Date of Completion


Embargo Period


Major Advisor

Deborah Fein, Ph.D.

Associate Advisor

Marianne Barton, Ph.D.

Associate Advisor

Diana Robins, Ph.D.

Field of Study



Doctor of Philosophy

Open Access

Open Access


Most Autism Spectrum Disorder (ASD) screening measures have been developed for level 1 screening in low-risk (LR) children. Measures may perform differently in high-risk (HR) populations, such as younger siblings of children with ASD, due to parent factors (i.e., experience with ASD) and child factors (i.e., increased prevalence of ASD symptoms). The current study sought to investigate the performance of an ASD screening measure, the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F), in a sample of HR younger siblings (n = 187) and directly compare its performance to that in a LR comparison sample (n = 15,848). The M-CHAT-R/F demonstrated a significantly higher screen positive rate and ASD detection rate in the HR sample compared to the LR sample. High predictive power of the M-CHAT-R at initial screen, with limited incremental change after Follow-Up, suggests that the Follow-Up is less critical in a HR sample. A significantly reduced rate of changed responses during Follow-Up further supports improved reporting accuracy of parents with ASD experience. Response to name was the best discriminating item regardless of risk group, although other discriminating items differed. HR-ASD toddlers had higher cognitive functioning compared to LR-ASD toddlers in the face of comparable ASD severity. This pattern of results is indicative of differential parent responding as opposed to behavioral differences between risk groups. In sum, the findings of the current study suggest that the M-CHAT-R/F can accurately distinguish between ASD and Non-ASD within the first two years of life in a HR sibling sample.