Sexual orientation and suicidality: a co-twin control study in adult men

Several recent studies have found a higher lifetime prevalence of suicide attempts in homosexual males compared with heterosexual control subjects or population rates. These studies used either convenience samples, most without controls, or population-based samples in which confounding factors such as depression and substance abuse were not measured.

This study used twins from the population-based Vietnam Era Twin Registry, Hines, Ill. An analytic sample of 103 middle-aged male-male twin pairs from the registry was identified in which one member of the pair reported male sex partners after age 18 years while the other did not. Four lifetime symptoms of suicidality as measured by the Diagnostic Interview Schedule were analyzed: thoughts about death, wanting to die, thoughts about committing suicide, and attempted suicide. A composite measure of reporting at least one suicidality symptom was also assessed.

Same-gender sexual orientation is significantly associated with each of the suicidality measures. Unadjusted matched-pair odds ratios follow: 2.4 (95% confidence interval [CI], 1.2 - 4.6) for thoughts about death; 4.4 (95% CI, 1.7 - 11.6) for wanted to die; 4.1 (95% CI, 2.1 - 8.2) for suicidal ideation; 6.5 (95% CI, 1.5 - 28.8) for attempted suicide; and 5.1 (95% CI, 2.4 - 10.9) for any of the suicidal symptoms. After adjustment for substance abuse and depressive symptoms (other than suicidality), all of the suicidality measures remain significantly associated with same-gender sexual orientation except for wanting to die (odds ratio, 2.5 [95% CI, 0.7 - 8.81).

The substantially increased lifetime risk of suicidal behaviors in homosexual men is unlikely to be due solely to substance abuse or other psychiatric comorbidity. While the underlying causes of the suicidal behaviors remain unclear, future research needs to address the inadequacies in the measurement of both sexual orientation and suicidality in population-based samples.