background
Psilocybin mushrooms are better known as psychedelic mushrooms or "shrooms". They are mushrooms with the chemicals psilocybin and psilocin. They are ingested. Sometimes poisonous mushrooms can be mistaken for psychedelic mushrooms and will be eaten thus causing the consumer to die. Extreme caution is recommended when picking these mushrooms. They are illegal in the US but in some countries they are legal. (wikipedia.org)
severity
The effects of psychedelic mushrooms are not very severe however in very rare cases there have been symptoms of hallucinogen persisting perception disorder. Psychedelic mushrooms are considered one of the least damage causing drugs in existence. They also have no apparent toxic damage on the body's organs. (wikipedia.org)
Longer lasting effects
There are no long lasting effects of psychedelic mushrooms other than the rare case of hallucinogen persisting perception disorder.
*Images from Wikipedia