Sleep duration and intensity of ADHD symptoms.

Attention deficit/hyperactivity disorder (ADHD) is one of the most common childhood psychiatric disorders. Its symptoms involve patterns of inattention, hyperactivity, and impulsivity, which are associated with global, social, academic, and adaptive impairment; need for treatment increases with each additional symptom. Children with ADHD commonly experience sleep problems, which add to difficulties in their daily life. Even in children with typical development, sleep deprivation can lead to behaviors similar to symptoms of ADHD, such as hyperactivity as a behavioral way of stabilizing vigilance (‘‘brain arousal’’), and cognitive deficits that can induce inattention. Although sleep duration appears not to be significantly different between children with typical development and those with ADHD, sleep duration might be associated with the intensity of ADHD behaviors, even in children with the disorder. In this study, approved by the Ethics Committee of Universidade Federal de Minas Gerais, Brazil, 142 children with ADHD (116 boys and 26 girls; 42 inattentive, 10 hyperactive/impulsive, and 90 combined), aged 6 to 15 years (mean age = 9.42 years, standard deviation [SD] = 2.25) were enrolled. Caregivers completed the Brazilian version of the Schedule for Affective Disorders and Schizophrenia for School-Aged Children-Present and Lifetime Version (K-SADS-PL), and current inattentive (median = 8, mean = 7.39, SD = 1.73) and hyperactive-impulsive (median = 7, mean = 6.30, SD = 2.86) symptoms were recorded. The sum of inattentive and hyperactive-impulsive symptoms can range from 0 to 9 for each dimension. Participants’ sleep duration (time asleep at night, in hours) was computed as perceived by the caregiver (median = 10, mean = 9.34, SD = 1.40), who reported the child’s current time of sleep onset and current time of waking. Spearman’s correlation showed a significant negative association between sleep duration and inattentive symptoms (r(141) = -0.185, p = 0.027), but not with hyperactive-impulsive symptoms (r(141) = 0.101, p = 0.230). Participants with ADHD were then split by median inattentive symptoms, and the low-inattentive group (n=71, median = 7 symptoms) was shown to sleep more hours (median = 10 hours, mean = 9.58, SD = 1.42) than the high-inattentive group (n=71, median = 9 symptoms; median = 9 hours, mean = 9.10, SD = 1.34) (U = 1.982, p = 0.024, r = -0.189). Considering the complex origin of ADHD symptomatology and the knowledge that functional impairments are related to symptom intensity, even a small association should not be ignored. Inattentive symptoms seem to play a crucial and unique role in academic performance for children with ADHD, for example; thus, adequate investigation of sleep habits and ADHD symptomatology could be important not only to reduce ADHD severity but also to improve outcomes. Although we did not investigate the rate of sleep problems in our sample, sleep problems have been shown to be frequent and relevant to the management of children with ADHD. ADHD and sleep problems may share neurobiological pathways (cortical areas associated with regulation and arousal). However, these problems are thought to add functional impairments other than those caused by ADHD alone. This study has limitations that should be taken into account, such as the absence of medication control, lack of characterization of comorbid psychiatric disorders such as internalizing problems associated with insomnia, and lack of objective measures to determine sleep duration. Of note, although subjective and objective measures of sleep duration are moderately correlated, subjective measures (as used in this study) are usually biased. At any rate, our results suggest that sleep measures that are not commonly observed to differ between children with ADHD and children with typical development might still be useful for characterizing the role of sleep issues in ADHD severity. Most importantly, behavioral sleep interventions have demonstrated substantial and sustained benefits for improving sleep duration in children with ADHD, which highlights the potential benefit of sleep characterization in this population.