Nordsletten and colleagues1 report on the first study looking at assortative mating and psychiatric disorders in a representative population sample (of over 700 000). Compared with the general population, the odds of having a partner who also suffers from a mental health problem – both within and across disorders – were significantly elevated: cross-assortative mating was approximately 0.15 for bipolar disorder, 0.36 for substance misuse, and over 0.40 for attention-deficit hyperactivity disorder, autism spectrum disorder (ASD) and schizophrenia. Overall, having one of these disorders was associated with an approximately two- to threefold increase in the odds of having a mate with the same or an alternative mental health condition. Interestingly and importantly, such cross-assortative mating was not found for a range of physical health conditions, including diabetes, rheumatoid arthritis and multiple sclerosis.