Hallucinogens and dissociative drugs are both categories of drugs that alter a persons’ state of mind and mood. Hallucinogens can cause a person to hallucinate — that is to see, hear, or feel things that aren’t actually real. Hallucinogens include LSD, Mescaline (Peyote), Psilocybin, and Psilocyn (Mushrooms). Dissociative drugs, such as Ketamine or PCP, alter a persons state of mind and mood but do not cause a person to hallucinate. Dissociative drugs cause a person to detach, or dissociate, from his or her surroundings.

First synthesised from morphine in 1874, heroin was not extensively used in medicine until the beginning of this century. Commercial production of the new pain remedy was first started in 1898. While it received widespread acceptance from the medical profession, physicians remained unaware of its potential for addiction for years. The first comprehensive control of heroin in the United States was established with the Harrison Narcotic Act of 1914.