Effects

The effects of psilocybin mushrooms come from psilocybin and psilocin. They create short-term increases in tolerance of users, thus making it difficult to abuse them because the more often they are taken within a short period of time, the weaker the resultant effects are. Poisonous (sometimes lethal) wild picked mushrooms can be easily mistaken for psilocybin mushrooms. When psilocybin is ingested, it is broken down to produce psilocin, which is responsible for the psychedelic effects.
As with many psychedelic substances, the effects of psychedelic mushrooms are subjective and can vary considerably among individual users. The mind-altering effects of psilocybin-containing mushrooms typically last anywhere from 3 to 8 hours depending on dosage, preparation method, and personal metabolism. However, the effects can seem to last much longer to the user because of psilocybin's ability to alter time perception.
Some users suffer from hallucinogen persisting perception disorder, although this is uncommon. Perceptual disturbances causing discomfort are rarely reported after using psilocybin mushrooms, but they may be more likely if the drug is mixed with cannabis. There have been reports of such disturbances lasting months or years. Magic mushrooms have also been controversially associated with long term effects such as panic attacks, depression and paranoid delusions. On the other hand, magic mushrooms were rated as causing some of the least damage in the UK compared to other recreational drugs by experts in a study by the Independent Scientific Committee on Drugs. Other researchers have said that psilocybin is "remarkably non-toxic to the body's organ systems", explaining that the risks are indirect: higher dosages are more likely to cause fear and may result in dangerous behavior.
One study found that the most desirable results may come from starting with very low doses first, and trying slightly higher doses over months. The researchers explain that the peak experiences occur at quantities that are only slightly lower than a sort of anxiety threshold. Although risks of experiencing fear and anxiety increased somewhat consistently along with dosage and overall quality of experience, at dosages exceeding the individual's threshold, there was suddenly greater increases in anxiety than before. In other words, after finding the optimum dose, there are diminishing returns for using more (since risks of anxiety now increase at a greater rate).