Objective To examine whether unintentionally injuring others is associated with subsequent mental illness, and whether mental illness is a risk factor for unintentionally injuring others.

Methods Onset of first psychiatric diagnoses was compared with onset of first unintentional injuring. Multivariate logistic regression estimated the association between unintentional injuring and lifetime prevalence of mental illness, specifically of Diagnostic and Statistical Manual of Mental Disorders IV disorders associated with trauma exposure among respondents of part II of the National Co-morbidity Survey Replication a household survey of 5692 US adults. Analyses controlled for age, sex, race and having been injured in a serious accident.

Results Of 5692 respondents, 110 reported unintentionally causing death or injury to another person. Unintentionally injuring others was a risk factor for subsequent mental health problems. Multivariate regression results showed an increased risk of subsequent depression (OR 3.1, CI 1.7 to 5.7), anxiety (OR 3.3, CI 1.6 to 6.6), posttraumatic stress disorder (PTSD) (OR 6.6, CI 3.1 to 14.0), alcohol use (OR 3.8, CI 1.9 to 7.3) and drug use (OR 8.0, CI 4.1 to 15.3). Conversely, mental health problems were a risk factor for unintentionally injuring another person. Multivariate regression results showed an increased risk of unintentional injuring among those with a prior diagnosis of depression, PTSD, alcohol use, and drug use.

Conclusions After injuring, unintentional injurers are likely to experience depression, anxiety, PTSD and drug or alcohol abuse/dependence compared with non-injurers. Those diagnosed with depression, anxiety, PTSD, alcohol or drug or alcohol abuse/dependence are more likely to cause serious injuries to others.