Hallucinogens are drugs which affect the central nervous system, producing hallucinations which may be visual, sensory, auditory, olfactory, or tactile. While many drugs can cause hallucinogenic effects, many people use the term specifically to refer to drugs which are taken deliberately with the intent of experiencing hallucinations. Therefore, a drug like LSD is a hallucinogen, whereas an antipsychotic drug like Trifluoperazine which can produce hallucinations is not known as a hallucinogen.
These psychoactive drugs work by disrupting the neurotransmitters in the brain, sending misfired and mixed messages. Depending on the drug and the dosage, someone can experience a variety of hallucinations as his or her brain attempts to cope with the drug, which is often a toxin. In some cases, hallucinogens can actually damage the brain, with repeat use of drugs like LSD being linked with long-term effects like random distortions of the visual field.
Researchers tend to break hallucinogens into three basic categories. Deliriants are drugs which induce a state of delirium, characterized by confusion, blurred vision, stupor, compulsive motion, and a dreamlike state. Dissociative drugs interrupt communication between various parts of the brain, causing people to feel disconnected from themselves and the world around them. Psychedelics fundamentally alter perception, distorting the visual field and causing manifestations of things which are not really there. Some cultures believe that psychedelics reveal the hidden nature of the mind.
Some examples of psychedelics include: ayahuasca, psilocybin, peyote, mescaline, bufotenine, and LSD. Salvia divinorum, fly agaric, and iboga are some instances of well-known dissociatives, while nightshade, henbane, and mandrake can all induce a state of delerium.
Many natural hallucinogens have a very long history in cultures all of the world. Historically, some shamans and other religious officiants consumed hallucinogens in an attempt to communicate with a higher power, or to explore their own minds. The use of such drugs was often tightly controlled, with a religious rather than recreational nature. Today, hallucinogens are most commonly used for recreational purposes, although the religious use of certain hallucinogens such as peyote is protected by law.
In many countries, access to hallucinogens is extremely limited by law. Because these drugs are not efficacious in the treatment of medical conditions, and they can be potentially dangerous, some governments have outlawed their production, sale, and possession. People who violate drug laws may find themselves subject to severe punishments. Because some cultures do have a history of using psychoactive drugs in religious practice, special exceptions may be granted to people in certain religions and ethnic groups.