Review ArticleSleep and ADHD
Introduction
Attention-deficit/hyperactivity disorder (ADHD) is one of the most common childhood behavioral disorders, with an estimated worldwide prevalence of approximately 5% in school-age children [1]. According to the diagnostic and statistical manual of mental disorders, fourth edition-text revised (DSM-IV-TR), ADHD is characterized by developmentally inappropriate symptoms of inattention, hyperactivity, and/or impulsivity, with onset before the age of 7 years, and impaired functioning in two or more settings (e.g., at school and at home [2]).
Complaints of sleep problems in children with ADHD are not uncommon in clinical practice. According to Corkum et al. [3], they are reported in up to 55% of cases. The first descriptions of sleep disturbances associated with ADHD were reported in the 1950s by Laufer and Denhoff [4], who noted, “Generally, the parents of hyperkinetic children are so desperate over the night problems that the daytime ones pale in significance.” Afterwards, in 1973, Wender [5] reported that children with “minimal brain dysfunction” (an old nosographic category including children with behavioral features similar to those found in ADHD) had “an increased frequency of sleep difficulties: difficulty in falling asleep and remaining asleep, and early awakening.” However, after these initial observations, the relationship between ADHD and sleep disturbances has been regrettably overlooked by researchers and clinicians in the field. Fortunately, in the last 10–15 years, a renewed interest has been devoted to the relationship between ADHD and sleep disorders. Using subjective (i.e., based on questionnaires) and objective (i.e., neurophysiological) measures, several groups have attempted to clarify the links between ADHD and sleep disorders.
Research in this topic is relevant from a theoretical standpoint, suggesting possible novel etiopathophysiological models of ADHD as well as new insights into the effects of sleep alterations on behavioral and cognitive functions. Advances in this field may also have a tremendous impact on day-to-day clinical practice. On one hand, the management of sleep problems in children with ADHD may significantly reduce behavioral symptom severity and improve the quality of life of these children as well as that of their families [6]. On the other hand, taking into account sleep disturbances may also be paramount in the assessment and treatment of children who are sent for consultation for symptoms of inattention, hyperactivity, and/or impulsivity but do not meet DSM-IV diagnostic criteria for ADHD. Indeed, it has been pointed out that any sleep disorder that results in inadequate sleep duration, fragmented or disrupted sleep, or excessive daytime sleepiness can lead to or contribute to problems with mood, attention, and behavior [6]. As a consequence, at least in a subsample of patients referred for inattention, hyperactivity, and/or impulsivity, these symptoms may be improved or even eliminated upon treatment of the primary sleep disorder.
In this paper we focus on the most common sleep alterations found in children with ADHD. To discern information pertinent in day-to-day clinical practice with ADHD children, we present a critical updated overview of the most relevant studies on the prevalence, etiopathophysiology and treatment strategies of sleep problems in ADHD and discuss some possible future avenues of research in the field.
Section snippets
Sleep and ADHD: general considerations
Although clinicians, particularly child psychiatrists, might believe that sleep alterations in children with ADHD are due exclusively to the effects of ADHD drugs (particularly stimulants), available evidence suggests that ADHD drugs are only one of the possible causes of sleep disturbances associated with ADHD and that children with ADHD do present with significantly more sleep disturbances than controls, independently from medication use. As for the nature of these problems, in previous
Restless legs syndrome (RLS)
The first descriptions pointing to a possible association between RLS and ADHD were provided by Picchietti and Walters [10]. In a review of the literature [11] conducted in 2005, we concluded that up to 44% of subjects with ADHD have been found to have RLS or RLS symptoms, and up to 26% of subjects with RLS have been found to have ADHD or ADHD symptoms. However, these data should be considered with caution given some methodological limitations of the reviewed studies (concerning the methods
Periodic limb movements in sleep (PLMS)
In a series of studies, Picchietti et al. suggested an increased prevalence not only of RLS, but also of periodic limb movements in sleep (PLMS) among children with ADHD [29], [30]. Moreover, Huang et al. found that 10.2% of children with ADHD had periodic limb movement disorder (PLMD) compared to 0% of controls [31]. This association has also been examined and confirmed by Bruni et al. [32], who pointed out that limb movements (LMs) in ADHD have low levels of periodicity, suggesting that the
