3 Mar 2016
March 4, 2016. Results from a new study show that people with psychiatric disorders pair with partners who also have a psychiatric disorder more frequently than would be expected by chance. The results are more than an interesting curiosity, because they might help explain some of the complicated heredity data in mental illness.
The study, published online on February 24 in JAMA Psychiatry, was led by Ashley Nordsletten of the Karolinska Institute in Sweden and included hospital and outpatient psychiatric data from more than 700,000 people.
Nordsletten and colleagues were able to conduct such a large study—which included more than 70,000 people diagnosed with schizophrenia—thanks to Sweden's comprehensive population registers. The study included people who had been diagnosed with at least one of 11 psychiatric disorders as well as people with select non-psychiatric diseases.
For almost every psychiatric disorder, people with that disorder were significantly more likely to have a partner with the same diagnosis compared to the matched controls (i.e., a person with schizophrenia was more likely to have a partner with schizophrenia than a control person was to have a partner with schizophrenia). Intriguingly, there were also strong correlations between different disorders, including between the thought disorders. In particular, people with schizophrenia were more likely to mate with someone with autism compared to their matched controls. For people with non-psychiatric disorders, meaningful spousal correlations were rare.
This study may have profound implications for future psychiatric genetics research—especially for studies that use genetic models that assume random mating. "Our findings suggest that this is not an accurate assumption in many cases, and thus models should allow for the correlation of spouses to avoid biases in heritability estimates," Nordsletten wrote to SRF. (For more details, see the related news story.)—Summer E. Allen.