Are there long-term effects of taking hallucinogenic mushrooms?

There are no long term physical effects from ingestion of mushrooms containing psilocybin and psilocin. As far as long term mental effects go this is a subject for debate and has no clear cut answer based on the little bit of research and clinical studies that have been done. This thread has a good conversation on this subject.

Negative long term mental effects from extended high dosages may include some cognitive impairment and HPPD (Hallucinogen Persisting Perceptual Disorder) and possibly some emotional liability due to effects on serotonin levels produced by the human brain. Usually temporary, these fade with cessation of use over a period of a few months.

Postive long term mental effects from any dosage amount may include a personal conviction of philosophical or religious enlightenment, a stronger sense of one's identity, and a feeling of intimacy with all of life including nature (plants, trees, animals, etc).

Studies have shown that over years of occasional use, the user notices no apparent change in his/her physical or mental condition that would be considered detrimental. In fact, many users state the opposite. However, it is possible, as with any noteworthy experience in life, that if a user were to have a tough time while under the influence of the mushroom that they could have an ongoing spiritual or psychological issue to sort out. The odds of somoeone having a long-term "issue," though, as a result of the mushroom experience, is probably exceedingly rare based on all the personal accounts we are able to read about.

Research:
"Psilocybin affects core dimensions of altered states of consciousness and physiological parameters in a dose-dependent manner. Our study provided no cause for concern that Psilocybin is hazardous with respect to somatic health" - Acute psychological and physiological effects of psilocybin in healthy humans: a double-blind, placebo-controlled dose-effect study; Hasler F , Grimberg U, Benz MA, Huber T, Vollenweider FX <#>

"This drug is not associated with physical or psychological dependency, acute toxicity is largely limited to possible panic and anxiety attacks and, in terms of chronic toxicity, the worst that can happen are flashbacks. Consequently, the use of paddos (hallucinogenic mushrooms) does not, on balance, present any risk to the health of the individual" - Risk Assessment by CAM (Coordination Centre for the Assessment and Monitoring of New Drugs), 2000. <#>