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Letters to the Editor
December 2010

Bipolar Disorder and Violent Crime: Time at Risk Reanalysis

Author Affiliations

Author Affiliations: Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford, England (Drs Fazel and Goodwin); and Center for Violence Prevention (Drs Fazel, Grann, and Långström) and Department of Medical Epidemiology and Biostatistics (Drs Lichtenstein and Långström and Mr Frisell), Karolinska Institutet, Stockholm, Sweden.

Arch Gen Psychiatry. 2010;67(12):1325-1326. doi:10.1001/archgenpsychiatry.2010.171

It has come to our attention that the design that we used in the 2 longitudinal studies on violent crime in bipolar disorder1 underestimated the relative risks of violent crime associated with patients with bipolar disorder, although the absolute risks of violent offending and substance abuse in bipolar disorder remain unchanged. Our design measured rates of violent crime in controls from age 15 years and in cases from after diagnosis. This meant that the time at risk was not similar between cases and controls. We discussed various other potential biases in our article, including the reliance on hospital data to ascertain the cases (which will likely overestimate relative risks) and conviction information to measure violence as an outcome (which will underestimate absolute risks), but would like to address this limitation in the present letter.

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