Objectives: To identify behavioral markers at 6 months predictive of ASD at age 3 years, using longitudinal data from a high-risk cohort of younger siblings of children with ASD.
Methods: Participants included 231 high-risk infants (HR; younger siblings of children with ASD) and 145 low-risk comparison infants (LR) followed from age 6 months to 3 years. Early markers of ASD were assessed using the Autism Observation Scale for Infants (AOSI; for details see Bryson et al, 2008) at 6 months. Clinical best estimate ASD diagnoses were determined using the ADI-R, ADOS and DSM-IV-TR blind to prior assessments. AOSI item scores were compared in HR infants diagnosed with ASD at 3 years (HR-ASD), HR infants not diagnosed with ASD (HR-N) and LR infants, with further pair-wise comparisons among these groups. To take into account multiple comparisons (as well as intercorrelations among AOSI items), critical p-value for significance was set at p<.01.
Results: Of 231 high-risk infants, 51 were diagnosed with ASD at 3 years (22.1%). HR infants (both HR-ASD and HR-N) differed from LR infants with respect to reduced or atypical anticipatory social responses, eye contact, and social referencing. Only reduced/atypical motor control was ASD-specific at 6 months; that is, more common in HR risk infants who developed ASD compared to both HR-N and LR infants. In addition, HR-ASD differed from LR infants on reactivity and engagement of attention (see Table for details).
Conclusions: Based on behaviors observed on the AOSI, HR infants (regardless of ASD outcome) differed from LR infants at 6 months in respect to reduced/atypical anticipatory social responses, eye contact, and social referencing. Only reduced/atypical motor control distinguished ASD within the HR group at 6 months; i.e., was more common in HR infants who developed ASD compared to both non-diagnosed HR infants, as well as LR infants. In addition, HR infants with ASD differed from LR infants at 6 months on observed reactivity and engagement of attention, consistent with parent-reported temperamental profiles (Garon et al., 2008; in preparation). These findings will be discussed in the context of the evolving behavioral profile observed at subsequent time points, and in relation to current hypotheses regarding the role of attention and affect regulation in the early expression of ASD vulnerability.
See more of: Clinical Phenotype
See more of: Symptoms, Diagnosis & Phenotype