Hallucinations versus delusions
A hallucination is a perception with no external stimulus, such as a voice when nobody is speaking; a delusion is a fixed belief that culture or religion does not explain.
Remember
A hallucination is what you perceive and a delusion is what you believe. Psychosis (experiences outside the normal experience of reality) is a collection of symptoms that includes both, and it is not a diagnosis in itself.
Memory aid
a hallucination is what you perceive, a delusion is what you believe
Ask whether the problem lies in perception or in belief to separate a hallucination from a delusion.
Psychosis is a collection of symptoms in which a person has experiences outside the normal experience of reality. It is not a diagnosis in itself. It includes hallucinations and delusions. A delusion is a problem of belief, while a hallucination is a problem of perception.
A hallucination is a sensory perception without an external stimulus. Hearing a voice when nobody is speaking is an example. Hallucinations can be in any sensory modality (in any sense). Hallucinations can also be normal: those that occur just before falling asleep (hypnagogic hallucinations) are an example.
A delusion is a fixed, firmly held belief that is usually false. It lies outside the person's cultural norms, meaning their culture or religion does not explain it, and it is unshakable: reasoning and evidence do not move it. A belief held within the person's own religious or cultural group is normally not treated as a delusion. A delusion of persecution is the belief that others are plotting against the person.
An illusion is a different thing again: it is a misinterpretation of a real external stimulus, such as seeing a coat as a person.
Insight is the degree to which a person is aware of their condition and its relation to their symptoms. It is often poor in psychosis, and denying being ill shows poor insight.
Key facts
- Hallucination
- a sensory perception without an external stimulus, in any sense.
- Delusion
- a fixed, firmly held belief outside the person's cultural norms that cannot be reasoned away.
- Cultural test
- a belief within the person's own religious or cultural group is normally not treated as delusional.
- Illusion
- a misinterpretation of a real external stimulus.
- Psychosis
- a collection of symptoms that includes hallucinations and delusions, and not a diagnosis in itself.
- Insight
- the degree to which a person is aware of their condition, often poor in psychosis.
Exam traps
- A sensory perception without an external stimulus defines a hallucination and not a delusion, because a delusion is a belief and not a perception.
- A belief that follows a hallucination is one possible route to a delusion and not the definition of delusions in general, because many delusions arise without a preceding hallucination.
- A misperception of a real stimulus is an illusion and not a delusion, because an illusion is a misinterpretation of a real external stimulus, while a delusion is a belief and not a perception.
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