Negative Affect Longitudinally Predicts Anxiety, not Autism, in Young Children with Fragile X Syndrome

Bridgette L. Tonnsen, University of South Carolina


Children with fragile X syndrome (FXS) face extremely high risk for anxiety disorders, yet few studies have longitudinally investigated FXS as a high risk sample for teasing apart the early manifestations of debilitating anxiety symptoms. Due to the high comorbidity and overlapping phenotypic features of autism and anxiety within FXS, investigating precursors of anxiety in FXS requires consideration of autistic symptoms. The present study sought to characterize the relationship between early longitudinal trajectories of negative affect (measured between ages 8-71 months) and both anxiety and autistic outcomes (mean age = 58 months, SD =10.7) in a young sample of males with FXS (n=25). Multilevel modeling revealed significant relationships between anxiety outcomes and mean levels of fear, soothability, and sadness; as well as increasing approach over time. Contrary to our hypotheses, autism outcomes were not related to mean levels or change in temperament. These findings suggest that within FXS, early negative affect may serve as a salient indicator of anxiety outcomes independent of autism status. Future research is warranted to determine the specificity of negative affect to anxiety in FXS, as well as to explore potential moderators affecting this relationship. Studying the relationship between early temperament trajectories and anxiety disorders within FXS may lend insight into longitudinal precursors of anxiety disorders, as well as inform etiology and treatment considerations specific to young children with FXS.