ASSORTATIVE MATING

Assortative mating: does it increase the prevalence of autism?

Assortative mating is the social dynamic when persons with similar characteristics, likes, dislikes, and traits, tend to choose each other in close relationships, such as marriage. Research has pointed to a possible role of assortative mating in increasing the prevalence of autism.

Reports of an increasing autism rate worldwide in recent years have raised public health as well as individual parenting concerns. Apart from theoretical knowledge, there is practical interest in knowing the causes of autism in order to engage in and apply optimal responses that could improve the well-being of persons born with autism.

Compared to the general population, assortative mating occurs more frequently in neurodiverse and psychiatric populations including autism spectrum disorder, schizophrenia, and ADHD. Partners who similarly carry those latter conditions are likely to share an abundance of similar genetic variants linked to their condition. Since genetic factors are established as the largest predictor or cause of autism and other neurodiverse conditions, it is expectable that couples with similar genetic variants linked to autism would have an increased likelihood of producing offspring with autism or autism traits. If such is the case, this would potentially result in a relative increase over time in the autism rate in a given population.

Confounding that trend, though, is another research observation – among persons with autism, the rate of fecundity defined as the ability of an individual or population to produce offspring is notably lower than in the general population. (Notably, a lower- than-expected fecundity rate has also been observed among other neurodiverse groups where the rate of assortative mating has also been observed to be higher than expected.) Even in the context of high heritability or genetic transfer, a low fecundity rate when autistic individuals mate would attenuate a possible increased autism prevalence rate.

Autism is established as a complex condition, featuring a range of abilities, talents, and strengths as well as impairments and developmental delays among affected persons. There are references in the literature to variations indicated by “low versus high functioning”, and terms such as “profound autism” indicating persons requiring considerably more support than other autistics, as well as “borderline autism” indicating instances where the individual manifests several indicators of autism yet does not meet the full criteria for a clinical determination of autism. These variations are determined by multiple genes and the combinations of these genes.

In light of that complexity as well as the low fecundity rate among autistic couples, assortative mating can impact not only the rate of autism but also the resulting symptom profile of the autistic offspring. How veridical are these assumptions remains to be known. Nevertheless, knowledge and insight regarding the genetic and possible societal implications, desirable or not, of assortative mating among autistic groups may provide direction and clarity when autistic couples contemplate and make decisions in their choice of a life partner.

References:

Wouter J Peyrot et al. JAMA Psychiatry. 2016, 73 (11). 1189-1195. Exploring boundaries for the genetic consequences of assortative mating for psychiatric traits.

Power, RA et al. JAMA Psychiatry, 2013; 70(1): 22-30. Fecundity of patients with Schizophrenia, Autism, Bipolar Disorder, Depression, Anorexia Nervosa, or Substance Abuse vs Their Unaffected Siblings.