ADHD and Sleep Disorders in Children

Psychiatrists are waking up to the world of sleep and behavior. Just as the biological revolution witnessed a collapse of barriers between the physical and the mental, so the boundary between sleep and wakefulness is crumbling. The emerging discipline of sleep medicine, baptized in the discovery of REM sleep in 1953 and by the characterization of sleep cycles a few years later, initially focused on adult physiology and sleep disorders.

Only in the past 2 decades has the study of children produced a substantial, if sometimes controversial, body of knowledge concerning sleep and its effects on development. Although many findings have been perplexing, the relevance of sleep pathology for behavioral and mental development has been securely established, and some of the most interesting research developments concern the role of sleep in ADHD.

Sleep, cognition, and behavior

Serious sleep problems usually imply either too much or too little sleep. Too little sleep can mean abbreviated sleep episodes, as might be imposed by external demands or by insomnia, or longer episodes punctuated by arousals that fragment sleep. Pilcher and Huffcutt¹ examined the effects of prolonged sleep deprivation (more than 45 hours), brief sleep deprivation (45 hours or less), or partial sleep deprivation (less than 5 hours of sleep in a 24-hour period) on measures of cognitive and motor performance or mood. The overall performance decrement for all measures was 1.37 standard deviations (SDs). This is comparable to a drop in IQ from 100 to about 80. Under the conditions of partial sleep deprivation-not unlike a typical Monday morning for many of us-mood scores dropped by over 4 SDs.

Although children are not suitable subjects for such experiments, Sadeh and colleagues² demonstrated that very modest changes in sleep duration can substantially affect the neurobehavioral function of children. His team monitored 77 fourth and sixth graders in regular classrooms with actigraphy for 5 nights. For the first 2 nights, children slept as usual; on the remaining 3 nights, they were asked to either extend or restrict their sleep time by 1 hour. Children who failed to change their sleep duration by at least 30 minutes were analyzed as “no change.” On a simple reaction time test, performance of both the sleep restriction and no-change groups deteriorated, whereas on measures of digit span and continuous reaction time, children in the extended-sleep group performed significantly better than the others.

When Gruber and associates³ applied a single hour’s sleep restriction to 11 children with ADHD and to 32 controls over 6 days, neurobehavioral function in both groups deteriorated, as assessed by a continuous performance test. For children with ADHD, two-thirds of the continuous performance test measures dropped from the subclinical to the clinical range of impairment.

If the slight manipulations in sleep duration have measurable effects after just 3 nights, what might the effects be when sleep is shortened or fragmented long-term by busy family schedules, sleep-related breathing disorders (SRBD), behavioral insomnia of childhood, or other sleep problems? Would it be possible to produce the full clinical picture of ADHD under such circumstances?

 

 

What is already known about the
correlation between ADHD and sleep disorders in children?

? ADHD has been linked to many types of sleep problems in numerous and methodologically diverse studies. Parent-reported sleep complaints may occur in as many as 50% of children with ADHD.

 

What new information does this article provide?

? This article reviews current thinking on the association between ADHD and sleep disorders that is especially relevant to practicing psychiatrists.

 

What are the implications for psychiatric practice?

? Children presenting with ADHD or ADHD symptoms frequently have sleep problems that parents can describe on a questionnaire or in an interview. Sleep disturbances may aggravate an underlying psychiatric disorder or even fully account for the psychiatric presentation; such information may be critical in diagnosis, referral, and treatment planning.

 

Prevalence of sleep disorders

Sleep problems described in children with ADHD include behavioral problems that often manifest as resistance to bedtime or difficulty in going back to sleep in the middle of the night without caregiver presence, parasomnias, sleep-disordered breathing, restless legs and periodic leg movements, and circadian rhythm disorders.⁴ Similarly, children with ADHD experience alterations in sleep architecture, such as delayed onset of REM, reduced time in REM, and arousals with sleep fragmentation.⁵ Inattention, hyperactivity, neuropsychological deficits, syndromic ADHD, and behavior disorders are also common among children who present with sleep problems. Yet despite abundant evidence of these comorbidities, the extent and nature of possible causal relationships between disturbances in sleep and behavior remain largely a mystery.

Prevalence estimates vary because of the way sleep disorders are operationally defined. Subjective parent complaints about resistance to bedtime, a behavior that is not unusual in children, may be counted as a significant problem or disorder by one investigator but not by another. Laboratories may use different procedures or scoring schemes that produce somewhat inconsistent counts of polysomnographic events, such as leg movements and hypopneas. Similarly, heterogeneous diagnostic rules may yield disparate rates of disorder, ie, if 5 rather than 1 apnea or hypopnea episodes per hour define obstructive sleep apnea, fewer cases with more severe symptoms on average will result. Finally, deviations in sleep architecture detected on polysomnography may be consequential yet may not be indicative of a specific sleep diagnosis. Similarly, diagnoses of ADHD depend on the criteria set, subjective thresholds for counting a behavior as symptomatic, and whether diagnoses are based on rating scales, clinical interviews, or structured and comprehensive clinical assessments.

