Objectives: To examine the emergence of and relationship between social communication and repetitive movements in children with ASD identified prospectively between 12 and 36 months. To determine if early symptom domains predict cognitive level and autism symptoms at 3 years.
Methods: Participants were recruited from two sources: 1) general pediatric sample screened by the FIRST WORDS Project (low-risk) and 2) children referred for suspected ASD or status as an infant sibling (high-risk). CSBS Behavior Samples were administered periodically between 12 and 36 months and coded for social communication (n=599) and repetitive movements (n=242). Measures of social communication on the CSBS included Social, Speech and Symbolic composites and measures of repetitive movements included Body and Objects composites. Autism symptoms were measured at age 3 with the Autism Diagnostic Observation Schedule (ADOS) and cognitive level with the Mullen Scales of Early Learning. A best estimate diagnosis of ASD (n=229) or developmental delay where ASD was ruled out (DD; n=91) was made for 320 children.
Results: The ASD group showed very slow rates of change on the CSBS Social composite over the second and third year, in contrast to the DD group which showed significant growth. Within the Social composite, the ASD group showed no change in Social Referencing, slow improvement in Communication, and significant improvement in Gestures. In contrast, both diagnostic groups showed significant growth in Speech and Symbolic. Further, both groups showed early emergence of and stability in Repetitive Movements with Body and Objects across the second and third years. Social communication was not significantly related to repetitive movements with objects early in the second year, however, moderate correlations were observed later. This finding was not observed in Repetitive Movements with Body. Social communication early in the second year significantly predicted nonverbal and verbal cognitive level at age 3 (R=.53, p<.001) and this predictive relationship strengthened late in the second year (R= .69, p<.001). Repetitive movements throughout the second year did not significantly predict cognitive level. Social communication in the second year significantly predicted ADOS total algorithm scores with more variance explained later in the second year(R=.36, p=.004 early; R=.57, p<.001 late) and Repetitive Movements with Objects added significantly to this model (R=.45, p=.014 early; R=.68, p<.001 late).
Conclusions: These results suggest a deceleration of growth of some social skills in the second year compared to significant growth in speech and symbolic skills in children with ASD. Social communication and repetitive movements predicted autism symptoms by early in the second year but only social communication predicted cognitive level, and these relationships strengthen as the symptoms unfold over the second year. The significant role of repetitive movements in this unfolding appears to be limited to movements with objects.