Sexual Orientation and Exposure to Close Others' Self-Injurious Thoughts and Behaviors.

Importance: Sexual minority young adults experience disproportionately high rates of self-injurious thoughts and behaviors (SITB), including suicidal ideation, suicide attempts, and nonsuicidal self-injury (NSSI). While exposure to close others' SITB (eg, a friend or family member's suicide attempt) is a known risk factor for SITB, its role in sexual orientation disparities in SITB remains underexplored. Objective: To examine whether exposure to close others' SITB is associated with sexual orientation disparities in SITB. Design, Setting, and Participants: This cohort study assessed data from 2 nationally representative cohorts: the Swedish Pathways to Longitudinally Understanding Stress (PLUS) study (2023) and the Scottish Well-being Study ([SWS] conducted 2015-2018). The present study uses data only from the final wave of the PLUS study (2023) as this was the only wave that gathered information on exposure to close others' SITB (n = 1202). The present study also uses data from participants who completed the second through fourth follow-up waves of the SWS, as sexual orientation information was not collected at the first wave (n = 1828). Exposures: Sexual orientation (heterosexual vs sexual minority) was the primary exposure. Exposure to close others' SITB, assessed via validated measures, was the primary mediator. Main Outcomes and Measures: In both cohorts, primary outcomes assessed participants' own SITB. In the PLUS cohort, the primary outcome was suicidal ideation measured using the Suicidal Ideation Attributes Scale (scores range from 0 to 50, with higher scores indicating more severe suicidal ideation). In SWS, there were 5 primary outcomes assessing past-year presence of suicidal ideation, NSSI, NSSI ideation, and suicide attempt as well as a composite indicator of any of these outcomes (none = 0 or any = 1). Mediation analyses estimated associations between sexual minority status and SITB outcomes, mediated by exposure to close others' SITB. Bootstrap bias-corrected 95% CIs were calculated with 5000 bootstrap samples. Results: The PLUS cohort included 1202 participants (mean [SD] age, 30.2 [5.1] years; 906 [75.4%] female; 660 [54.9%] heterosexual). The SWS cohort included 1828 participants assessed across 3 waves (mean [SD] age, 26.9 [4.8] years; 1058 [57.9%] female; 1694 [93.1%] heterosexual). Sexual minority participants reported more frequent exposure to close others' SITB (eg, for suicide attempt: PLUS mean [SD], 0.41 [0.49] for sexual minority vs 0.23 [0.42] for heterosexual; P < .001; and SWS mean [SD], 0.28 [0.45] for sexual minority vs 0.14 [0.35] for heterosexual; P < .001) and higher SITB rates (eg, suicidal ideation: PLUS mean [SD], 4.67 [8.19] for sexual minority vs 1.97 [5.57] for heterosexual; P < .001; and SWS mean [SD], 0.35 [0.48] for sexual minority vs 0.13 [0.33]; P < .001) than heterosexual participants. In the PLUS cohort, exposure to close others' suicidal ideation accounted for 53.3% of the association between sexual orientation and past-month suicidal ideation (bootstrap 95% CI, 36.7%-76.0%). In the SWS cohort, exposure to close others' SITB (a composite indicator of exposure to close others' suicide attempt, suicide death, and NSSI) accounted for 46.9% of the association between sexual orientation and past-year NSSI (bootstrap 95% CI, 17.3%-86.3%). Conclusions and Relevance: Findings from this study of 2 nationally representative cohorts of young adults suggest that exposure to close others' SITB may partially explain sexual orientation disparities in SITB. Findings underscore the need for further research into psychosocial mechanisms that may propagate SITB risk following exposure to close others' SITB in vulnerable populations.