Growth Trajectories in Initiating Joint Attention during the First Three Years of Life in Siblings of Children with Autism Spectrum Disorder

Background:  Since initiating joint attention (IJA) is impaired in children with autism spectrum disorder (ASD), many researchers are currently studying the development of IJA and its relations to outcome in children who have an older sibling with ASD. This could lead to insight into differential pathways in the early development of these children: younger siblings who also have ASD themselves, siblings on the broader autism phenotype, and non-affected siblings.

Objectives: To explore differences in growth trajectories in IJA: a) between siblings of children with ASD compared to typically developing children and b) within the group of siblings according to their autism symptomatology at 36 months and their diagnostic outcome.

Methods: The Early Social Communication Scales (ESCS) were administered to siblings of children with ASD (SIBS; n = 36) and to typically developing children (TD; n = 32) at 9, 12, 18, 24, and 36 months of age. Rates per minute were calculated for IJA bids. The proportion of higher level IJA bids (i.e., pointing or showing) to the total number of IJA bids was used as a measure of the quality of nonverbal IJA bids. In addition, the Dutch version of the MacArthur-Bates Communication Development Inventories (N-CDI’s) was administered at the ages of 18 and 24 months to assess the acquisition of spoken words. Finally, the Autism Diagnostic Observation Schedule (ADOS) was administered at 36 months as a measure of ASD symptomatology by means of the ASD severity scores (see Gotham, Pickles, & Lord, 2009). Currently, all children are being contacted to collect information about community clinical diagnosis. The Autism Diagnostic Interview-Revised (ADI-R) will be administered to children with a community clinical diagnosis and to children who scored above the ASD cut-off on the ADOS at 36 months. A clinical best estimate diagnosis will be given by a team of licensed clinical psychologists. 

Results:  At the conference, results of hierarchical linear modeling (HLM) will be presented to examine initial status of IJA at 9 months and growth in IJA between 9 and 36 months in relation to language acquisition between 18 and 24 months, autism symptom severity at 36 months, and diagnostic outcome. Since data collection on diagnostic outcome is still ongoing, only preliminary results comparing TD children and SIBS are summarized here. A decline was noted in the total frequency of IJA for TD children between 12 and 18 months, whereas in SIBS this was observed between 18 and 24 months. SIBS show an increase in the proportion of higher level IJA bids until 18 months, whereas TD show a growth until 24 months (see Figures). Also, the total frequency of IJA at 18 months was related to autism symptom severity at 36 months in both groups.

Conclusions:  Differences in IJA trajectories between SIBS and TD children were most apparent between 18 and 24 months. Further analysis with HLM and complete outcome data will be presented and considered in the light of possible relations between these IJA trajectories, concurrent language acquisition, and autism symptom severity at a later age.