We’ve all heard that opposites attract, but according to science, when it comes to people with mental health disorders, the adage is not quite the case.
A study of almost 15 million people across Europe and Asia revealed people with a psychiatric disorder are more likely to marry someone who has the same condition than to a partner who doesn’t - a pattern which is consistent across generations and cultures.
The findings published in the journal Nature Human Behaviour used data from people in Taiwan, Denmark and Sweden.
It examined the proportion of people in those couples who had one of nine psychiatric disorders: schizophrenia, bipolar disorder, depression, anxiety, attention-deficit hyperactivity disorder (ADHD), autism, obsessive–compulsive disorder (OCD), substance-use disorder and anorexia nervosa.
Although scientists do not have a definitive understanding on what causes people to develop psychiatric disorders, they believe genetics and environmental factors play a part.
Co-author Chun Chieh Fan, a population and genetics researcher at the Laureate Institute for Brain Research, told the science journal Nature: “The main result is that the pattern holds across countries, across cultures, and, of course, generations.”
He added that changes in psychiatric care over the past 50 years have not shifted the trend.
Out of the nine psychiatric disorders only OCD, bipolar disorder and anorexia nervosa showed different patterns across countries. In Taiwan, married couples were more likely to share OCD than couples in Nordic countries.
Researchers separated the data into birth cohorts with ten-year intervals from the 1930s to 1990s. This revealed that the chances of partners sharing a diagnosis increased slightly with each decade, particularly for those with disorders related to substance use.
The study also found that children who have two parents with the same disorder are twice as likely to develop the condition.
The study was observational, which means it could not definitively explain why people with psychiatric disorders often paired up - but researchers have suggested a few explanations.
“Perhaps they better understand each other due to shared suffering, so they attract each other,” Dr Fan told Nature.
He suggests people might be attracted to those who resemble them or that a shared environment could make partners more alike. He added that the societal stigma of having a psychiatric disorder narrows a person’s choice of spouse.
The prevalence of different psychiatric disorders vary in the UK.
In England, about a quarter of people will experience a mental health problem of some kind each year, according to mental health charity Mind.
About 3 per cent of adults experience depression in any given week in England and 6 per cent of people experience generalised anxiety disorder.
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