Researchers affiliated with University of Oxford, Karolinska Institute, and Örebro University, Sweden, conducted a nationwide within-individual study of all persons born in Sweden between 1958 and 1988 in order to assess the risk of the individual engaging in violent criminal behavior within 7 days of exposure to a trigger such as stressful life event, injury, or substance intoxication.

The goal was to identify putative risk factors and triggers for subsequent violent criminality in more than 34 000 and 29 000 individuals diagnosed with either schizophrenia spectrum disorders or bipolar disorder, respectively, as well as in more than 2.5 million unaffected control participants. The outcome variable was conviction for violent crime.

The findings, published in JAMA Psychiatry, indicate that stressful life events (ie, prior exposure to violence and parental bereavement), injury-related triggers [ie, traumatic brain injury (TBI), self harm, and unintentional injuries], and substance intoxication significantly contribute to elevated, short-term risk of violent offending in the week following exposure to one of these triggers, compared with the rate of violent crimes in earlier control periods within the same population.

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In the conditional logistic regression models, the researchers controlled for individual factors including sex and race/ethnicity, since the comparisons of the risk of violence were made within each study participant, as opposed to between participants. When compared with controls, all indicators of poor psychosocial functioning (ie, low family income, low educational attainment, residence in deprived neighborhood, high unemployment, social assistance, and disability pension) were more commonly observed in patients diagnosed with psychotic disorders, especially schizophrenia.

“Absolute risks [the incidence in a population] for violent crime were typically highest among individuals diagnosed with schizophrenia, followed by those with bipolar disorder and, last, the unaffected controls,” and, “the rates of a violent crime occurring in the week following exposure to a trigger [ie, stressful life events, injury, substance intoxication] were considerably elevated when compared with their respective control periods,” the authors noted.

The largest 7-day absolute risk of criminal, violent behavior was observed after exposure to violence (70-177 violent crimes per 10 000 individuals). More specifically, rates of violent crime in the week following exposure to violence, per 10 000 individuals, were as follows: schizophrenia spectrum disorders (177; 95% CI, 133-230); bipolar disorder (83; 95% CI, 52-127); and, unaffected controls (70; 95% CI, 64-77).

The next largest 1-week absolute risk of violent crime in patients with schizophrenia was observed after TBI. More specifically, rates of violent behavior in the 7 days following TBI, per 10 000 individuals, were as follows: schizophrenia spectrum disorders (93; 95% CI, 68-123); bipolar disorder (32; 95% CI, 17-54); and, unaffected controls (24; 95% CI, 22-26).

The third largest 7-day absolute risk of violent criminality in individuals with schizophrenia was observed following substance intoxication. More specifically, rates of violent behavior within 1 week, per 10 000 individuals, were as follows: schizophrenia spectrum disorders (65; 95% CI, 46-88); bipolar disorder (34; 95% CI, 19-55); and, unaffected controls (33; 95% CI, 29-38).

It is important to note that the observed effects of triggers that were included in the analysis weakened over time. For example, the relative risk [a ratio of the risk of individuals exposed to a trigger to the risk of individuals not exposed to a trigger] of criminally violent offending in patients with schizophrenia within a week of exposure to violence was increased almost 13-fold [adjusted odds ratios (aOR, 12.7; 95% CI, 8.2-19.6)]. In the second (aOR, 0.8; 95% CI, 0.4-2.0) and third (aOR, 1.1; 95% CI, 0.5-2.3) week following exposure to violence, however, the relative risk of violent crime in those same individuals dropped significantly. The reported data indicate that similar relationship also exists in patients with bipolar disorder and in unaffected controls.

Taken together, although other factors may play a role, stressful events, injuries, and substance intoxication are all significantly associated with subsequent rate of violent criminality within 7 days of trigger exposure in patients with psychotic disorder and in unaffected individuals, compared with the rate in earlier control periods.

In the accompanying editorial, Dr Volavka wrote, that the findings “suggest that the association between the trigger and subsequent violence is robust and causal,” and that “it is possible that we are seeing a universal phenomenon, encompassing many triggers, populations, and species.”

According to the authors, “identifying triggers for violence has not been incorporated into many risk assessment approaches.” And, based on the findings, “… opportunities [exist] to improve the monitoring and management of violence risk.”

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Sariaslan A, Lichtenstein P, Larsson H, Fazel S. Triggers for violent criminality in patients with psychotic disorders. JAMA Psychiatry. 2016. doi: 10.1001/jamapsychiatry.2016.1349.


Volavka J. Triggering violence in psychosis. JAMA Psychiatry. 2016. doi: 10.1001/jamapsychiatry.2016.1348.