Hallucination facts

The Temptation of Saint Anthony (Grünewald) detail
The Temptation of Saint Anthony, Detail, Mathias Grünewald, 1515. This painting might have been influenced by the description of hallucinations.

A hallucination is seeing, hearing, tasting, smelling or feeling things that do not really exist. Usually people have to be awake and conscious to have hallucinations. That way, a person who sees or hears something that is not really there has a hallucination. Hallucinations are different from dreams. When people dream they are not awake. Hallucinations are also different from illusions. Illusions are based on real perceptions, which are distorted or interpreted in a wrong way.

Certain drugs can cause hallucinations.

People who have hallucinations are not necessarily ill, lack of sleep can also cause hallucinations. Hallucinations just before going to sleep or just after waking up are considered normal.

What are the different types of hallucinations?

Hallucinations can affect all of a person's senses. People with the mental illness of schizophrenia may hear sounds or voices that are not really there. People with certain mental illnesses may also have hallucinations in which they see a person or thing which is not really there. People are less likely to have hallucinations in which they smell or touch something that is not really there. Certain forms of epilepsy can cause hallucinations. Finally, hallucinations can be the result of certain substances taken or of certain physical constellations. Most of the time, these substances are taken to get the hallucinations. Sometimes, (severe) lack of sleep, or high fever can lead to hallucinations brought on by such viruses as the common cold.

How many people are affected by hallucinations?

Many studies have shown hallucinatory experiences take place across the world. Several studies, one of them done as early as 1894, have reported that approximately 10% of the population experience hallucinations. A recent survey of over 13,000 people reported a much higher figure. According to the study, almost 39% of the people reported hallucinatory experiences. 27% of the people reported daytime hallucinations, mostly outside the context of illness or drug use. From this survey, hallucinations affecting smell or taste seem the most common in the general population.


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