Couples can tend to be more alike in some characteristics than might otherwise be expected by chance. Some literature suggests this so-called "marital resemblance" may be present for a range of psychiatric features. If present, nonrandom mating, which is the tendency of people with similar characteristics to marry or procreate, could have implications for understanding the transmission and persistence of psychiatric illnesses. In a new study published online by JAMA Psychiatry, Ashley E. Nordsletten, Ph.D., of the Karolinska Institutet, Sweden, and coauthors sought to quantify the nature and extent of nonrandom mating within and across a broad range of 11 major psychiatric disorders.

The study used Swedish population registers and participants were Swedish residents with a psychiatric diagnosis. The authors report that nonrandom mating was widespread in psychiatric populations both within and across psychiatric disorders. "This phenomenon, which is not observed in nonpsychiatric populations, may hold important implications for how we understand the familial transmission of these conditions and the ubiquity of comorbidity and complex symptoms in clinical populations," the study concludes.

Research: Patterns of Nonrandom Mating Within and Across 11 Major Psychiatric Disorders, Ashley E. Nordsletten, PhD; Henrik Larsson, PhD; James J. Crowley, PhD; Catarina Almqvist, MD, PhD; Paul Lichtenstein, PhD; David Mataix-Cols, PhD, JAMA Psychiatry, doi:10.1001/jamapsychiatry.2015.3192, published online 24 February 2016.

The study includes conflict of interest and funding/support disclosures. Please see the article for additional information, including author contributions and affiliations, financial disclosures, funding and support, etc.

Editorial: Assortative Mating - A Missing Piece in the Jigsaw of Psychiatric Genetics, Robert Plomin, PhD; Eva Krapohl, MSc; Paul F. O'Reilly, PhD, JAMA Psychiatry, doi:10.1001/jamapsychiatry.2015.3204, published online 24 February 2016.