Social Responsiveness: a Quantitative Intermediate Phenotype in Parents of Children with An Autism Spectrum Disorder

Background: Although heritability of Autism Spectrum Disorders (ASD) is up to 90%, finding specific genetic causes has proven to be very difficult. There is genetic heterogeneity (e.g. copy number variants, single nucleotide polymorphisms). Though in some cases dominant genetic effects operate, additive effects seem more common. This means that, on average, both parents may contribute to the risk for ASD without having ASD themselves (Steyaert & De la Marche, 2008). Carrying such a risk factor might result in subclinical traits of ASD. The Social Responsiveness Scale (SRS) (Constantino et al., 2003) has proven to reliably measure traits of ASD in a quantitative way in the general as well as in the clinical population.

Objectives: To assess if parents of a child with ASD show traits of ASD, in-between general population adults and adults with ASD.

Methods: We requested general population (GP) adults, parents of children with ASD (ASD-P) and adults with ASD (ASD) and their partners or parents to complete the Dutch self-report c.q. other-report version of the SRS. Parents of children with ASD with a confirmed ASD diagnosis themselves were added to the ASD-sample. Only questionnaires without missing items were used for the analyses.

Results: So far,  we have gathered SRS data on about 1000 GP subjects, 180 ASD-P subjects and 21 adults with ASD.
For male respondents there is a statistically significant (p<.0001) difference in SRS total scores between the three groups, on both the self-report (mean scores GP 31.99, ASD-P 36.34, ASD 88.50) and the other-report form (mean scores GP 29.51, ASD-P 41.21, ASD 99.84). In post-hoc pairwise analyses all differences remain significant (p<.0001) except for ASD-P versus GP on the self-report questionnaire (p=.03). By now, we only have data on two female ASD participants. Preliminary results however show a statistically significant (p<.001) difference between GP and ASD-P on the self-report questionnaire in women too.

Conclusions: These preliminary results indicate that (problems in) social responsiveness can be seen as an intermediate phenotype in fathers (and possibly in mothers) of children with an autism spectrum disorder. The results contribute to the hypothesis of genetic variants with each a small effect inherited by the parents as a cause of ASD.