Response: 'Acute Impact of Immediate Release Methylphenidate Administered Three Times a Day on Sleep in Children with Attention-Deficit/Hyperactivity Disorder'

We appreciate the opportunity to respond to the issues raised in the commentary regarding our recent publication in the Journal of Pediatric Psychology entitled ‘‘Acute Impact of Immediate Release Methylphenidate Administered Three Times a Day on Sleep in Children with AttentionDeficit/Hyperactivity Disorder.’’ A number of interesting points were made by the author of the commentary, some of which we are able to directly address and others which we addressed only in a speculative manner. Although research in the field of pediatric sleep is growing, there are still many questions that remain unanswered, particularly regarding the link between sleep and childhood psychopathology. As the author of the commentary correctly points out, there is limited research examining the daytime consequences of sleep deprivation in children. However, it is important to highlight that the daytime sequelae of sleep deprivation in adults have been well documented in the literature. For adults, sleep deprivation has been shown to have significant consequences for mood, cognition and motor performance (for a review see Pilcher & Huffcutt, 1996). Executive attention, working memory, and divergent thinking involved in decision making are some of the specific cognitive abilities found to be most vulnerable to sleep deprivation (Durmer & Dinges, 2005). An excellent review (Sadeh, 2007), published after submission of our manuscript, evaluates the research to date regarding the impact of sleep deprivation on children’s daytime functioning. Sadeh reviews the fairly large body of correlational research as well as the few experimental studies conducted which examine children’s response to sleep deprivation/sleep loss. Correlational research has demonstrated that poor sleep in children is associated with deficits in working memory, executive functioning, and attention, as well as poorer academic achievement, more behavioral problems, difficult temperament, increased negative mood, and poor emotional regulation. However, causal relationships cannot be inferred given the nature of this research. Sadeh notes that the results of the few published experimental studies, although not entirely consistent, have generally found that complex tasks (e.g., executive functioning, attention) are sensitive to sleep deprivation/restriction. The findings in children are similar to those found in the literature on adults. Based on this review, Sadeh concludes that: (a) there is converging evidence that sleep loss/poor sleep directly results in daytime sleepiness in children and (b) there is reasonable empirical support that sleepiness results in poorer neurobehavioral functioning (evidence is strongest for deficits in the areas of attention regulation, working memory, and executive functioning). There is a growing body of research examining the relationship between attention-deficit/hyperactivity disorder (ADHD) and sleep problems. Some researchers hypothesize that ADHD can be the direct result of sleep deprivation (e.g., due to sleep apnea); whereas, other researchers suggest that ADHD symptoms may be exacerbated by coexisting sleep problems. We are not aware of any research that hypothesizes that ADHD symptoms are the result of too much sleep, as suggested by the author of the commentary. In fact, many studies utilizing parent report have found that children with ADHD sleep less than typically developing (TD) children. However, there are exceptions to this finding (both when sleep duration is measured subjectively and objectively). One such exception was from our previous study (Corkum, Tannock, Moldofsky, Hogg-Johnson, & Humphries, 2001), in which we compared sleep in medication naı̈ve children with ADHD to children who were TD. We measured sleep using multiple measures, including a parent questionnaire, sleep diary, and actigraphy. A similar pattern was found across measures in that the ADHD group slept longer (17–23 min longer depending on the measure