In Denmark, as well as in the United States, an individual’s sexual orientation identity is not recorded in death certificates. This greatly limits routine administrative surveillance of suicide mortality risk among lesbian, gay, and bisexual individuals, a subpopulation with known elevated risk for suicide attempts [1–6, 8–15]. This administrative limitation also affects the current study: we could not directly measure sexual orientation identity, but were forced to rely on registered domestic partner status as a proxy for minority sexual orientation identity. Nevertheless, our findings substantiate concerns that the elevation in risk for suicide attempts observed internationally among homosexual and bisexual men [5, 6, 8, 10, 11, 13, 14] is paralleled by a greatly higher risk for suicide mortality among men who are likely to be gay or bisexual. Comparisons of suicide mortality rates between Danish men with positive RDP histories versus those with positive histories of heterosexual marriage revealed an eightfold greater age-adjusted risk for death by suicide among the RDP group. While the numbers of incident suicides in Danish men in RDP relationships were small, reducing precision, this elevation in risk nonetheless appears to be present across the lifespan. Whether this finding extends to all men with minority sexual orientation is currently unanswerable given the limits of available mortality data. However, our findings support longstanding concerns that suicide is a critical mental health issue for the gay men and bisexual men [2, 32].
In marked contrast, we failed to observe a similar elevation in risk for suicide mortality among women who are likely to be lesbian or bisexual. The reason why sexual orientation appears linked to suicide mortality in men, but not to the same extent in women, with histories of being in same-sex registered domestic partnerships (RDPs) is unclear. Both gay men and lesbians in same-gender relationships experience considerable cultural antipathy toward same-sex marriage and domestic partnerships, even where they are legally endorsed . While attitudes toward homosexuality are more tolerant in Northern Europe than in the United States , heterosexual marriage remains the ideal in Denmark . Both lesbians and gay men also frequently experience anti-gay stigma and consequent adversity in their daily lives [36, 37], the presumed mechanism that leads to the somewhat elevated risk for psychological morbidity that has been observed in this population . In particular, both lesbians and gay men compared to their heterosexual counterparts are at higher risk for major depression , an important risk factor for completed suicide . And though the evidence for women is somewhat less compelling, it appears that both lesbians and gay men are at higher risk for lifetime histories of suicide attempts [1–6, 8–15], also a known risk factor for suicide mortality .
But there are other ways in which the lives of lesbians and gay men differ and it may be these factors that are more closely linked to suicide mortality risk. One obvious difference is the impact of the HIV epidemic on gay men’s health . Although the estimated prevalence of HIV infection among men who have sex with men in Denmark (4.8%)  is far lower than estimates in the United States, it may be that some of the increase in suicide risk results from gay men’s experiences with HIV disease either personally or among their partners and friendship networks [43, 44]. Further, a recent study  of all-cause mortality in Denmark found a substantial reduction in mortality risk among men in RDP relationships after the introduction of highly active anti-retroviral therapy (HAART). Future studies might profitably examine the co-occurrence of HIV infection and suicide mortality. Important in this investigation would be a distinction between suicides from before and after HAART introduction, a distinction that may become clearer with additional years of mortality experiences among individuals in RDP relationships. At this junction, however, the gender differences in suicide mortality risk among lesbians and gay men remain unexplained.
We also observed a higher risk for suicide among never married men compared to current or formerly married men but a lower risk for suicide among never married women when compared to current/formerly married women. Never married women, however, were at higher suicide mortality risk than currently married women, consistent with other European studies [45, 46]. Our findings were due to the higher suicide mortality risk among formerly married women, including widowed individuals who represent a well-known higher risk group for suicide .
