How much is sexual minority stress confounded with familial causes? A systematic multilevel meta-analysis.

BACKGROUND: Compared with heterosexual persons, non-heterosexual persons have worse mental health. Sexual Minority Stress Theory (SMST) explains the disparity as resulting from stigma and discrimination. To the extent that heterosexual genetic relatives reared with non-heterosexual persons also have worse mental health, SMST is falsified. We conducted a systematic meta-analysis of studies containing family-genetic comparison data to interrogate the empirical support for SMST. METHOD: We systematically identified 17 empirical studies in which twins or non-twin siblings reported on both their sexual orientation and their mental health. Subsequently, we conducted a multilevel meta-analysis, focusing on the degree to which any sexual orientation disparity in mental health diminished with genetic relatedness. RESULTS: Most of the mental health disparities between non-heterosexual and heterosexual persons were eliminated after controlling for family-genetic factors. CONCLUSIONS: The mental health disparity between non-heterosexual and heterosexual persons is reduced by up to two-thirds once familial background factors are accounted for by comparing monozygotic twins discordant for sexual orientation. This suggests that shared familial causes, and not minority stress, are the most important causes of mental health disparities in non-heterosexual persons.