Hallucinogen Use Disorder is an addiction to hallucinogens, including ketamine (special K), phencyclidine (PCP), LSD (acid), MDMA (ecstasy), mescaline, psilocybin (magic mushrooms), salvia, and many other psychedelic drugs. Hallucinogens cause psychoactive, mind-altering effects such as seeing, hearing, or feeling things that aren’t really there. Taking hallucinogens can cause frightening hallucinations, disorientation, poor judgment, and dangerous risk-taking behavior. Physiological effects include elevated heart rate, increased blood pressure, dilated pupils, and often can induce nausea and vomiting. Repeated use of hallucinogens such as LSD or ecstasy leads to tolerance and can result in psychological dependence.