Non random dating
Cases of schizophrenia, bipolar disorder, autism spectrum disorder, anorexia nervosa, substance abuse, attention deficit hyperactivity disorder (ADHD), obsessive compulsive disorder (OCD), major depressive disorder, social phobia, agoraphobia, and generalised anxiety disorder were identified using standard protocols.
For comparison purposes, cases of Crohn’s disease, type 1 and type 2 diabetes, multiple sclerosis and rheumatoid arthritis were also identified.
First, the proportion of mated pairs in the full case and control samples was summarised.
Correlations were calculated to evaluate the relationship between the diagnostic status of each individual in a couple, first within and then across disorders.
First, shared environment (which would capture effects of partner interactions) appears to play very little role in many psychiatric conditions.
Second, neurodevelopmental conditions are present over the lifespan (i.e., before couples typically meet), which would suggest an assortative mating explanation for the observed similarity for at least these conditions.
For each case (i.e., individuals with a diagnosis), five population controls were identified, matched on age, sex and area of residence.
Mating relationships were identified through records of individual marriages, and through records of individuals being the biological parent of a child.
The authors conclude that the non-random mating they observed may be due to assortative mating for two reasons.
Non-random mating refers to the tendency for partners to be more similar than we would expect by chance on any given trait of interest.
This is straightforward to see for traits such as height and weight, but less obvious for traits such as personality.
These consortia and large individual studies are now achieving the necessary sample sizes to detect the very small effects associated with common genetic variants,.
We’ve known for some time that psychiatric disorders are under a degree of genetic influence, but one puzzle is why estimates of the heritability of these disorders (i.e., the proportion of variability in risk of a disorder that is due to genetic variation) differs across disorders.