The impact of comorbid mental health symptoms and sex on sleep functioning in children with ADHD.

Children with attention-deficit/hyperactivity disorder (ADHD) display more sleep problems than their peers, but it remains unclear whether comorbid mental health symptoms [i.e., anxiety, depression, oppositional-defiant disorder (ODD)] are uniquely related to sleep functioning. It is also largely unknown whether boys and girls with ADHD differ in their sleep functioning. This study (1) examined whether boys or girls with ADHD differ in their sleep functioning, (2) evaluated comorbid symptoms as uniquely related to sleep functioning domains, and (3) explored whether sex moderated associations between comorbid symptoms and sleep. Participants were 181 children (ages 7-13; 69% male; 82% White) diagnosed with ADHD. Parents completed measures assessing their child's ADHD symptoms, comorbid symptoms, and sleep functioning. Girls had poorer sleep functioning than boys across most sleep functioning domains. Sixty percent of children met cutoff criteria for having sleep problems, though rates differed significantly between girls (75%) and boys (53%). No differences in rates of sleep problems were found between ADHD subtypes/presentations or between younger and older children. In path models including ADHD and comorbid symptom dimensions, anxiety symptoms were uniquely associated with increased bedtime resistance and sleep anxiety, ADHD hyperactive-impulsive symptoms were associated with more night wakings and more parasomnia behaviors, and ODD and depressive symptoms were associated with shorter sleep duration. Depression was also uniquely associated with increased daytime sleepiness and overall sleep problems. Sex did not moderate associations between comorbid symptoms and sleep problems. This study provides important preliminary evidence that girls with ADHD experience more sleep problems than boys with ADHD. Findings also demonstrate that the associations between comorbid symptoms and sleep functioning in children with ADHD vary based on both the specific symptoms and sleep domains examined.