Magic mushrooms contain psilocybin, a natural psychedelic alkaloid. When ingested, the body breaks down psilocybin into psilocin, which affects the serotonin signaling system in two main ways: by stopping the reuptake of serotonin (which leads to higher levels of serotonin in the brain) and by directly binding to specific serotonin receptors. This increase in serotonin and serotonin signals is what causes hallucinations also known as a “trip”.