In Reply
We would like to thank Dr. Sachdev for his interest in our study. We concur with his argument that traumatic brain injury (TBI) is a significant risk factor for psychosis that deserves further study. Studies of monozygotic twins report that the concordance rate for schizophrenia is roughly 50%.1 This would suggest that environmental factors are also important. Thus far much of the attention in environmental factors has focused on birth complications and illness or maternal stressors during gestation.1 The size effects for these factors, however, are relatively small (between 2 and 3).1 Results from Dr. Sachdev's study as well as ours would suggest that TBI may be another significant risk factor for persons with and without a genetic predisposition for schizophrenia.2,3 Indeed there is evidence that many psychiatric patients have sustained TBI within one year prior to hospitalization.4 Moreover, in many other cases a prior TBI is undocumented in the medical chart.4 We hope that both studies will motivate further investigations into the relationship between traumatic brain injury and psychosis.
1 Jones P, Cannon M: The new epidemiology of schizophrenia. Psychiatr Clin N Am 1998; 21:1-25Crossref, Medline, Google Scholar
2 Fujii DE, Ahmed I: Risk factors in psychosis secondary to brain injury. J Neuropsychiatry Clin Neurosci 2001; 13:61-69Link, Google Scholar
3 Sachdev P, Smith JS, Cathcart S: Schizophrenia-like psychosis following traumatic brain injury: a chart-based descriptive and case-control study. Psychol Med 2001; 31:231-239Crossref, Medline, Google Scholar
4 Burg JS, McGuire LM, Burright RG, et al: Prevalence of traumatic brain injury in an inpatient psychiatric population. J Clin Psychol Med Set 1996; 3:243-251Crossref, Medline, Google Scholar