Results observed here should be considered in the context of four potential study limitations. First, as mentioned earlier, we did not directly measure sexual orientation, but rather used registered partner status as a proxy for minority sexual orientation identity. One consequence is the exclusion of individuals under age 18, the legal age in Denmark for entering RDP status. Also, to the extent that individuals in registered same-sex partnerships differ from lesbian, gay, and bisexual individuals who are not, we may have under or overestimated suicide-related mortality in this subpopulation. Currently, the proportion of same-sex couples in Denmark that legally register their relationship is unknown, but estimates from the United States suggest that only a minority of lesbian, gay, and bisexual individuals, especially men, live in a cohabiting same-sex relationship , and the extent to which these couples are legally registered with governmental agencies when permitted by law is unknown but presumably a much smaller subset of such persons, especially among men . Married individuals, in general, have the lowest risk for suicide mortality . If one assumes that similar protective properties endemic to marriage extend to same-sex couples [25, 50, 51], then we would anticipate that the findings reported here are most likely an underestimate rather than an overestimate of suicide mortality risk among lesbian, gay, and bisexual adults as a whole.
Second, recent findings for all causes of death in Denmark  show that both men and women in registered same-sex partners have a significantly elevated mortality risk when compared to married individuals, but only in the initial years following registration. This finding has been interpreted as suggestive that individuals who are severely ill will be more likely to register, thus biasing estimates in the direction of showing greater mortality linked to sexual orientation where such differences do not actually exist . But whether this is true for suicide as a cause of death is unclear. Further, the assertion of differential selection into RDP status conditional on mortality risk is based on very small sample sizes, particularly for long-term relationships where mortality rates generally remained elevated but did not achieve statistical significance. Low statistical power may have created this pattern of results. Given the newness of the institutionalization of RDPs, it will take several years of accumulating experience to clarify whether selection is a reasonable hypothesis for explaining what was observed in the current study.
Third, errors of misclassification in the allocation of primary cause of death to suicide are always a concern . If these were confounded in some way with registered partner status then this might serve to inflate or deflate our estimates of the relative risk of suicide mortality in this subpopulation. Because we observed elevation in rates among men, but not women, in registered partnerships, we are reassured that this bias, if it exists, was minimal. However, future studies of method of self-injury might clarify the import of this concern.
Finally, we limited our analysis to suicide as a primary cause of death in a single country and did so with minimal information about the deceased individuals. It is possible, future studies that examine suicide as both a primary or contributing cause of death (multiple cause mortality) or suicide mortality in other geographic regions may observe somewhat different results. Also future studies might gainfully explore demographic and behavioral characteristics of gay and bisexual suicide completers.
With the emergence of new administrative forms of relationship status in various states within the United States and in other countries internationally where same-sex marriage or domestic partnerships have been legalized, scientists have a unique opportunity to track the health and mental health correlates of sexual orientation using these administrative databases and to do so over time. In this study, we have used administrative records from Denmark to uncover an unrecognized, but widely anticipated [1–6, 8–15], elevated risk for suicide-related mortality among adult gay and bisexual men.
These results call strongly for the development of suicide prevention programs for gay and bisexual men that target men’s concerns across the lifespan. They also underscore the importance of integrating into our surveillance systems thoughtful measurement of both mental health indicators, including suicide-related morbidity and mortality, and markers of sexual orientation. As an example, currently the Centers for Disease Control and Prevention (CDC) in the United States assesses homosexual behavior in its surveillance of HIV and other sexual transmitted diseases . This is an effort to reduce morbidity and mortality among gay and bisexual men, a vulnerable population for acquiring sexually transmitted diseases. But CDC tracking of suicide mortality is accomplished through the National Violent Death Reporting System  which does not measure markers of sexual orientation, though it does provide information on other social statuses readily available in administrative records such as age, gender, marital status, and race/ethnicity. Better integration of data sources, including use of domestic partnership registries and information on the sexual orientation of marriages in those states and countries where same-sex marriage is legal, might prove beneficial to reducing mental health disparities linked to minority sexual orientation. To date, in the United States, only gay and lesbian adolescents have been labeled as a vulnerable population for suicide morbidity by the US Public Health Service . Our findings strongly suggest a broadening of that focus to adult gay men, at a minimum.