Social motivation in infancy is associated with familial recurrence of ASD

Abstract

Pre-diagnostic deficits in social motivation are hypothesized to contribute to autism spectrum disorder (ASD), a heritable neurodevelopmental condition. We evaluated psychometric properties of a social motivation index (SMI) using parent-report item-level data from 597 participants in a prospective cohort of infant siblings at high and low familial risk for ASD. We tested whether lower SMI scores at 6, 12, and 24 months were associated with a 24-month ASD diagnosis and whether social motivation's course differed relative to familial ASD liability. The SMI displayed good internal consistency and temporal stability. Children diagnosed with ASD displayed lower mean SMI T-scores at all ages and a decrease in mean T-scores across age. Lower group-level 6-month scores corresponded with higher familial ASD liability. Among high-risk infants, strong decline in SMI T-scores was associated with 10-fold odds of diagnosis. Infant social motivation is quantifiable by parental report, differentiates children with versus without later ASD by age 6 months, and tracks with familial ASD liability, consistent with a diagnostic and susceptibility marker of ASD. Early decrements and decline in social motivation indicate increased likelihood of ASD, highlighting social motivation's importance to risk assessment and clarification of the ontogeny of ASD.

Keywords: autism spectrum disorder; infancy; measurement; social motivation.

Figure 1.

Social Motivation Score Distributions at 6, 12, and 24 Months Social Motivation Index T-score distributions (A-C) among all low- and high-risk participants. Bars (D-F) categorize participants by diagnosis. Gray and black arrows indicate group means for children without and with ASD.

Figure 2.

Social Motivation, Gross Motor Function, and Visual Reception Across Age Trajectories of social motivation (A), gross motor function (B), and visual reception (C) are shown for risk diagnostic groups (LR-, HR-, HR+) based on hierarchical linear models incorporating sex, age (centered at 6 months), ASD familial liability, and interaction of liability with age. In order of increasing familial liability: LR-=low-risk negative, HR-=high-risk negative, HR+=high-risk positive.