Background
In the United States (US), 61% of all suicide cases may involve firearms, and some evidence suggests that mental disorders may play a role in suicide by firearm. We performed the first systematic review and meta-analyses to investigate: (i) whether mental disorders are associated with suicide by firearm, and (ii) whether the risk of using a firearm compared with alternative means is associated with higher levels of suicide in individuals with a mental disorder
Methods and findings
We searched twelve databases from inception to the 24th of May 2020. We retrieved 22 observational studies conducted in the US. Random-effects meta-analyses showed individuals who had a diagnosis of a mental disorder had lower odds (odds ratios (OR)= 0.50, 95% CI: 0.36 to 0.69; I2=100 (95% CI: 87 to 100%), of dying by suicide with a firearm than those who did not have a diagnosis of a mental disorder. Secondary analysis showed that decedents who had a mental health diagnosis resulted in lower odds of dying by suicide by using firearms than using other means
Limitations
Risk of bias revealed a heterogeneous and poor definition of mental disorders as well as lack of control for potential demographic confounding factors. In the meta-analyses, studies were combined in the same analytic sample as 77% of these studies did not specify the type of mental disorder
Conclusion
While our results seem to suggest that having a mental disorder may not be consistently associated with the odds of dying by suicide using a firearm, the presence of substantial heterogeneity and high risk of bias precludes any firm conclusions.
