A groundbreaking international study has revealed that individuals with psychiatric disorders are significantly more likely to marry someone with the same condition than to partner with someone without it, a trend that persists across cultures and generations. The findings, published today in Nature Human Behaviour, draw on data from more than 14.8 million people in Taiwan, Denmark, and Sweden.
The research examined couples in which at least one partner had one of nine psychiatric conditions, including schizophrenia, bipolar disorder, depression, anxiety, ADHD, autism, obsessive–compulsive disorder (OCD), substance-use disorder, and anorexia nervosa. Researchers found that when one partner carried a diagnosis, the other was significantly more likely to have the same or another psychiatric disorder, with the tendency to match diagnoses exceeding the likelihood of having different conditions.
“The main result is that the pattern holds across countries, across cultures, and, of course, generations,” said co-author Chun Chieh Fan, a population and genetics researcher at the Laureate Institute for Brain Research in Tulsa, Oklahoma. The study also found that this trend has persisted over decades, even as psychiatric care has evolved over the past 50 years. Only OCD, bipolar disorder, and anorexia nervosa showed some variation across countries, with, for instance, Taiwanese couples more likely to share OCD than their Nordic counterparts.
The study explored several possible explanations for the phenomenon. One theory is that people may be attracted to partners who resemble them, creating a shared understanding through common experiences of mental health challenges. Another explanation is the “convergence” effect, where shared environments may influence partners to develop similar conditions. Finally, societal stigma may restrict the pool of potential partners, indirectly increasing the likelihood of forming relationships with someone who has a similar psychiatric profile.
The implications of these findings extend to future generations. Children with two parents affected by the same disorder were found to be twice as likely to develop the condition themselves compared to children with only one affected parent. This highlights the combined impact of genetics and environment on mental health.
Experts emphasize the importance of the research for public health and genetic counseling. “More research is needed before psychiatrists change how they communicate the genetic risks of mental-health disorders to patients,” said William Reay, a statistical geneticist at the Menzies Institute for Medical Research in Hobart, Australia. Molecular geneticist Moinak Bannerjee added that the study could help couples understand genetic risks they might otherwise be unaware of, providing valuable guidance for informed family planning.
By documenting this pattern across millions of people and multiple countries, the study offers a rare global perspective on psychiatric assortative mating, underscoring the interplay of genetics, environment, and societal factors in mental health.