Non-random mating patterns within and across education and mental and somatic health.

Partners resemble each other in health and education, but studies usually examine one trait at a time in established couples. Using data from all Norwegian first-time parents (N = 187,926) between 2016-2020, we analyse grade point average at age 16, educational attainment, and medical records of 10 mental and 10 somatic health conditions measured 10 to 5 years before childbirth. We find stronger partner similarity in mental (median r = 0.14) than in somatic health conditions (median r = 0.04), with ubiquitous cross-trait correlations in mental health (median r = 0.13). High grade point average or education is associated with better partner mental (median r = -0.16) and somatic (median r = -0.08) health. Elevated mental health correlations (median r = 0.25) in established couples indicate convergence. Analyses of siblings and in-laws suggest that health similarity is influenced by indirect assortment based on related traits. Adjusting for grade point average or education reduces partner health correlations by 30-40%. These findings have implications for the distribution of risk factors among children, genetic studies, and intergenerational transmission.