Hallucinogens cause people to experience—you guessed it—hallucinations, imagined experiences that seem real. PDF for Mind Over Matter - Hallucinogens [PDF - 647 KB] The Brain's Response to Hallucinogens Where Do Hallucinogens Come From? How Hallucinogens Affect Your Senses How MDMA and MDA Affect Your Brain Actions of PCP in the Brain LSD: The Most Commonly Used Hallucinogen The Search Continues The Brain's Response to Hallucinogens › Español