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PsychosisTraumatic Brain Injury
SIR: Fujii and Ahmed1 have reported an interesting study of the risk factors for the development of schizophrenia-like psychosis (SLP) following head injury. The clinical importance of this association is best appreciated by psychiatrists involved in medicolegal work who are called upon by courts to speculate on the role played by head injury in the causation of psychosis. We recently published a similar study2 and wish to highlight some of the salient similarities and differences in the findings. Our sample was somewhat larger (N=45), we matched nonpsychiatric head-injured comparison subjects on age (current and at injury) and gender, and both groups were drawn from the same sources.
Like Fujii and Ahmed, we found a predominance of men in the sample, but that was the case in the head injury group as a whole. Male preponderance has been reported in secondary schizophrenias in general.3 More striking was the similarity of age at the time of brain injury in our SLP group (mean 21.6 years, range 2—49) and that of the Fujii and Ahmed study (mean 21.4 years, range 3—48). The mean latency period for the development of psychosis after head injury was 54.7 months in our study compared with 52 months in theirs. Unlike Fujii and Ahmed, we did not have systematic data about past head injuries except that our subjects commonly reported previous mild injuries. These authors emphasize the importance of past injuries, whereas the similarities in the ages and latency periods in the two studies suggest to us that the index injury is likely to be the more salient one.
Notable difference between the findings of the two studies is that our SLP subjects had more severe brain injury as measured by the duration of loss of consciousness, as has been previously reported,4,5 whereas the Fujii and Ahmed subjects with psychosis were more likely to have had a mild injury. Fujii and Ahmed explain their finding in terms of a possible sampling bias. Another major difference between the two studies, however, was the exclusion of subjects with a family history of schizophrenia by Fujii and Ahmed. In fact, a genetic predisposition to schizophrenia emerged as a significant risk factor for psychosis in our study, with the brain injury presumably bringing out a vulnerability.
Fujii and Ahmed do not state how many subjects were excluded on the basis of a positive family history. In trying to bring the two studies together, it could be argued that the brain injury is acting on a brain that was already vulnerable—owing to a genetic predisposition, as suggested by our study, or a prior neurological disease, according to Fujii and Ahmed. The different findings are possibly a consequence of different populations being examined. The similarities highlighted above are noteworthy and argue that traumatic brain injury is a serious risk factor for psychosis that deserves further study.
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