Assortative Mating and Increase in Prevalence and Severity of Autistic Spectrum Disorder in Children—A Systematic Review

<b>Background/objectives:</b> The prevalence of autistic spectrum disorder has been increasing rapidly in the world population and the cause of this increase is unknown. Autistic spectrum disorder is an important cause of social, communication and specific learning difficulties in children. Assortative mating may increase the genetic burden leading to manifestation of polygenic diseases affecting mental health in the offspring. Correlation of scores in the social responsiveness scale (SRS), which is used to quantify autistic spectrum disorder features, between spouses, has been used as indicator of phenotypic assortative mating. We investigated whether assortative mating is involved in increased severity of autism spectrum disorder in the offspring. <b>Methods:</b> All studies reporting on investigation of assortative mating in relationship to autistic spectrum disorder were included. Information sources were PubMed, EMBASE and the Cochrane Library. Results were synthesized by entering correlation analyses of results of the SRS conducted in spouses in a meta-analysis. A sub-group analysis was performed comparing spouses with offspring with diagnosed autistic spectrum disorder to spouses without. Prevalence of autistic spectrum disorders in children in countries with and without predominant assortative mating was compared. <b>Results</b>: A total of 14 investigations of assortative mating including 9914 spouse pairs were included. In total, 8 studies (4641 spouse pairs) reported intra-class correlation (ICC) or Spearman's correlation coefficients between spouses' SRS scores. There was a significant correlation of SRS scores in studies using ICC or Spearman's correlation with a pooled coefficient = 0.37. Spouse pairs (n = 401) with offspring diagnosed with autistic spectrum disorder had a pooled ICC coefficient which was 0.278 (95% CI 0.08 to 0.46), significantly lower than spouse pairs without (n = 1525): 0.40 (95% CI 0.35 to 0.46). Higher scores in SRS of both spouses were associated with higher scores and more autism diagnoses in offspring. Pooled prevalence of autistic spectrum disorder in children in countries where assortative mating is most common was 63.1 per 10,000 of population and in countries without it was significantly lower with 14.1 per 10,000 of population. <b>Conclusions</b>: There is evidence of assortative mating according to social responsiveness scale score which correlates significantly in spouse pairs with and without children with autistic spectrum disorder. In countries where assortative mating is predominant, a higher prevalence of autism spectrum disorder in children is found compared to countries without.