hallucination
Meaning of hallucination: Which sense is involved narrows the cause sharply, because heard voices and seen figures point in quite different clinical directions.
Definition of hallucination
A hallucination is a perception that occurs without any outside stimulus producing it, yet feels as real as an ordinary sensation. It can involve any sense: hearing voices, seeing figures or patterns, smelling something absent, tasting, or feeling movement on or under the skin. It differs from an illusion, which is a misreading of something genuinely present.
What does the sense involved suggest?
| Sense | Common associations |
|---|---|
| Hearing | Voices are most typical of primary psychiatric illness such as schizophrenia |
| Vision | More suggestive of a medical, neurological or drug cause; a core feature of dementia with Lewy bodies |
| Smell and taste | Brief unpleasant smells can precede a seizure arising in the temporal lobe |
| Touch | Sensations of insects on the skin are described in stimulant use and in alcohol withdrawal |
These are tendencies rather than rules, and any sense can be involved in almost any cause, but the pattern shapes where investigation starts.
Do healthy people have them?
Regularly. Hearing a name called or seeing a fleeting figure while falling asleep or waking is common and carries no significance; these are hypnagogic and hypnopompic experiences, tied to the boundary between waking and REM sleep. Briefly hearing or seeing a person who has died is frequently reported during bereavement. In Charles Bonnet syndrome, people losing their sight see detailed images, patterns or faces while knowing perfectly well the images are not real, and the cause is the loss of visual input rather than any mental illness. Severe sleep deprivation and extreme sensory monotony can also produce them in anyone.
What else brings them on?
Delirium from infection, organ failure, low oxygen or medication is among the most frequent causes in a hospital, and it fluctuates through the day in a way psychiatric illness usually does not. Withdrawal from alcohol or sedatives produces vivid visual and tactile experiences, and stimulants, hallucinogens and high doses of some prescribed drugs do the same. Fever in young children, migraine aura, epilepsy, Parkinson disease and its treatments all appear on the list. Because insight is often preserved outside psychiatric illness, someone may describe the experience clearly while knowing it is not real.
Used in a sentence
The patient reported auditory hallucinations that began several days before the emergency visit.
Good to know
A hallucination is distinguished from an illusion, which is a distorted perception of something that is actually present, since a hallucination has no external stimulus at all.
Word origin
Where “hallucination” comes from
From Latin hallucinari, meaning to wander in mind or dream, describing an experience disconnected from actual surroundings.