LAUSR

Importance Little is known about the extent to which secondhand exposure to household firearms is associated with risk of suicide in adults who do not own guns, most of whom are women. Objective To evaluate changes in risk of suicide among women living in gun-free households after one of their cohabitants became a handgun owner. Design, Setting, and Participants This cohort study observed participants for up to 12 years and 2 months from October 18, 2004, to December 31, 2016. Data were analyzed from April to November 2021. The study population included 9.5 million adult women in California who did not own guns and who entered the study while living with 1 or more adults in a handgun-free home. Exposures Secondhand exposure to household handguns. Main Outcomes and Measures Suicide, firearm suicide, nonfirearm suicide. Results Of 9.5 million women living in handgun-free homes, 331 968 women (3.5% of the study population; mean [SD] age, 41.6 [18.0] years) became exposed to household handguns during the study period. In the entire study population, 294 959 women died: 2197 (1%) of these were by suicide, 337 (15%) of which were suicides by firearm. Rates of suicide by any method during follow-up were higher among cohort members residing with handgun owners compared with those residing in handgun-free homes (hazard ratio, 1.43; 95% CI, 1.11-1.84). The excess suicide rate was accounted for by higher rates of suicide by firearm (hazard ratio, 4.32; 95% CI, 2.89-6.46). Women in households with and without handguns had similar rates of suicide by nonfirearm methods (hazard ratio, 0.90; 95% CI, 0.63-1.27). Conclusions and Relevance In this study, the rate of suicide among women was significantly higher after a cohabitant of theirs became a handgun owner compared with the rate observed while they lived in handgun-free homes.