Developmental Profiles of Infants and Toddlers with Autism Spectrum Disorders Prospectively Identified In a Community-Based Setting

Background:  To date, no study has focused on the cognitive profiles of young children identified prospectively in a community-based sample. The findings from high-risk sibling studies and studies using clinic-referred children may not be applicable to those children identified via developmental surveillance or primary level screening. It is therefore important to ascertain whether the findings from these studies are generalizable to children identified from community-based samples.

Objectives:  The objective in the current longitudinal study was to investigate the developmental profiles of children with Autism Spectrum Disorders (ASD) from 12- to 24-months, who had been prospectively identified through developmental surveillance in a community-based sample.

Methods:  A total of 110 children with Autistic Disorder (AD), ‘broader’ ASD, and developmental and/or language delays (DD/LD) were assessed using the Mullen Scales of Early Learning (MSEL; Mullen, 1995) at 12-, 18-, and 24-months of age. These children were drawn from a larger sample of 20, 770 children, monitored as part of the Social Attention and Communication Study (SACS).

Results:  Children with both AD and 'broader' ASD performed below age-appropriate norms on the MSEL, with the exception of Fine Motor skills at 12- and 18-months of age, which was an area of strength. Furthermore, those in the AD group performed more poorly, overall, than the ASD and DD/LD groups on the MSEL.  The children with autism (AD and ASD) were seen to display an uneven cognitive profile, with poorer performance on verbal skills (particularly Receptive Language) relative to nonverbal skills. The children with broader ASD displayed a similar developmental profile to children with DD/LD, with their profiles only differing in their Receptive Language abilities at 24-months of age. In addition, overall performance on the MSEL was seen to decline across time in the children with AD and ASD due to developmental stagnation.

Conclusions:  This is the first prospective, longitudinal study of the developmental profiles of children with autism from a community-based sample. The study's findings suggest that a severe deficit in Receptive Language may be the core cognitive impairment that determines whether a child will develop autism or continue to show developmental or language problems without autism. The findings also highlight the urgency of identifying children with autism and intervening as early as possible. Timely intervention may affect crucial changes during the critical period of development between 12- to 24-months, where developmental stagnation is all but too apparent in young children with autism.