Sleep-onset insomnia and dim light melatonin onset delay
It has been reported that medication-free children with ADHD and sleep-onset insomnia (SOI) exhibit a delayed evening increase in endogenous melatonin levels [34]. Therefore, it has been hypothesized that SOI in ADHD is a circadian rhythm disorder due to a dim light melatonin onset delay [34]. This may underlie and contribute to symptoms of bedtime discomfort with secondary resistance to go to bed, which may be erroneously considered as the expression of a general “oppositional-defiant
Increased nocturnal motor activity
Studies utilizing actigraphy have documented an excessive nocturnal motor activity (in the arms or in the legs) in children with ADHD [42], [43]. Only one study [44], conducted by our group, analyzed excessive nocturnal activity in children with ADHD by means of infrared camera, confirming that children with ADHD moved significantly more often than controls and that the duration of movements was significantly longer in ADHD children. Although one might suppose that increased nocturnal motor
Sleep-disordered breathing and ADHD
The relationship between sleep-disordered breathing (SDB) and ADHD (as categorical diagnosis according to DSM criteria) is still controversial [51]. The results of several studies have demonstrated an association between symptoms of SDB and ADHD [52], [53]. However, as some of these investigations did not use DSM-IV ADHD criteria, it is not clear whether SDB is linked with ADHD symptoms or with ADHD as a disorder diagnosed according to the standardized criteria. The above mentioned
Deficit in alertness
Children with ADHD may have a deficit in alertness. It has been hypothesized that excessive motor activity could be a strategy used by ADHD children to stay awake and alert [60]. Subjective questionnaires completed by parents of ADHD children may not be suitable to assess sleepiness, which could be masked by hyperactivity. On the other hand, the Multiple Sleep Latency Test (MSLT) is considered the “gold standard” method for assessing alertness. The results of two studies [55], [61] using the
Sleep disturbances and psychiatric comorbidities
Psychiatric comorbid disorders, including oppositional disorder, conduct disorder, mood disorders, anxiety disorders, learning disorders, developmental coordination disorder, and tic/Tourette Syndrome, are frequent in ADHD [63]. Most of these psychiatric disorders might be associated with significant sleep disturbances, from a subjective and, less consistently, objective standpoint [64]. In consideration of the impact of psychiatric comorbidities on sleep, we suggest to systematically evaluate
Effects of medications on sleep
Psychostimulants (MPH, amphetamine, and lisdexamfetamine dimesylate) are the first-line, US Food and Drug Administration approved treatments for ADHD, followed by the non-stimulant atomoxetine (ATX). However, non-approved drugs, such as bupropion, tricyclic antidepressants, alpha-agonists, and modafinil, are also used [63].
It has been suggested that stimulants used in the treatment of ADHD lead to sleep disturbances. In particular, it has been reported in some studies that stimulants have
Conclusion: evaluation of sleep issues associated with ADHD/ADHD symptoms in clinical practice
Although a lot of work has yet to be done, current evidence and clinical practice suggest that, even if ADHD is not purely a result of sleep disturbance, it is conceivable that, at least in some children, the condition is a “24-hour” disorder, and that sleep disruption caused by increased nocturnal activity contributes to daytime symptomatology. Bearing this possibility in mind, the relationship between sleep disorders and ADHD should be considered by healthcare practitioners as part of the
Future perspectives
There is increasing evidence of alterations of sleep in children with ADHD, albeit at present there is still a lack of evidence on the most effective and safe treatment strategies (both pharmacological and non-pharmacological). Looking ahead, one of the most important issues in the research on the relationship between ADHD and sleep disturbances is to conduct methodological sound studies controlling for the possible confounding effects of psychiatric comorbidities and ADHD on sleep variables.
Disclosures
The authors have no relevant financial relationships to disclose.
Disclaimer
This article discusses unapproved usages for a number of drugs. Please note that neither the authors, nor the publishers, nor any sponsoring company endorses the use of any drug or device in a way that lies outside its current licensed application in any territory.
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