Measuring Quantitative Autism Traits in Families Using the Social Responsiveness Scale: Informant Effect or Intergenerational Transmission?

Background:

Autism spectrum disorders (ASDs) have a high degree of heritability, but there is still much debate about specific causal genes and pathways. To gain insight into patterns of transmission, research has focused on the relatedness of quantitative autism traits (QAT) between family members, mostly using questionnaires. Yet, different kinds of bias may influence research results.

Objectives:

To examine possible informant effects in an ASD family study using the Social Responsiveness Scale (SRS) as a QAT measure, and, taking these into account, assess possible intergenerational transmission of QAT.

Methods:

We used multiple informant data retrieved via the Social Responsiveness Scale from 170 families with at least one member with ASD. Using intra class correlations (ICCs) and mixed model analyses we investigated inter-informant agreement and differences between parent and teacher reports on children and between self- and other-reports on adults. Using structural equation modelling (SEM) we investigated the relatedness of QAT between family members in ASD families.

Results:

Parent-teacher agreement for social responsiveness was modest (ICC total sample = .55), but poor for children with ASD (ICC = .06-.09). Agreement between parents was moderate to strong for affected (ICC = .52) and unaffected (ICC = .80) children. Agreement between self- and other-report in adult men was good (ICC = .70), but only moderate in women (ICC = .57). Agreement did not differ between adults with and without ASD. While accounting for informant effects, our SEM results corroborated the assortative mating theory and the intergenerational transmission of QAT from both fathers and mothers to their offspring. In a post-hoc analysis, however, this association appeared to be insignificant from fathers to their affected offspring (β=.03, p=.880).

Conclusions:

Since we demonstrated that the inter informant agreement varies depending on the diagnostic status of the participants, we state that the SRS, and possibly also other questionnaires, should be used cautiously when researching familial correlations and transmission of QAT in clinical populations. Furthermore, the the context of the use of the questionnaire (screening vs diagnostic assessment; family research with risk of contrast effect) may influence the results. Our findings also support intergenerational transmission of QAT as measured by the SRS.