Analysis of 15 million people shows psychiatric disorders are often shared by partners across generations

Mental health may play a bigger role in shaping romantic relationships than previously believed, according to new research involving almost 15 million people across Europe and Asia.

The study, published in Nature Human Behaviour, suggests that people diagnosed with psychiatric disorders are significantly more likely to marry or partner with someone who has the same condition.

Researchers analysed records from Taiwan, Denmark and Sweden, spanning nearly a century and covering nine major psychiatric disorders, including depression, anxiety, anorexia and attention deficit hyperactivity disorder (ADHD). They found consistent patterns across countries, cultures and generations.

The findings reveal that couples tend to “match” on psychiatric diagnoses regardless of cultural background or health care changes over the past 50 years. This phenomenon, known as assortative mating, was observed in every period examined, from the 1930s through to the 1990s.

Rates of shared diagnoses slightly increased with each passing decade, particularly in cases of substance abuse disorders. The researchers note that while improvements in psychiatric treatment have altered how conditions are managed, they have not reduced the tendency for people with the same diagnosis to form partnerships.

The implications extend beyond the couples themselves. Children born to two parents with the same psychiatric condition were found to be twice as likely to develop the same disorder, according to the study.

While the analysis does not establish causation — meaning it cannot determine why people with similar mental health conditions tend to partner — it highlights the complex interplay between shared life experiences, social environments and inherited risk.

The sheer scale of the dataset is unprecedented. By examining national health registries and census data, researchers were able to track patterns across multiple generations and compare results in societies with very different cultural norms and medical systems.

“These results show that mental health is not just an individual matter — it has a strong social dimension that shapes family formation and intergenerational outcomes,” said the study’s authors.

The researchers caution that their findings should not be interpreted as evidence of inevitability. While the likelihood of partners sharing a psychiatric diagnosis is higher than random chance, many couples do not follow this pattern. Furthermore, the elevated risks to children are statistical averages, not certainties for individuals.

Nevertheless, the study adds to a growing body of evidence about the social clustering of mental health conditions. It also raises important questions for public health, particularly around prevention and support for families in which both parents face similar challenges.

Campaigners for mental health awareness welcomed the study’s insights. They stressed, however, that the findings must not be used to stigmatise individuals with psychiatric conditions or their families. Instead, they said the research highlights the need for better support systems, not only for patients but also for their partners and children.

By demonstrating that psychiatric disorders can influence not just individual outcomes but family structures over generations, the research opens new avenues for understanding the broader societal impact of mental health.