• Robert J Snowden, Nicola S Gray, John Taylor, and Malcolm J MacCulloch.
• School of Psychology, Cardiff University, Cardiff, UK. snowden@cardiff.ac.uk
• Psychol Med. 2007 Nov 1;37(11):1539-49.

BackgroundActuarial instruments may be useful in predicting long-term violence in mentally disordered patients. We compared two instruments that differ in terms of what they are designed to predict (general versus violent recividism) and the inclusion of stable mental health variables.MethodA large sample of mentally disordered patients were scored on two risk assessment instruments, the Violence Risk Appraisal Guide (VRAG) and the Offender Group Reconviction Scale (OGRS), based on information at the point of discharge. Their criminal histories for at least 2 years following discharge were obtained from official records.ResultsBoth instruments were good predictors of both violent and general offending. Over shorter periods (0.85], which were significantly better than the OGRS. For longer follow-up periods the instruments had approximately equal prediction accuracy. However, both instruments predicted far more offences than were in fact recorded.ConclusionsThe VRAG is a very good predictor of future violence in the UK sample. The OGRS may also be of value as it can be completed quickly and without the need for mental health variables. Caution is needed, however, as both instruments appeared to over-predict the levels of reconvictions in this sample.

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