People with psychiatric disorders appear more likely to be attracted to others with mental illness. And not only is this “assortative mating” found across many different types of mental illnesses, the correlations between spouses sharing psychiatric disorders is much higher than spouses with similar personalities or height, according to research published in JAMA Psychiatry.
Ashley Nordsletten, PhD, from the Department of Clinical Neuroscience in Sweden and colleagues found that the correlation between spouses for psychiatric disorders was extremely high: while correlation between spouses for physical traits such as height and weight was only approximately 0.20, and the correlation between spouses for personality was only 0.10, spouse tetrachoric correlations were greater than 0.40 for attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and schizophrenia.
Substance abuse was the next highest spouse correlation ranging from 0.36-0.39. For other disorders, including affective disorders, assortative mating was significant but less substantial, ranging from 0.14-0.19.
In contrast, the researchers found no such spousal correlation for the non-psychiatric conditions they examined, including Crohn’s disease, type 1 and type 2 diabetes mellitus, multiple sclerosis, or rheumatoid arthritis.
This research represents the first general population study of assortative mating in psychiatric disorders.
In an accompanying editorial, Robert Plomin, PhD, from the Institute of Psychiatry, Psychology, and Neuroscience at King’s College London and colleagues explained that this research may help to answer 3 key questions in psychiatric genetics:
1. Why are psychiatric disorders so highly heritable when they are associated with reduced fecundity?
2. Why are some psychiatric disorders so much more highly heritable than others?
3. Why is there so much genetic comorbidity across psychiatric disorders?
In order to quantify the nature and extent of assortative mating in psychiatric conditions, Dr Nordsletten and colleagues examined data from 707 263 participants (45.7% women) with a psychiatric disorder of interest and their spouses using the Swedish population registers. Using other registers to track couples via their children, the researchers were able to measure assortative mating levels within and between 11 psychiatric disorders, including ADHD, ASD, schizophrenia, bipolar disorder, major depression, generalized anxiety disorder, agoraphobia, social phobia, obsessive-compulsive disorder, anorexia, and substance abuse.