Developmental Academic Profiles in Siblings of Individuals with ASD

Background: The broad autism phenotype (BAP) refers to a set of subclinical personality and language traits that exist in a subgroup of unaffected relatives of individuals with autism spectrum disorder (ASD) that are qualitatively similar to the defining features of ASD. Studies have begun to disaggregate the neuropsychological and developmental underpinnings of the BAP. In recent work using archival academic testing data, specific childhood academic profiles were reported in individuals who later went on to have a child with ASD, where language skills developed more slowly than reading and math. These profiles predicted both the BAP in adulthood and the severity of their child’s ASD symptoms (Losh et al., 2017), suggesting a potential childhood marker of genetic liability to ASD. Using archival data, this study extended these analyses to siblings of individuals with ASD to investigate whether specific childhood academic profiles may index genetic liability to ASD in clinically unaffected first degree relatives.

Objectives: To examine whether specific childhood developmental academic profiles are evident among siblings of individuals with ASD, constituting a developmental signature reflecting genetic liability.

Methods: Academic test data from the Iowa Test of Basic Skills (ITBS)(Hoover, Dunbar, & Frisbie, 2001) were obtained from siblings of individuals with ASD (n=25) and controls without a personal or family history of ASD (n=32). The ITBS assesses language, reading, and math in grades K-12. Participants also completed an extensive battery of clinical-behavioral and neuropsychological measures.

Results: Differences emerged between groups in language abilities (ps<.04), but not in reading or math (ps>.62). Differences in language were driven by the Language Usage and Capitalization subtests, which assess ability to detect grammatical errors in extended passages and make judgements regarding proper capitalization usage (e.g, distinguishing proper versus common nouns), respectively. Lower performance in language and reading tests were associated with poorer performance on tasks of social cognition later in development (rs>.582, ps<.05) and language fluency (rs>.585, ps< .04), although no associations were found between academic performance and Social Responsiveness Scale or Autism Diagnostic Observation Schedule scores (ps>.22).

Conclusions: Findings suggest a pattern of academic performance in siblings of individuals with ASD that mirrors the profile previously reported in parents, with lower performance in language tests but no differences in reading or math. Also consistent with findings in parents, academic performance was linked to some phenotypic markers associated with ASD suggesting early academic language skills may represent an indicator of later developing social-communication atypicalities related to ASD. Taken together, these findings suggest that academic-related language abilities serve as a potential developmental marker of genetic liability to ASD that might be studied to investigate inter-generational transmission of broader traits associated with ASD.