Psychosis following head injury: A critical review

Schizophrenia is the most common form of psychotic mental disorder, with a point prevalence generally estimated to lie between 0.6-1.0%. Genetically informative studies have indicated a multifactorial aetiology, with an important heritable (genetic) component, but with environmental exposures also undoubtedly relevant. The "neurodevelopmental hypothesis" has informed a body of research that fairly consistently identifies birth complications as a risk factor for the later onset of schizophrenia.(1 2) Injury to the head or brain after birth and beyond has been posited as a risk factor for psychosis for many decades but has enjoyed little systematic research (see Lishman,(3) van Reckurn et al,(4) and Fujii and Ahmed(5) for reviews). The purpose of this article is to review this information systematically. Computerised databases including Medline and Psychinfo were searched using head/brain injury and psychosis or schizophrenia as search terms, covering the period from 1966 to end 2003. Citations from published reviews were also retrieved and yielded important articles and monographs, sonic published more than two decades ago, not included in these databases. Four types of study design have been used to assess the relation between head injury and schizophrenia: the case report; the long term follow up of series of head injured persons; the cross sectional survey; and the case-control study.