DATE: October 10, 2026 at 12:00PM
SOURCE: PSYPOST.ORG
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TITLE: Family background may explain much of the mental health gap tied to sexual orientation, twin studies suggest
New research indicates that a large portion of the mental health differences between non-heterosexual and heterosexual individuals might be rooted in shared family background rather than social stigma alone. When non-heterosexual people were compared with their own heterosexual siblings and twins, the mental health gap shrank by about half, and by roughly two-thirds among identical twins. The findings were published in Psychological Medicine.
On average, people who identify as gay, lesbian, or bisexual report higher rates of anxiety, depression, and other mental health difficulties compared to heterosexual people. The most common explanation for this gap is Sexual Minority Stress Theory, which proposes that the excess social stress faced by sexual minorities, such as discrimination, bullying, and systemic stigma, is the primary driver of their worse mental health outcomes.
Supporting evidence includes studies linking experiences such as victimization to distress. For example, a study covered by PsyPost in 2023 indicated that higher levels of same-sex attraction were linked to psychological distress, a relationship that was partly explained by experiences of victimization.
Other factors, however, might also play a role in these disparities. Mental health problems and human temperaments, such as a tendency to experience negative emotions, are strongly influenced by genetics. These factors emerge early in life, often before sexual orientation becomes apparent. The research, led by Péter Przemyslaw Ujma of Semmelweis University, sought to test whether the association between sexual orientation and mental health might actually reflect these shared familial causes.
Genetically informed studies, which compare non-heterosexual people with their own heterosexual brothers and sisters, have produced conflicting results on whether these disparities stem from minority stress or from shared family genetics and upbringing. For instance, an early 1999 study comparing identical male twin pairs found that gay men still reported higher rates of suicidal thoughts than their heterosexual twin brothers, suggesting family background alone did not explain the disparity.
On the other hand, a 2011 twin study found evidence that shared genetic and environmental background factors partly accounted for the higher rates of depression seen in non-heterosexual people. These conflicting outcomes directly prompted the current authors to synthesize the full body of evidence into one comprehensive analysis.
Ujma and his colleagues conducted a systematic multilevel meta-analysis, a statistical technique that combines the results of multiple independent studies to identify overall trends. The authors searched academic databases for English-language studies in which twins or non-twin siblings reported on both their sexual orientation and their mental health, identifying 17 that met their criteria. They set aside one very large Swedish sibling study from the main analysis because it measured sexual orientation through same-sex marriage and reported its results in a different statistical format.
The researchers extracted data from these studies to calculate effect sizes, representing the difference in mental health between heterosexual and non-heterosexual participants, and organized them into three types of comparisons. First, they looked at the mental health gap in the general, unmatched population, meaning all heterosexual people compared to all non-heterosexual people without considering family ties. Second, they compared heterosexual and non-heterosexual individuals across all available pairs of family members, which included a mix of non-twin siblings, fraternal twins, and identical twins. Finally, they isolated comparisons strictly between identical twin pairs where one twin was heterosexual and the other was not.
The results showed a noticeable drop in the mental health disparity as genetic and family relatedness increased. In the unmatched general population, non-heterosexual participants showed worse mental health by about 0.41 standard deviations, a gap typically considered small to moderate. When the researchers controlled for any family relationship, comparing participants to their siblings or twins, the mental health disparity was reduced by 47.5 percent.
Identical twins share nearly 100 percent of their genes and generally experience the same early upbringing, making them the most rigorous test for family-level traits. When comparing a non-heterosexual individual specifically to their identical heterosexual twin, the mental health disparity dropped by 65.7 percent.
Although this reduction was larger than the one for family members in general, the difference between the two estimates was not statistically significant, likely because only a handful of studies reported identical twin comparisons. The authors interpret these results as evidence that roughly two-thirds of the population gap reflects familial factors, such as shared genes and upbringing, rather than minority stress.
Including the large Swedish sibling study, which the authors analyzed separately, shrank the estimated reductions to 27.8 percent for family members overall and 53.7 percent for identical twins.
The identical twin analysis also showed that the gap did not disappear entirely. Non-heterosexual identical twins still exhibited higher rates of mental health symptoms than their heterosexual twins, meaning roughly one-third of the disparity stems from factors the twins do not share. The authors describe sexual minority stress as one candidate explanation for this remaining gap, alongside other possibilities, such as differences in the life paths of non-heterosexual and heterosexual people. More broadly, they argue that much of the disparity has been wrongly attributed to minority stress and that their results partly falsify the theory.
“The key takeaway is that shared familial factors may account for a substantial portion of mental health disparities associated with sexual orientation,” Yiwen Wang, an assistant professor of sociology at the University of Central Florida who was not involved in the research, told PsyPost. “However, accounting for familial background reduces these disparities but does not eliminate them. The study provides an important complement to the minority stress literature by highlighting familial sources of mental health disparities that have received comparatively less attention. I would view these findings as complicating, rather than overturning, minority stress theory.”
“One thing I would caution against is interpreting these findings as evidence that minority stress does not matter,” Wang added. “Accounting for familial factors reduces the disparities, but it does not tell us exactly what mechanisms are responsible for that reduction. Importantly, a meaningful mental health disparity remains even among identical twins.”
As with all research, there are a few things to keep in mind regarding these findings. The authors detected borderline publication bias in the population estimates, meaning the starting mental health gap might be slightly inflated. The studies included in the meta-analysis varied widely in how they defined sexual orientation and which demographic groups they included. The mental health measures and results also differed considerably from study to study, which prevented the researchers from drawing specific conclusions about individual disorders like anxiety or depression in isolated populations.
“The genetically informed design is a notable strength, and the overall pattern is compelling,” Wang noted. “I would be more cautious about the magnitude of the estimates and their causal interpretation, given substantial heterogeneity across studies and the relatively limited evidence from identical twin comparisons.”
Another limitation is that the analyses could not cleanly separate genetic causes from shared environmental causes. The authors suggest the larger reduction among identical twins points toward genetic factors, though the difference between the identical-twin and broader family estimates was not statistically significant.
In addition, because identical twins who differ in sexual orientation are relatively rare, the sample sizes for the strict identical twin comparisons were small, meaning the statistical estimates for that specific group have a wider margin of error. The authors recommend that future studies use highly standardized clinical measures of mental health and prioritize gathering data on both regular siblings and identical twins to build a more precise picture of these dynamics.
“I would like to see studies combine genetically informed designs with direct, longitudinal measures of discrimination, stigma, and other minority stressors,” Wang said. “That could help us better understand how family background and social experiences work together to shape mental health, rather than treating them as competing explanations.”
The study, “How much is sexual minority stress confounded with familial causes? A systematic multilevel meta-analysis,” was authored by Péter Przemyslaw Ujma, John D. Haltigan, and J. Michael Bailey.
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