Ancient and/or historic evidence of cerebral mycetisms induced by the accidental ingestion of hallucinogenic mushrooms has been documented in various parts of the world. Early reports of intoxication attributed to the unintentional consumption of these fungi come from China as early as the 3rd century A.D., Japan during the eleventh century A.D., Great Britain in both l799 and in the early l800's, in the United States around the early l900's and in France in the early l960's.

It is of interest to note that a report from Japan indicated that there were over 366 accidental ingestions of psilocybin mushrooms reported in l929; these incidents were reported by people foraging for wild edible mushrooms.

In Africa during the l940's a number of unintentional intoxications occurred when mind-altering mushrooms were inadvertently sold as a source of food by children in public markets.

It must be noted that outside of a few intoxications caused by Psilocybe cubensis (in Africa), and one caused by Psilocybe semilanceata (in England in the late 1700's), the majority of all intoxications which occurred prior to the recreational use of these species, were caused by various species of Panaeolus with the exception of Japan and the Northeastern United States, where some of the inebriations were the result of ingesting various species of both Gymnopilus and Panaeolus species.

Published reports describing symptoms attributed to Panaeolus intoxications, were often written in a similar manner. Subjective effects included:

"...drowsiness, lightheadedness, an inability to walk, a staggering gait, giggliness, much hilarity, inappropriate speech, uncontrollable laughter, euphoria and acting as if one were on a bender." On the other hand, occasionally terrifying, visual and psychological disturbances have been known to result from accidental or deliberate ingestion of Psilocybe cubensis and P. semilanceata, which sometimes resulted in emergency room treatment.

In a paper published in 1958, Dr. Sam Stein briefly mentioned similar observations when Panaeolus and Psilocybe fungi were used in the treatment of a single patient. Mushroom extracts used by Dr. Stein were obtained from dried specimens of Panaeolus venenosus (=Panaeolus subbalteatus), and Psilocybe caerulescens. Further investigations were carried out in 1959 by Stein and some of his colleagues who revealed that the subjective effects caused by the ingestion of Panaeolus species were more tranquil and less hallucinogenic than the effects produced by the ingestion of certain species of Psilocybe.

The fear of poisoning by physically toxic mushrooms is the main cause of mycophobia (a fear of mushrooms) throughout the world. Many of the deadly poisonous species of mushrooms macroscopically resemble some of the hallucinogenic mushrooms in the genus Psilocybe. For example, three species of deadly poisonous Galerina's, and Conocybe filaris, which are extremely poisonous mushrooms, are commonly found in mulched gardens in the Pacific Northwest of the United States and other regions of the world, and have been observed sharing the same habitat as Psilocybe baeocystis, Psilocybe cyanescens, and Psilocybe stuntzii (for example, see the above photographs of both Psilocybe stuntzii and Psilocybe cyanescens pictured together with some members of the deadly Galerina family.

Another example of misidentification involves Chlorophyllum molybdites, a species commonly referred to as "green gills" or "Morgans" Lepiota. As the nick-name implies, the gills of this species are green. This occurs with age. This mushroom is rather large with a scaly cap which resembles a parasol. This species is common in manured fields, meadows and lawns and does not grow directly in manure but may be found in manured fields where cattle and water buffalo graze.

According to Stephen Peele, curator of the Florida Mycology Research Center, it is often picked and accidentally consumed in Florida; usually mistaken for Psilocybe cubensis (personal communication to J.W. Allen). Chlorophyllum molybdites is considered toxic but not deadly.

Peele also claimed that in Tampa, Florida, over 90% of all mushroom poisonings were the result of accidentally consuming specimens of C. molybdites which were mistaken for Psilocybe cubensis.

While two children in California developed a "mydriasis-fever-convulsions" syndrome after ingesting mushrooms taken from a lawn habitat, another in the state of Washington was reported to have died due to complications following the suspected consumption of hallucinogenic mushrooms. Also, three children were reportedly mildly poisoned after accidentally grazing on lawn specimens of Panaeolina foenisecii (a non-hallucinogenic mushroom). Later investigations of Panaeolina foenisecii by Allen and Merlin (1992b), reported that this species is not psychoactive.

A sixteen year old girl from Whidbey Island, Washington did die in December l981 after accidentally picking and eating several fresh specimens of Galerina autumnalis. She and her two teenage male companions had assumed that they ingested Psilocybe mushrooms.

It is thus possible that young children may be susceptible to convulsions following the consumption of some varieties of psilocybian mushrooms. However, the world renown Mazatec curandera María Sabina and her sister María Ana, made famous by the writings of the Wassons' and others, both first ate these hallucinogenic mushrooms somewhere between the ages of 7-9, and María Sabina continued to do so for over 70 years without any apparent physical illness. Also, R. Gordon Wasson and his wife Valentina, allowed their 19-year-old daughter Masha to eat mushrooms apparently without ill effect.

Even a professional mycologist must be quite careful when deciding which wild mushrooms may be safe for human consumption. For example, some mushrooms, which are common and edible in Europe, can be deadly poisonous or harmful enough to cause physical damage when collected and consumed in the United States, Canada, or even Australia. In 1978, Jonathan Ott reported that the "Ld50 (lethal dosage) in mice for psilocybin has been determined to be 280 mg/kg, oral ingestion", thereby assuming that a person of average weight (i.e. 70 kg/155 lb) person, "would have to ingest l9.6 grams of [the extracted chemical] psilocybin to produce death." However, in 1989, Dr. Karl L. R. Jansen at the University of Auckland stated that he believes that "the LD50 (the dose at which 50% of a sample will die) has been determined as 280 mg/kg in mice. However, it is not valid to calculate the LD50 for humans by a simple percentage/weight calculation. Mice and humans have very different metabolic rates and dispose of drugs in different ways. It is unlikely that even a large number of psilocybine mushrooms would not be toxic in humans, but we cannot suggest an exact figure from data based on rodent studies."