A study in the March 1 issue of the journal SLEEP suggests the presence of an intrinsic sleep problem specific to attention-deficit/hyperactivity disorder (ADHD) and supports the idea that children with ADHD may be chronically sleep deprived and have abnormal REM sleep.

Results show that children with ADHD have a total sleep time that is significantly shorter than that of controls. Children in the ADHD group had an average total sleep time of eight hours, 19 minutes; this was 33 minutes less than the average sleep time of eight hours, 52 minutes, in controls. Children with ADHD also had an average rapid eye movement (REM) sleep time that was significantly reduced by 16 minutes.

According to the principal investigator and the lead author, Reut Gruber, PhD, director of the Attention, Behaviour and Sleep Lab at the Douglas Mental Health University Institute, results of the study were encouraging, as the researchers were able to control for many confounding factors, which reduced some of the confusion and contradictions discovered in previous studies. Measuring sleep architecture in the children's beds at home using portable PSG, also allowed researchers to better represent the natural sleep pattern, thus increasing the validity of the study.

"I do not believe that sleep per se is the cause of ADHD, but it may make the symptoms worse in children with sleep problems. There are reports in the literature in which treating sleep problems led to improvement in ADHD symptoms but I suspect that these results were seen in children with sleep apnea. More research needs to be done in order to determine if sleep affects ADHD children with no primary sleep disorder."

According to the authors, ADHD is one of the most prevalent conditions in child psychiatry, and 25 percent to 50 percent of children and adolescents diagnosed with the disorder have clinically reported sleep problems. Partial sleep loss on a chronic basis accumulates to become a sleep debt, which can produce significant daytime sleepiness and neurobehavioral impairment. Studies also have shown that disrupted sleep can affect daytime learning and attention in childhood and can lead to ADHD-like symptoms.

Portable polysomnography sleep recorders were used to perform overnight sleep recordings on 15 children diagnosed with ADHD without comorbid psychiatric problems, and on 23 healthy controls. The children were between the ages of 7 and 11, were not taking medication and were instructed to avoid products containing caffeine for at least seven days leading up to the overnight sleep study, which was performed in each child's home.

Parents completed the Child Behavioral Checklist, a 113-item questionnaire assessing behavioral and emotional problems. Children also were assessed for pubertal development. Factors such as age, sex, gender, socioeconomic status and parents' marital status were controlled.

According to the authors, this study may suggest that ADHD children suffer from an intrinsic sleep problem that could be related to the underlying pathophysiology of the disorder. They report that the impact of sleep duration on neuropsychological functioning in children with ADHD should be investigated further. Additional studies also will be required to examine whether shorter sleep duration in children with ADHD is associated with ADHD-like symptoms, including behavioral problems and poor neurocognitive functioning. The authors suggest that if a functional alteration of sleep in children with ADHD can be confirmed, then it may be possible to develop therapeutic approaches for optimizing and individualizing the children's sleep regimes.