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Mild Brain Injury Increases Risks for All Psychiatric Outcomes

A new study published in the American Journal of Psychiatry out of Denmark found an increase in risk for all psychiatric outcomes after brain injury.  The Danish researchers investigated the relationship between head injury and subsequent psychiatric disorders.  According to the abstract, the authors used linkable Danish nationwide population-based registers to investigate the incidents of schizophrenia spectrum disorders, unipolar  depression, bipolar disorder, and organic mental disorders in 113,906 not six individuals born between 1977-2000 who received in inpatient or emergency department diagnosis of head injury .  Data were analyzed by survival analysis and adjusted for gender, age, calendar year, presence of psychiatric family history, epilepsy, infections, auto immune diseases, and fractures not involving the skull or spine. 

The results and conclusions were:

Results  Head injury was associated with a higher risk of schizophrenia (incidence rate ratio [IRR]=1.65, 95% CI=1.55–1.75), depression (IRR=1.59 95% CI=1.53–1.65), bipolar disorder (IRR=1.28, 95% CI=1.10–1.48), and organic mental disorders (IRR=4.39, 95% CI=3.86–4.99). This effect was larger than that of fractures not involving the skull or spine for schizophrenia, depression, and organic mental disorders, which suggests that the results were not merely due to accident proneness. Head injury between ages 11 and 15 years was the strongest predictor for subsequent development of schizophrenia, depression, and bipolar disorder. The added risk of mental illness following head injury did not differ between individuals with and without a psychiatric family history.

Conclusions  This is the largest study to date investigating head injury and subsequent mental illness. The authors demonstrated an increase in risk for all psychiatric outcomes after head injury. The effect did not seem to be solely due to accident proneness, and the added risk was not more pronounced in persons with a psychiatric family history.

Orlovska S et al. Head injury as risk factor for psychiatric disorders: A nationwide register-based follow-up study of 113,906 persons with head injury. Am J Psychiatry 2013 Dec 10; [e-pub ahead of print]. (

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