Catching up Vs. Falling behind: Longitudinal Investigation of Developmental and Adaptive Skills in Toddlers with ASD

Background:  Previous research has demonstrated deficits in adaptive skills in toddlers with ASD, particularly socialization skills (Ventola et al., 2014). Likewise, high-risk samples have characterized various trajectories of developmental skills in ASD between infancy and toddlerhood, with a recent study identifying stable-average and declining trajectories as those most common (Brian et al., 2014). However, the trajectory of adaptive skills and their relation to overall development in early toddlerhood (i.e., age 3 and earlier) is less clear.

Objectives:  This study seeks to examine longitudinal changes in developmental and adaptive skills among toddlers with ASD.

Methods:  Participants included 24 toddlers (20 males) from a community-referred sample whose families expressed developmental concerns and enrolled in a longitudinal study on social engagement. Two separate visits spanned an average of 15 months (mean age in months at initial visit = 22.89, SD = 4.38), and first-time ASD diagnoses were provided by a multidisciplinary team. Families were offered recommendations regarding interventions that they might choose to pursue (87.5% of families reported subsequent involvement in intervention, with speech therapy, occupational therapy, and special education most commonly endorsed). In addition to the Autism Diagnostic Observation Schedule, Second Edition, toddlers completed a developmental assessment (Mullen Scales of Early Learning) and parents completed an interview on their child’s adaptive behavior (Vineland Adaptive Behavior Scales, Second Edition) at both visits. Analyses compared standardized scores across time points.

Results:  Paired-samples t-tests indicated that Mullen t-scores improved significantly between the two visits on the scales of Receptive Language, t(23) = -3.86, p < .01, and Expressive Language, t(23) = -2.35, p = .03, with a trend in the direction of scores on Visual Reception having improved significantly, t(23) = -1.98, p = .06 (Table 1). However, Fine Motor t-scores became significantly worse between visits, t(23) = 2.47, p = .02. Paired-samples t-tests with Vineland Standard Scores indicated that Communication skills improved significantly between visits, t(23) = -2.72, p = .01, while Daily Living Skills remained statistically unchanged, t(23) = 1.56, p = .13. However, adaptive skills of both Socialization, t(23) = 2.86, p = .01, and Motor Skills, t(23) = 2.90, p = .01, became significantly worse.

Conclusions:  Across most scales/domains of the Mullen and Vineland, community-referred toddlers with ASD evidenced developmental progress between their second year of life and approximately age three, as represented by significantly improved standard scores (Receptive Language, Expressive Language, Communication), or standard scores that remained comparable across time points (Visual Reception, Daily Living Skills). Standard scores in the area of Motor Skills became significantly worse on both measures. Interestingly, despite improved scores in the areas of Receptive and Expressive Language, and also Communication, toddlers evidenced significantly worse Vineland scores in the domain of Socialization. Results highlight the need for interventions that target not only increasing speech/communication, but also improving social interaction, play, and motor skills, which in spite of treatment continue to fall rapidly behind relative to peers. Future research should seek to identify interventions that embed socially-oriented goals into all treatments for young children with ASD.