AUTISM SPECTRUM DISORDERS IN FRAGILE X: DIFFERENTIAL CONTRIBUTIONS OF ADAPTIVE SOCIALIZATION AND SOCIAL WITHDRAWAL

Objectives: Extending our previous work on the profile of social behaviour abnormalities in Fragile X (FraX) boys, we examined the relative contribution of social withdrawal and delayed adaptive socialization to the diagnosis of autism spectrum disorder (ASD).

Methods: We analyzed item components of instruments rating adaptive (e.g., Vineland Scales) and problem (e.g., Aberrant Behavior Checklist) behaviors in two cognitively-characterized (i.e., IQ, language) cohorts of FraX boys (3–8 years), a larger main cohort for cross-sectional analyses (n=56, 24 with ASD) and a longitudinal subset (n=30, 11 with ASD) of the main cohort with up to three yearly observations. We used a combination of multivariate and logistic regression analyses, including age and IQ as co-variates.

Results: We found that: (1) as delayed socialization, social withdrawal is also a correlate of ASD in FraX; (2) items of social withdrawal scales representing social avoidance were the main predictors of ASD status, particularly in older boys; (3) adaptive socialization skills reflecting rules of social behavior and recognition and labeling of emotions, which were linked to verbal reasoning abilities, were selectively associated with ASD in FraX; (4) among social behaviour parameters, adaptive socialization is the primary determinant over time of ASD status in FraX boys; and (5) integrated social withdrawal-adaptive socialization models allow the identification of distinctive FraX+ASD subgroups.

Conclusion: Our findings suggest that two discrete but interrelated social behavior abnormalities, one linked to impaired cognitive processes and the second one to exaggerated emotional responses, play a role in the development of ASD in FraX boys.