Delusion

A delusion is a fixed belief that a person holds with such conviction that it does not change even when confronted with clear and reasonable evidence contradicting it. This distinguishes a delusion from an ordinary false belief, a confabulated memory, a dogma one has simply been taught, or a perceptual mistake such as an illusion or hallucination, all of which a person can typically revise once shown convincing evidence. Psychiatrists and psychologists note that telling a genuine delusion apart from a strongly and stubbornly held personal conviction is not always straightforward, and the distinction depends partly on the degree to which the person clings to the belief in the face of contrary evidence. Delusions are one of the defining features of several serious psychotic conditions, appearing in schizophrenia, paraphrenia, the manic phase of bipolar disorder, and psychotic depression. Because a delusion can take almost any subject as its content, from persecution to grandiosity to jealousy, recognizing and assessing delusional belief is a central part of psychiatric evaluation across this whole range of conditions.