Psychiatric disorder before and after exposure to violent injury: A nationwide Norwegian register-based cohort study

Interpersonal violent injury is associated with increased risk of subsequent psychological problems, but pre-existing psychopathology may complicate this association in ways that are poorly understood. Using nationwide longitudinal registry data from Norway, we tested how psychiatric history modified the association between violent injury exposure and subsequent psychiatric disorder, and examined disorder continuity before vs. after violent injury. We identified all individuals presenting to emergency services in 2010-2018 with a violent injury, along with sex- and age-matched comparison individuals from the general population. The primary outcome was subsequent psychiatric disorder, observed through December 31, 2018, with secondary analyses examining psychiatric diagnoses pre- vs. post-injury. Of the 28,276 violence-injured patients, 20% had a history of psychiatric disorder, vs. 6% of the 282,760 comparison individuals. In Cox regression models, violence-injured patients had substantially higher rates of any subsequent psychiatric disorder when compared to matched peers (HR_adj: 2.36; 95% CI: 2.29, 2.42), but this association was confounded and modified by psychiatric history. Continuity of psychiatric diagnosis before and after injury was high among violence-injured patients, but they were also more likely than the comparison group to receive a new diagnosis, potentially indicating incident onset of new psychiatric disorder associated with violence exposure. Violence-injured patients face substantial burden of psychiatric disorder, especially for substance use and mood/anxiety disorders; clinical and public health strategies are needed to address this burden, which precedes violent injury in some cases but is likely provoked by it in others.