People diagnosed with a psychiatric disorder are more likely to marry someone who shares the same condition rather than pairing with someone who does not have any disorder at all. This finding stems from an extensive study indicating that such patterns exist across various cultures and generations.
While previous research identified this trend primarily in Nordic countries, it hadn’t been extensively explored outside Europe until now.
The recent study, featured in Nature Human Behaviour, analyzed data from over 14.8 million individuals in Taiwan, Denmark, and Sweden. It focused on couples where at least one partner had one of nine psychiatric disorders: schizophrenia, bipolar disorder, depression, anxiety, ADHD, autism, OCD, substance use disorder, and anorexia nervosa.
Although the exact causes of psychiatric disorders remain unclear, it is believed that both genetic and environmental factors contribute. The research team discovered that if one partner had a psychiatric condition, the other was notably more likely to be diagnosed with the same or a different disorder. According to co-author Chun Chieh Fan, who is a researcher in population and genetics at the Laureate Institute for Brain Research in Tulsa, Oklahoma, spouses were found to share similar conditions more frequently than to have dissimilar ones.
Fan emphasizes that this trend is consistent across countries and cultures and has remained unchanged despite the evolution of psychiatric care over the last five decades.
However, OCD, bipolar disorder, and anorexia nervosa displayed varying patterns depending on the country. For example, couples in Taiwan were more prone to sharing OCD than couples in Nordic regions.
The study categorized participants into birth cohorts spanning from the 1930s to the 1990s in ten-year intervals. It revealed that, generally, the likelihood of partners having a shared diagnosis has slightly increased with each decade, particularly for disorders related to substance use.
What’s behind the trend?
Although the research did not delve into the underlying causes of this trend, Fan proposed three possible explanations. One theory is that people might be drawn to those who are similar to themselves, perhaps because they can relate to each other through shared experiences of suffering.
Another theory suggests that a shared environment might contribute to making partners more alike—a concept known as convergence. Lastly, societal stigma associated with psychiatric disorders could limit an individual’s spouse selection.
Jan Fullerton, a psychiatric geneticist at the University of New South Wales in Sydney, Australia, mentioned that social and environmental stressors might lead to new diagnoses in previously unaffected partners, especially if they had underlying yet undiagnosed symptoms.
