Date of Completion


Embargo Period


Major Advisor

Deborah Fein, Ph.D.

Associate Advisor

Marianne Barton, Ph.D.

Associate Advisor

James Green, Ph.D.

Field of Study



Doctor of Philosophy

Open Access

Campus Access


Younger siblings of children with autism spectrum disorders (ASD) are at increased risk for ASD and other developmental disorders. Screening children for ASD and other developmental difficulties with tools such as the Modified Checklist for Autism in Toddlers (M-CHAT) has been recommended by the American Academy of Pediatrics as part of toddler well-child visits. Given the increased risk for younger siblings of children with ASD to have developmental difficulties, it is important to investigate how M-CHAT items may characterize the younger sibling population (in this study, younger siblings who do not have an ASD diagnosis). This study considers the similarities and differences in failed M-CHAT and follow-up phone interview items, cognitive skills, adaptive skills, and social development among three groups of children who screened positive on the M-CHAT but who did not have ASD: younger siblings of children with ASD (SIBLING), children screened at their pediatricians’ offices (PED), and children screened at their early intervention offices (EI). The study also characterizes the SIBLING group in terms of social and language skills that may represent symptoms of the Broader Autism Phenotype.

Results indicate that SIBLING children were not more likely to fail any M-CHAT or follow-up interview items than any other group, and they were higher functioning than their EI counterparts. SIBLING received a lower proportion of non-ASD diagnoses and were more likely to be typically developing. These results raise two important issues: that there is a possible contribution of BAP-related symptoms to the manifestation of behaviors that parents perceive as atypical and that result in failing the screener; and that parents of children with ASD are concerned about their subsequent children’s development and may interpret typical or very slightly delayed developmental activities as atypical. SIBLING children may exhibit BAP symptomatology not detected by the M-CHAT, and they may have a diverse range of BAP symptomatology and developmental delays that differs with each child and does not result in failure of specific sets of items. Importantly, results show that failing the M-CHAT and follow-up interview confers significant risk for non-typical development, regardless of the referral group.