Background. Head injury has been reported to increase the likelihood of the development of schizophrenia-like psychosis (SLP), but its features and risk factors have been insufficiently investigated.

Method. Between 1987 and 1997, we examined 45 referred patients with SLP following brain trauma. These subjects were matched with 45 head-injured subjects without SLP on age (current and at injury) and gender, and their case records reviewed systematically. The groups were compared and logistic regression analyses performed.

Results.The psychoses had a mean age of onset of 26·3 years, a mean latency of 54·7 months after head injury, usually a gradual onset and a subacute or chronic course. Prodromal symptoms were common and depression often present at onset. Paranoid delusions and auditory hallucinations were the predominant features, with formal thought disorder, catatonic features and negative symptoms being uncommon. The SLP group had more widespread brain damage on neuroimaging, especially in the left temporal and right parietal regions, and were more impaired cognitively. Fewer (non-significantly) SLP subjects had epilepsy which was more likely to be well-controlled in this group. On regression analysis, a positive family history of psychosis and duration of loss of consciousness were the best predictors of SLP.

Conclusions. Head injury-related psychosis is usually paranoid-hallucinatory and subacute or chronic in its presentation. A genetic predisposition to schizophrenia and severity of injury with significant brain damage and cognitive impairment may be vulnerability factors.