Childhood Disintegrative Disorder (CDD) is a rare and poorly understood Autism Spectrum Disorder (ASD) characterized by a dramatic regression of adaptive skills after > two years of normal development. Previous studies have found that, subsequent to regression, children with CDD have worse outcomes than their counterparts with Autistic Disorder (AD) in terms of the number of functional domains impacted and the degree to which each domain is impacted. However it is unclear whether these differences are sustained over time. It has also been established that children with CDD have, on average, greater intellectual disability than those with AD. However, to date, children with CDD have not been compared to an IQ matched group with AD. Thus it is unclear whether intellectual function mediates the differences in adaptive outcome, or whether some more fundamental difference in the neuropathology of the disorders is responsible.
Objectives:
To compare adaptive behavior capacities and adaptive trajectories of children with CDD to a cognitively similar group with AD. To examine the adaptive behavior profiles associated with CDD to determine whether the disorder has differential impact on specific domains.
Methods:
In comparison 1, the domain and subdomain scores on the Vineland Adaptive Behavioral Scales of 11 children with CDD were compared to the scores of an age, IQ and gender matched group with AD usinga two-tailed paired t-test of dependent means. Effect sizes were calculated by dividing the average difference between groups divided by the standard deviation of the difference between groups, and were ranked according to standards developed by Cohen. In comparison 2, the trajectory of progress for each CDD subject was calculated for the Vineland domains and subdomains in units of change in age-equivalent score per chronological year. A t-test of dependent means was used to compare the rates of change between categories. Due to the impossibility of matching subjects on the basis of age, IQ, gender, as well as the interval between testing periods, in comparison 3, the average progress of the CDD group in each domain and subdomain was compared to the rate of change of a line fit to the single time point scores of age, IQ and gender matched subjects with AD. All results were adjusted using the Bonferroni method.
Results:
In comparison 1, the differences in composite adaptive behavior, communication scores and receptive language sub-scores reached significance at p<0.05, however were not significant once adjusted. In comparison 2, rates of expressive language change were higher than other subdomain scores, however a comparison between rates of change in general Vineland categories did not reach significance. In comparison 3, adaptive trajectories did not distinguish the CDD subjects from the AD group.
Conclusions:
CDD and AD can be distinguished by pattern of onset and level of cognitive impairment. However once IQ is factored in, children with CDD have similar adaptive levels and trajectories to their counterparts with AD. Furthermore, children with CDD demonstrate no significant differences in the degree to which individual adaptive domains are impacted, experiencing a generalized skill loss.