Hallucinations Hallucinations are defined as the perception of an external object when no object is actually present. There are many reasons why people hallucinate. Some reasons for hallucinations are prescription medications (SSRIs), illegal drugs (LSD), and sleep disorders (narcolepsy). Some causes of hallucinations stem from taking medications, both prescribed and illegal. Both produce the same effect. Hallucinations resulting from these have been described as déjà vu, or hearing or seeing things that aren't really there. Prescription medications such as SSRI, used for ulcers, have been reported to have hallucinations as a side effect. Dronabinol, used to treat nausea in chemotherapy, has had the same reports. People with Parkinson's disease have complained of hallucinations while taking an antibiotic called selegiline. Even illegal drugs have been reported to produce hallucinations. These drugs are called hallucinogens. Lysergic acid diethylamide (LSD) is a commonly used hallucinogen in the underground drug world. The hallucinations resulting from this are very unrealistic. Users claim to see very vivid colors and geometric shapes during a "journey". They tend to hear and see things that aren't there. For example, they will hear someone call their name or see something absurd like a purple elephant. Peyote is another illegal drug that creates hallucinations in those who use it. It is very similar to LSD in that it has the same hallucinations. It is derived from a small cactus in the southwestern region of the United States and in some parts of Mexico. Several studies have been conducted on hallucinations and the effects of drugs in relation to hallucinations. Ronald Seigle conducted a study on the effects of peyote on the Huichol Indians. He concluded that the Indians' hallucinations were remarkably similar to those of college kids taking similar drugs. He believed that the parts of the brain that respond to incoming stimuli became disorganized while the entire central nervous system became excited. There are no long-term effects of having hallucinations unless they occur through medications, in which case the medication will confuse the user. in the future.