Is there a continuum of psychotic experiences in the general population?

AIMS: Schizophrenia is a severe mental illness that affects 1% of the population. The diagnosis is made according to current diagnostic systems of DSM-IV (American Psychiatric Association, 1994) and ICD-10 (World Health Organisation, 1992), on the basis of characteristic 'positive' and 'negative' symptoms. The traditional model assumes a categorical view of the schizophrenia syndrome and its core symptoms, in which differences between psychotic symptoms and their normal counterparts are considered to be qualitative. An alternative, dimensional approach assumes that schizophrenia is not a discrete illness entity, but that psychotic symptoms differ in quantitative ways from normal experiences and behaviours. This paper reviews evidence for the continuity of psychotic symptoms with normal experiences, focusing on the symptoms of hallucinations and delusions.
METHODS: A qualitative review of the relevant literature.
RESULTS: The literature suggests that although current epidemiological approaches yield substantial evidence for a continuum view, it is rarely interpreted as such.
CONCLUSIONS: The traditional concept of schizophrenia as a homogeneous disease entity has become outdated and is in dire need of a more valid and clinically useful successor.