kilograms of dried mushrooms, or 17 kilograms of fresh mushrooms, would be required for a 60 kg person to reach the 280 mg/kg LD50 rate of rats.
Psilocybin mushrooms have probably been used since prehistoric times. They may be seen in rock art.[5] Many cultures have used these mushrooms in religious rites. Psychedelic mushrooms have been used by native peoples of Mesoamerica for religious communion and healing. Catholicmissionaries were against the use of magic mushrooms. In Modernsociety, they are sometimes used recreationally. Their medical use in psilocybin-assisted psychotherapy is studied,[6][7] for example, in the treatment for anxiety and depression in patients with life-threatening cancer,[8] the treatment of depression[9][10] and to help quit smoking.[11]
The function of compounds like this in nature is they reduce the likelihood of the mushroom being eaten before its spores have been scattered. It is a defence against herbivory.
