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Although same-sex marriage has not been legalized nationally in Japan, various municipal governments have independently introduced partnership certification systems for same-sex couples. However, a nationwide online survey conducted by researchers at the University of Tsukuba found that living in a municipality with such a system was not associated with better mental health among individuals belonging to the sexual minority.

Tsukuba, Japan—Previous international studies have shown that sexual and gender minorities (SGM) experience higher rates of mental health problems than cisgender heterosexual individuals (i.e., those whose gender identity aligns with their sex assigned at birth), largely because of social stressors such as stigma and discrimination. Research in countries where same-sex marriage has been legalized shows that legalization has contributed to improvements in mental health among SGM individuals.

In contrast, Japan has yet to recognize same-sex marriage nationally. Multiple municipal governments have introduced partnership certification systems to provide civil recognition of relationships for SGM residents. However, these systems do not confer a legal status equivalent to marriage.

Therefore, this study used cross-sectional data from a nationwide online survey of Japanese citizens aged 18 years and older that was conducted in 2022. The survey examined whether mental health outcomes among SGM individuals differed depending on whether they lived in municipalities with partnership certification systems. Psychological distress and self-reported suicidal ideation were used as indicators of mental health.

The results showed that SGM individuals reported significantly higher levels of psychological distress and suicidal ideation than cisgender heterosexual individuals. After adjusting for individual- and municipality-level factors, no difference in psychological distress was found between individuals living in municipalities with partnership certification systems and those living in municipalities without such systems. Surprisingly, suicidal ideation was reported more frequently among those living in municipalities with such systems.

Consistent with previous international research, this study shows that SGM individuals in Japan experience greater rates of mental health distress. However, municipal partnership certification systems alone were not associated with improved mental health outcomes. Because this study was cross-sectional, the findings do not establish causality. Nevertheless, they highlight the need for broader, more comprehensive policies and civil rights protections beyond partnership certification systems to better support the mental health of SGM individuals in Japan.

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This study was supported by Grant-in-Aid for Scientific Research (KAKENHI) 22H03325/23K24583 from the Japan Society for the Promotion of Science.

Original Paper

Title of original paper:

Association Between Same-Sex Partnership Certificate Schemes and Mental Health in Sexual and Gender Minority Adults: Nationwide Cross-sectional Study in Japan

Journal:

BMJ open

DOI:

10.1136/bmjopen-2025-106055

Correspondence

Associate Professor MIYAWAKI Atsushi
Institute of Medicine, University of Tsukuba

Related Link

Institute of Medicine