Rates of sleep disorder in ADHD also depend, sometimes dramatically, on how and where data are obtained. Parent checklists almost always generate high sleep symptom rates, exceeding those that can be demonstrated during formal sleep studies. Research subjects recruited in specialty clinics (such as psychiatry or sleep disorders clinics) often display both sleep and behavior problems, whereas children assessed in regular school settings exhibit fewer problems from either domain.

Further complexity arises from potential nonlinearity in the impact of sleep problems on both behavior and behavioral diagnosis. Thus, mild to moderate levels of sleepiness could produce excessive activity and reduced attention, while very high levels of sleep disturbance may cause torpor and inattention so obviously related to sleep that a separate diagnosis of ADHD would be improvident even if criteria were technically fulfilled.

For all of these reasons, the nature and extent of the relationship between ADHD and sleep remains unsettled. One widely quoted estimate for the prevalence of sleep disorders in ADHD places the rate of parent-reported sleep problems at 25% to 50% in the absence of medication.⁶ Spruyt and Gozal,⁷citing this study, give a guess-estimated rate of sleep problems in children with ADHD as 5-fold greater than that in healthy controls.

High-end estimates of sleep disorder prevalence in ADHD populations include a report from an Italian clinic that yielded polysomnography-confirmed sleep disorders, such as periodic limb movements in 40%, restless legs syndrome in 26%, SRBD in 18%, and confusional arousals in 36%.⁸ Findings from one study showed that 73% of children with ADHD had sleep problems and 45% of those had moderate to severe problems.⁹

Inconsistencies among reports have clouded interpretation of findings relative to sleep morbidity and ADHD. A recent meta-analysis produced compelling findings for both subjective and objective sleep measures in children with ADHD. In their analysis, Cortese and associates¹⁰ minimized the likelihood that comorbid conditions could account for sleep problems by excluding studies in which children were receiving pharmacological treatment or had comorbid depressive or anxiety disorders. Compared with controls, children with ADHD had significantly higher bedtime resistance and more sleep onset difficulties, night awakenings, morning wakening difficulty, sleep-disordered breathing, and daytime sleepiness. Among objective measures, sleep onset latency, stage shift frequency, and apnea-hypopnea index were increased in children with ADHD, while sleep efficiency, true sleep time, and average time to fall asleep were lower than in controls.

Notwithstanding our inability to identify true prevalence rates, studies purporting to show frequent sleep disorders are probably a fair reflection of the rate at which clinicians who see children with ADHD can expect to hear complaints of sleep problems after a careful inquiry using some combination of rating scale or checklist and interview. Children referred for diagnosis and treatment of sleep disorders or for adenotonsillectomy are likely to display psychiatric problems in which inattention, hyperactivity, or both are prominent.

Restless legs syndrome and periodic limb movements

In their meta-analyses, Sadeh and colleagues¹¹ found that the frequency of periodic limb movements was consistently elevated in children with ADHD. The comorbidity of restless legs syndrome symptoms in ADHD has been reported to be as high as 24%.^12,13 Frequent parent reports of prominent periodic limb movements, restless legs syndrome, and growing pains in their children with ADHD offer a plausible mechanistic link between sleep movement disorders and ADHD, namely, a functional dopamine deficit.¹² Both restless legs syndrome and periodic limb movement disorder can be successfully treated with dopamine agonists, much as ADHD usually responds to stimulant medication.

The diagnosis of restless legs syndrome is based on history and requires that the child offer some description of subjective symptoms. Children describe the discomfort that compels movement in restless legs syndrome in idiosyncratic ways; patience and creativity may be needed to understand such communications.

Most patients who experience restless legs syndrome also have periodic limb movements, although the converse is not necessarily true. In contrast to the voluntary movements of restless legs syndrome, periodic limb movements are involuntary and have a distinctively “neurological” appearance. The movements last from 0.5 to 5 seconds and recur in cycles of 5 to 90 seconds, typically in clusters, during non-REM sleep.

Both restless legs syndrome and periodic limb movement disorder can reduce the amount or quality of sleep. Restless legs syndrome prevents sleep onset and the return to sleep after awakenings at night, whereas periodic limb movement disorder may cause arousal and sleep fragmentation. Occasional limb movements are not necessarily problematic. Treatment recommendations for periodic limb movement disorder and restless legs syndrome are sleep hygiene, iron supplementation, and medications.

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