The Broader Autism Phenotype in Parents of Children with ASD: A Systematic Review of Studies Reporting the Association Between Parent and Child Phenotype

Background:

Broader autism phenotype (BAP) is elevated among parents of children with autism spectrum disorder (ASD). Identifying BAP in parents may help create subgroups of children with ASD that can improve efficiency in etiologic research. However, the literature on parental BAP is heterogeneous. Sources of heterogeneity include different measurement tools, varying informant types, which parent is assessed (mother, father, both), the source of the sample/population, and sample size. This variance has prevented clear understanding of the proportion of children with ASD that have parents with BAP and whether parental BAP impacts child ASD phenotype.

Objectives:

We aim to systematically review the literature to highlight and better understand heterogeneity of reported percentage of BAP in parents of children with ASD. Our secondary goal is to synthesize the literature on the association between parental BAP and child ASD phenotype. Better understanding of this relationship will be useful in identifying endophenotypes (specific traits genetic in origin that can parse heterogeneity) that can be used to refine etiologic analyses.

Methods:

We systematically searched Pubmed and Scopus databases in August 2016. Key search terms included ‘broader autism phenotype’, ‘quantitative autistic traits’ ‘parents’, ‘relatives’, and slight derivations of those phrases. Two independent reviewers examined 477 papers by title and abstract, resulting in a full text review of 97 papers. Studies were excluded if they did not measure BAP in parents of children with ASD or did not present dichotomized parental BAP status (BAP+ or BAP-).

Results:

Fifty-seven papers were identified that met criteria. Identified papers used eight different measurement tools, four types of informants, and three types of respondents. Sample sizes ranged from 4 to 3299. Thirty-nine papers reported proportion of parents with BAP, ranging from 3% to 73%. In most studies, the proportion of fathers with BAP was higher than mothers. The Family Health Interview was the most common measure and had the widest range in percentages, which may illustrate changes in the instrument over time or its use across clinical and population based samples. When sample size increased, the proportion of parents with BAP was less than in smaller samples, which may be a factor of sample population (clinic or population based) or difference in the type of measurement tools used depending on sample size. Fourteen studies assessed how parent BAP is associated with child ASD phenotype. These studies showed a relationship between parent restrictive and repetitive behavior and interests (RRBI) and child rigidity. There was also a positive association between parental BAP scores and child scores on ASD screeners. Father’s BAP tended to have a stronger association with child phenotype as compared to maternal BAP.

Conclusions:

BAP is prevalent in parents of children with ASD and there may be an association between BAP in parents and child ASD phenotype. Using BAP as a way to subgroup ASD may improve the efficiently of etiologic studies. Thoughtful consideration should be given when interpreting results of parental BAP studies, as sample type, measurement tool, and parent type may all play a role in effecting estimates.