Handgun Ownership and Suicide in California.

BACKGROUND: Research has consistently identified firearm availability as a risk factor for suicide. However, existing studies are relatively small in scale, estimates vary widely, and no study appears to have tracked risks from commencement of firearm ownership. METHODS: We identified handgun acquisitions and deaths in a cohort of 26.3 million male and female residents of California, 21 years old or older, who had not previously acquired handguns. Cohort members were followed for up to 12 years 2 months (from October 18, 2004, to December 31, 2016). We used survival analysis to estimate the relationship between handgun ownership and both all-cause mortality and suicide (by firearm and by other methods) among men and women. The analysis allowed the baseline hazard to vary according to neighborhood and was adjusted for age, race and ethnic group, and ownership of long guns (i.e., rifles or shotguns). RESULTS: A total of 676,425 cohort members acquired one or more handguns, and 1,457,981 died; 17,894 died by suicide, of which 6691 were suicides by firearm. Rates of suicide by any method were higher among handgun owners, with an adjusted hazard ratio of 3.34 for all male owners as compared with male nonowners (95% confidence interval [CI], 3.13 to 3.56) and 7.16 for female owners as compared with female nonowners (95% CI, 6.22 to 8.24). These rates were driven by much higher rates of suicide by firearm among both male and female handgun owners, with a hazard ratio of 7.82 for men (95% CI, 7.26 to 8.43) and 35.15 for women (95% CI, 29.56 to 41.79). Handgun owners did not have higher rates of suicide by other methods or higher all-cause mortality. The risk of suicide by firearm among handgun owners peaked immediately after the first acquisition, but 52% of all suicides by firearm among handgun owners occurred more than 1 year after acquisition. CONCLUSIONS: Handgun ownership is associated with a greatly elevated and enduring risk of suicide by firearm. (Funded by the Fund for a Safer Future and others.).

Homicide Deaths Among Adult Cohabitants of Handgun Owners in California, 2004 to 2016 : A Cohort Study.

BACKGROUND: Although personal protection is a major motivation for purchasing firearms, existing studies suggest that people living in homes with firearms have higher risks for dying by homicide. Distribution of those risks among household members is poorly understood. OBJECTIVE: To estimate the association between living with a lawful handgun owner and risk for homicide victimization. DESIGN: This retrospective cohort study followed 17.6 million adult residents of California for up to 12 years 2 months (18 October 2004 through 31 December 2016). Cohort members did not own handguns, but some started residing with lawful handgun owners during follow-up. SETTING: California. PARTICIPANTS: 17 569 096 voter registrants aged 21 years or older. MEASUREMENTS: Homicide (overall, by firearm, and by other methods) and homicide occurring in the victim's home. RESULTS: Of 595 448 cohort members who commenced residing with handgun owners, two thirds were women. A total of 737 012 cohort members died; 2293 died by homicide. Overall rates of homicide were more than twice as high among cohabitants of handgun owners than among cohabitants of nonowners (adjusted hazard ratio, 2.33 [95% CI, 1.78 to 3.05]). These elevated rates were driven largely by higher rates of homicide by firearm (adjusted hazard ratio, 2.83 [CI, 2.05 to 3.91]). Among homicides occurring at home, cohabitants of owners had sevenfold higher rates of being fatally shot by a spouse or intimate partner (adjusted hazard ratio, 7.16 [CI, 4.04 to 12.69]); 84% of these victims were female. LIMITATIONS: Some cohort members classified as unexposed may have lived in homes with handguns. Residents of homes with and without handguns may have differed on unobserved traits associated with homicide risk. CONCLUSION: Living with a handgun owner is associated with substantially elevated risk for dying by homicide. Women are disproportionately affected. PRIMARY FUNDING SOURCE: The National Collaborative on Gun Violence Research, the Fund for a Safer Future, the Joyce Foundation, Stanford Law School, and the Stanford University School of Medicine.

Assembly of the LongSHOT cohort: public record linkage on a grand scale.

BACKGROUND: Virtually all existing evidence linking access to firearms to elevated risks of mortality and morbidity comes from ecological and case-control studies. To improve understanding of the health risks and benefits of firearm ownership, we launched a cohort study: the Longitudinal Study of Handgun Ownership and Transfer (LongSHOT). METHODS: Using probabilistic matching techniques we linked three sources of individual-level, state-wide data in California: official voter registration records, an archive of lawful handgun transactions and all-cause mortality data. There were nearly 28.8 million unique voter registrants, 5.5 million handgun transfers and 3.1 million deaths during the study period (18 October 2004 to 31 December 2016). The linkage relied on several identifying variables (first, middle and last names; date of birth; sex; residential address) that were available in all three data sets, deploying them in a series of bespoke algorithms. RESULTS: Assembly of the LongSHOT cohort commenced in January 2016 and was completed in March 2019. Approximately three-quarters of matches identified were exact matches on all link variables. The cohort consists of 28.8 million adult residents of California followed for up to 12.2 years. A total of 1.2 million cohort members purchased at least one handgun during the study period, and 1.6 million died. CONCLUSIONS: Three steps taken early may be particularly useful in enhancing the efficiency of large-scale data linkage: thorough data cleaning; assessment of the suitability of off-the-shelf data linkage packages relative to bespoke coding; and careful consideration of the minimum sample size and matching precision needed to support rigorous investigation of the study questions.

Patterns of handgun divestment among handgun owners in California.

BACKGROUND: Little is known about voluntary divestment of firearms among US firearm owners. Here, we aim to estimate the proportion of handgun owners who divest their handguns in the years following their initial acquisition; examine the timing, duration, and dynamics of those divestments; and describe characteristics of those who divest. METHODS: We use data from the Longitudinal Study of Handgun Ownership and Transfer, a cohort of registered voters in California with detailed information on 626,756 adults who became handgun owners during the 12-year study period, 2004-2016. For the current study, persons were followed from the time of their initial handgun acquisition until divestment, loss to follow-up, death, or the end of the study period. We describe the cumulative proportion who divest overall and by personal and area-level characteristics. We also estimate the proportion who reacquired handguns among persons who divested. RESULTS: Overall, 4.5% (95% CI 4.5-4.6) of handgun owners divested within 5 years of their first acquisition, with divestment relatively more common among women and among younger adults. Among those who divested, 36.6% (95% CI 35.8-37.5) reacquired a handgun within 5 years. CONCLUSIONS: Handgun divestment is rare, with the vast majority of new handgun owners retaining them for years.

Suicide Deaths Among Women in California Living With Handgun Owners vs Those Living With Other Adults in Handgun-Free Homes, 2004-2016.

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.