Psilocybin does not always cause active visual or auditory hallucinations. Instead, it distorts how some people that use the drug perceive objects and people already in their environment.The quantity of the drug a person consumes, their past experiences, and their expectations of how the experience will take shape can all impact the effects of psilocybin.This part of the brain affects mood, cognition, and perception. Hallucinogens also work in other regions of the brain that regulate arousal and panic responses.The hallucinogenic effects of psilocybin usually occur within 30 minutes after a person ingests it and last 4-6 hours. In some individuals, changes in sensory perception and thought patterns can last for several days.