A small group of individuals with mental illness is repeatedly involved in violence. Little is known about how often and how consistently these high-risk individuals experience delusions or hallucinations just before a violent incident. To address these questions, data from the MacArthur Violence Risk Assessment Study was used to identify 305 violent incidents associated with 100 former inpatients with repeated violence (representing 50% of incidents and 9% of participants), and test whether psychosis-preceded incidents cluster within individuals. Results indicated that (a) psychosis immediately preceded 12% of incidents, (b) individuals were “fairly” consistent in their violence type (ICC = .42), and (c) those with exclusively “non-psychosis-preceded” violence (80%) could be distinguished from a small group who also had some psychosis-preceded violence (20%). These findings suggest that psychosis sometimes foreshadows violence for a fraction of high-risk individuals, but violence prevention efforts should also target factors like anger control and social deviance.

Paul S. Appelbaum et al., Psychosis Uncommonly and Inconsistently Precedes Violence Among High Risk Individuals, 4 Clinical Psychological Science 40–49 (2016).