Causes of assortative mating in mental disorders

Assortative mating (AM) is defined as the correlation between matting partners with respect to a phenotype. In humans, AM has been described for different types of anthropometric, socioeconomic, and behavioral traits including mental disorders. Partner's similarity with respect to a phenotype can be due to couples’ attraction based on that phenotype (direct assortment), based on a secondary phenotype that is highly correlated to it (indirect assortment), or even as a consequence of phenotypic convergence among partners due to the environmental factors that partners share during their cohabitation. Disentangling the nature of the observed AM for a phenotype is essential to understand its genetic consequence. Assortative mating for heritable traits induces a correlation of genetic values among partners, whereas assortment on environmental factors (e.g. social homogamy) shared by partners does not. The correlation of the genetic values of the partners in turn affects the amount of genetic variance of the trait assorted on, which has implications on its heritability. To disentangle the underlying causes of AM in mental disorders, we use a population-wide analysis of the Danish population (XXX individuals or pairs). We will compare different types of correlation in pair of relations (e.g., spouses, in-laws, co-in-laws, etc.) to distinguish between assortative mating due to shared genetic factors and assortative mating driven by environmental and social factors in nine mental disorders: substance use, schizophrenia, depression, bipolar, ADHD, autism, phobia, anxiety, and anorexia. We observed different extend of correlation between pairs of relatives which is the key to distinguishing between assortative mating due to shared genetic factors and assortative mating driven by environmental and social factors. Our findings will provide valuable insights into the mechanisms underlying AM in mental disorders.