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Clinical Review

ABC of mental health: Schizophrenia

BMJ 1997; 315 doi: (Published 12 July 1997) Cite this as: BMJ 1997;315:108
  1. Trevor Turner


    Schizophrenia is a relatively common form of psychotic disorder (severe mental illness). Its lifetime prevalence is nearly 1%, its annual incidence is about 10-15 per 100 000, and the average general practitioner cares for 10-20 schizophrenic patients depending on the location and social surroundings of the practice. It is a syndrome with various presentations and a variable, often relapsing, long term course.

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    Although schizophrenia is publicly misconceived as “split personality,” the diagnosis has good reliability, even across ages and cultures, though there is no biochemical marker. Onset before the age of 30 is the norm, with men tending to present some four years younger than women. Clues as to aetiology are tantalising, and management remains endearingly clinical.


    Evidence for a genetic cause grows stronger: up to 50% of identical (monozygotic) twins will share a diagnosis, compared with about 15% of non-identical (dizygotic) twins. The strength of genetic factors varies across families, but some 10% of a patient's first degree relatives (parents, siblings, and children) will also be schizophrenic, as will 50% of the children of two schizophrenic parents.

    Premorbid abnormalities of speech and behaviour may be present during childhood. The role of obstetric complications and viral infection in utero remains unproved. Enlarged ventricles and abnormalities of the temporal lobes are not uncommon findings from computed tomography of the brain. Thus, a picture is emerging of a genetic brain disorder, enhanced or brought out by subtle forms of environmental damage.

    Clinical features

    Symptoms are characterised most usefully as positive or negative, although the traditional diagnostic subcategories (hebephrenic, paranoid, catatonic, and simple) have mixtures of both

    Positive symptoms and signs

    Clinical features suggesting diagnosis of schizophrenia

    • Third person auditory hallucinations

    Running commentary on person's actions

    Two or more voices discussing the person

    Voices speaking the person's thoughts

    • Alien thoughts being inserted into or withdrawn from person's mind

    • Person's thoughts being broadcast or read by …

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