1. A prominent study carried out in 2001 in the Netherlands produced some disturbing results. Same-sex sexual behavior and psychiatric disorders: findings from the Netherlands Mental Health Survey and Incidence Study (NEMESIS) by Sandfort TG, de Graaf R, Bijl RV and Schnabel P (Arch Gen Psychiatry. 2001 Jan;58(1):85-91. pdf here) showed that (and I quote from the abstract)

    Even in the Netherlands where homosexuality is much more widely condoned and even supported, there are still strikingly different mental health outcomes for homosexuals.

    Psychiatric disorders were more prevalent among homosexually active people compared with heterosexually active people. Homosexual men had a higher 12-month prevalence of mood disorders (odds ratio [OR] = 2.93; 95% confidence interval [CI] = 1.54-5.57) and anxiety disorders (OR = 2.61; 95% CI = 1.44-4.74) than heterosexual men. Homosexual women had a higher 12-month prevalence of substance use disorders (OR = 4.05; 95% CI = 1.56-10.47) than heterosexual women. Lifetime prevalence rates reflect identical differences, except for mood disorders, which were more frequently observed in homosexual than in heterosexual women (OR = 2.41; 95% CI = 1.26-4.63).

    The paper itself makes this comment:

    It is unclear to what extent findings from this Dutch study can be generalized to other cultures or nations. Compared with other Western countries, the Dutch social climate toward homosexuality has long been and remains considerably more tolerant. To the extent that the level of social acceptance of homosexuality induces differences in mental health status in relation to homosexuality, the observed differences might be greater in other Western countries than in the Netherlands.