The topic of assortative (nonrandom) mating might seem esoteric or even salacious. For example, in lectures you have to point out to students that random mating is not about promiscuity. In this issue of JAMA Psychiatry, Nordsletten and colleagues1 report the first general population study to date of assortative mating for psychiatric disorders, which may help to solve 3 puzzles in psychiatric genetics: Why are psychiatric disorders so highly heritable when they are associated with reduced fecundity? Why are some psychiatric disorders so much more highly heritable than others? Why is there so much genetic comorbidity across psychiatric disorders?
Plomin R, Krapohl E, O’Reilly PF. Assortative Mating—A Missing Piece in the Jigsaw of Psychiatric Genetics. JAMA Psychiatry. 2016;73(4):323-324. doi:10.1001/jamapsychiatry.2015.3204