Date on Master's Thesis/Doctoral Dissertation

8-2025

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Psychological and Brain Sciences

Degree Program

Clinical Psychology, PhD

Committee Chair

Bufferd, Sarah

Committee Member

Lefler, Elizabeth

Committee Member

Lynn, Andrew

Committee Member

Walter, Bernadette

Author's Keywords

ADHD; peer impairment; comorbidity risk; anxiety

Abstract

Background. Youth with Attention-deficit/hyperactivity disorder (ADHD) often have higher rates of anxiety in comparison to their peers without ADHD. Children with co-occurring ADHD and anxiety exhibit a unique clinical presentation that poses challenges to both assessment and treatment. Consequently, children with comorbid ADHD and anxiety experience increased impairment, and often have poorer long-term outcomes than children with either ADHD or anxiety alone. Preliminary evidence suggests that different psychosocial phenomena commonly experienced by children with ADHD—such as peer functioning—may increase susceptibility to anxiety. Considering that children with ADHD encounter a range of peer difficulties, the present study proposed and evaluated different components of peer functioning in relation to co-occurring ADHD and anxiety symptoms. Method. Across two studies, several common aspects of peer functioning in children with ADHD (i.e., social problems, peer rejection, and low peer support) and underlying ADHD-related mechanisms that contribute to these difficulties (i.e., negative social information processing and rejection sensitivity) were examined both cross-sectionally (Study 1) in a clinical sample of 8-12-year-old children and longitudinally (Study 2) in a community sample of children from age 6 to age 12. In Study 1, parents (N = 120) of children with elevated ADHD symptoms completed questionnaires, and a subset of their children (n = 69, Mage = 9.70, SD = 1.38) completed both questionnaires and a virtual lab task. In Study 2, questionnaire-based data assessments were conducted when children were age 6 years (N = 501, Mage = 6.08, SD = .42; parent-report only), age 9 years (n = 470, Mage = 9.18, SD = .40; parent-, teacher,- and child-report), and age 12 years (n = 476, Mage = 12.66, SD = .46; parent-report only). Primary data analytic procedures included correlations and hierarchical linear regressions to assess associations; moderation and mediation analyses using Process Macro to assess independent moderators and mediators, respectively; and a novel multiple mediation analysis using structural equation modeling (SEM) to examine both the cumulative effects of and interrelations between different mediators. Results. ADHD and anxiety symptoms were consistently significantly related both cross-sectionally and longitudinally from age 6 to ages 9 and 12, and from age 9 to age 12. Further, ADHD and anxiety symptoms were significantly associated with several overlapping components of peer functioning, including social problems (cross-sectionally and longitudinally), peer rejection (cross-sectionally), low peer support (cross-sectionally), and anger rejection sensitivity (cross-sectionally). Social problems at age 9 years partially mediated the relation between ADHD symptoms at age 6 and anxiety symptoms at age 12, accounting for 12.0% of the variance. Social problems, peer rejection, and peer support at age 9 collectively fully mediated the relation between ADHD symptoms at age 6 and anxiety symptoms at age 12. No other components of peer functioning independently mediated or moderated the relation between ADHD and anxiety symptoms, either cross-sectionally or longitudinally. In addition, two significant moderators of the association between ADHD and anxiety symptoms emerged in exploratory analyses. First, the relation between ADHD and anxiety symptoms was stronger among children assigned female at birth compared to children assigned male at birth, both cross-sectionally and from age 9 to age 12. Second, the relation between ADHD and anxiety symptoms was stronger as the number of functional domains (e.g., school, family) in which children were impaired increased. Conclusions. These findings highlight the robust association between ADHD and anxiety symptoms in school-aged children, and further elucidate the role of varying aspects of peer functioning (i.e., overall social problems, peer rejection, peer support, social information processing, and rejection sensitivity) in this relation. While results were not entirely consistent with previous studies, they provide initial evidence that several aspects of peer functioning collectively and independently contribute to the relation between ADHD and anxiety symptoms. Overall, the current study adds to the growing literature emphasizing the influence of psychosocial difficulties on the association between ADHD and anxiety symptoms in children. Although further research is warranted to pinpoint mechanisms of anxiety development in children with ADHD, the present findings suggest that targeting social difficulties in children with ADHD could mitigate anxiety risk.

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