• Incidence: 16.00 cases per 100,000 person-years
  • Peak incidence: 30-40 years
  • Sex ratio: more common in males 1.4:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


The strongest risk factor for developing a psychotic disorder (including schizophrenia) is family history. Having a parent with schizophrenia leads to a relative risk (RR) of 7.5.

Risk of developing schizophrenia
  • monozygotic twin has schizophrenia = 50%
  • parent has schizophrenia = 10-15%
  • sibling has schizophrenia = 10%
  • no relatives with schizophrenia = 1%

Other selected risk factors for psychotic disorders include:
  • Black Caribbean ethnicity - RR 5.4
  • Migration - RR 2.9
  • Urban environment- RR 2.4
  • Cannabis use - RR 1.4

Clinical features

Schneider's first rank symptoms may be divided into auditory hallucinations, thought disorders, passivity phenomena and delusional perceptions:

Auditory hallucinations of a specific type:
  • two or more voices discussing the patient in the third person
  • thought echo
  • voices commenting on the patient's behaviour

Thought disorder*:
  • thought insertion
  • thought withdrawal
  • thought broadcasting

Passivity phenomena:
  • bodily sensations being controlled by external influence
  • actions/impulses/feelings - experiences which are imposed on the individual or influenced by others

Delusional perceptions
  • a two stage process) where first a normal object is perceived then secondly there is a sudden intense delusional insight into the objects meaning for the patient e.g. 'The traffic light is green therefore I am the King'.

Other features of schizophrenia include
  • impaired insight
  • incongruity/blunting of affect (inappropriate emotion for circumstances)
  • decreased speech
  • neologisms: made-up words
  • catatonia
  • negative symptoms: incongruity/blunting of affect, anhedonia (inability to derive pleasure), alogia (poverty of speech), avolition (poor motivation)

*occasionally referred to as thought alienation


NICE published guidelines on the management of schizophrenia in 2009.

Key points:
  • oral atypical antipsychotics are first-line
  • cognitive behavioural therapy should be offered to all patients
  • close attention should be paid to cardiovascular risk-factor modification due to the high rates of cardiovascular disease in schizophrenic patients (linked to antipsychotic medication and high smoking rates)


Factors associated with poor prognosis
  • strong family history
  • gradual onset
  • low IQ
  • premorbid history of social withdrawal
  • lack of obvious precipitant