Date of Award


Document Type

Open Access Dissertation




College of Arts and Sciences

First Advisor

Jane E. Roberts


ADHD, ASD, and anxiety are three of the most common co-occurring disorders in children with FXS leading to increased social, academic, and behavioral difficulties (Bailey, Raspa, Olmsted, & Holiday, 2008). Early identification and treatment of these co-occurring mental health disorders is essential to promote optimal outcomes; therefore, the study of early precursors and underlying mechanisms of these disorders within a developmental framework is warranted. The current dissertation includes two sequential and related studies investigating impaired effortful control as a precursor and HPA axis dysfunction (measured through salivary cortisol) as an underlying mechanism to the emergence of ADHD, ASD, and anxiety in young boys with FXS. Results indicate that boys with FXS exhibit lower levels of effortful control and higher levels of cortisol compared to typically developing controls; however, no significant relationship between effortful control and cortisol was found. Additionally, significantly higher levels of ASD symptoms were found in the FXS group. Due to significant variability in individual ADHD, ASD, and anxiety trajectories across FXS and typically developing young boys, no specific trend in developmental trajectories was found. Impaired effortful control did not significantly relate to ADHD, ASD, or anxiety symptoms; however, increased cortisol levels were found to relate to increased anxiety symptoms. Future research is necessary to better understand the development of these disorders within FXS throughout childhood to assist with early detection and treatment efforts.