Sleep in children with attention-deficit hyperactivity disorder (ADHD): a review of naturalistic and stimulant intervention studies

Abstract

Attention-Deficit Hyperactivity Disorder (ADHD) is the most common behavioral disorder of childhood. Multiple clinical and research reports suggest extensive sleep disturbances in children with ADHD, however, current data is contradictory. This paper reviewed 47 research studies (13 stimulant intervention and 34 naturalistic) on ADHD that were published since 1980. The main objectives of this review were to provide pediatric clinicians and researchers a clear and concise summary of published sleep data in children with ADHD, to provide a more accurate description of the current knowledge of the relationship between sleep and ADHD, and to provide current information on the effect of stimulant medication on sleep. Twenty-five of the reviewed studies used subjective reports of sleep, six were actigraphic studies, and 16 were overnight polysomnographic sleep studies (two of which also included Multiple Sleep Latency Tests). All participants were between the age of 3 and 19, and 60% were male. The results indicate high rates of parental reports of sleep disturbances in medicated and unmedicated children with ADHD, however, the majority of these findings have not been confirmed by objective sleep data. Although, agreement among objective studies is not absolute, the data suggest increased nighttime activity, reduced rapid eye movement sleep, and significant daytime somnolence in unmedicated children with ADHD when compared to controls. Data also suggest a possible increased prevalence of periodic limb movements in sleep in children with ADHD, however, little differences in sleep-disordered breathing. The limited number of studies, small and heterogeneous samples, and other methodological limitations make definite results difficult to determine. Future research will need to further clarify the relationship between sleep and ADHD and the effects of stimulants on sleep of children with ADHD.

Introduction

Attention-Deficit Hyperactivity Disorder (ADHD) is the most commonly diagnosed behavioral disorder in childhood; estimates of community or primary care samples suggest rates between 3 and 12% of school-aged children.1., 2., 3. ADHD is a highly heritable disorder with anywhere from 4:1 to 9:1 boy:girl ratio.1., 4. The consequences of ADHD can be quite detrimental to the developing child as the hyperactive, inattentive, and impulsive symptoms have been associated with poor academic performance, reduced occupational success, and age-inappropriate psychosocial development. According to the 1998 National Institutes of Health Consensus Statement on the diagnosis and treatment of ADHD, this condition has become a clear and costly public health problem, with frequent involvement of medical and mental health, educational, and legal institutions.² Unfortunately, the 2004 International Consensus Statement on ADHD and Disruptive Behavior Disorders indicates that despite the availability of effective treatments for ADHD, the lack of awareness and/or understanding of ADHD by the above institutions have led to the inadequate treatment and management of this condition.⁵

The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) identifies three ADHD subtypes: predominately hyperactive–impulsive, predominately inattentive, and a combined subtype.¹ Identification and report of ADHD subtypes varies greatly across research studies with most reports reviewed here having collapsed the subtypes into one ADHD group rather than analyzing data across subtypes.

Various treatments have been attempted for the management of ADHD, including but not limited to stimulant, psychotropic, and antidepressant medication, homeopathic treatments, psychosocial treatments, and dietary management. In 2000, the American Academic of Pediatrics (AAP) published the ‘Guidelines for the Treatment of ADHD’³ state that stimulant medication and/or behavior modification are the most effective treatments for ADHD.

Central nervous system (CNS) stimulant medications have become the first line treatment for ADHD in clinical settings and accordingly are the most researched treatment for ADHD. Most research studies have indicated stimulant treatment is effective in approximately 70–90% of child cases of ADHD.2., 6., 7., 8. The first treatment studies examined the effectiveness of traditional immediate release (IR; short-acting) stimulants, which are typically absorbed within 30 min, peak within 1–3 h, and are completely dissolved within 6 h. The short half-life of IR stimulants (e.g. methylphenidate [MPH; e.g. Ritalin], dextroamphetamine [DEX; e.g. Dexedrine]) requires children take this medication either twice (b.i.d.) or three times (t.i.d.) a day. Recent pharmacological developments have introduced extended release (ER; long-acting) stimulants (e.g. methylphenidate [e.g. Concerta], dextroamphetamine/levoamphetamine [e.g. Adderall XR]), which gradually release the active drug into the child's system over the course of several hours and are completely dissolved within 12 h. ER stimulants have become increasingly popular because the child only needs a once daily dose, usually taken in the morning. However, as ER stimulants are typically fully dissolved by the late afternoon, the result may be reduced effectiveness of the drug in the early evening and night.

The presence of sleep problems in children with ADHD has long been studied. The first scientific report of sleep problems in children with ADHD was published in 1971 by Small and colleagues.⁹ The link between ADHD and sleep disturbances has also been evidenced by the addition of sleep problems as one of the ADHD diagnostic criteria in the DSM-III.¹⁰ Despite the removal of the sleep problem criteria in updated editions of the DSM, clinical and research reports of sleep problems in ADHD remain frequent.

The decision to write this review was based on a search of the literature and which revealed four published reviews on sleep in children with ADHD in the past decade. Two reviews were in French,11., 12. one in German,¹³ and one in English.¹⁴ An examination of these reviews' bibliographies indicates an extensive and comprehensive overview of the literature. However, there are several main differences between the above reviews and the current one. First of all, three out of four reviews are not in English and may therefore not reach a larger population of readers. In addition, the review by Corkum and colleagues, although excellent, was published in 1998, with the most recent study included published in 1996. There has recently been a significant increase in research on sleep disturbances in stimulant-medicated and unmedicated children with ADHD. This review includes an additional 24 studies (from 1996 to the present), which were not included in the Corkum et al. review. One additional distinction between this review and previous ones is the exclusion of studies prior to 1980, which we believe may have significant methodological issues, which may affect the interpretation of the results (see below for specifics).

There has also been recently increased concern that sleep problems in children with ADHD may be a primary condition which results in secondary symptoms of hyperactivity and inattention, rather than ADHD being the primary condition associated with specific sleep problems. The purpose of this review is to provide clinicians with a concise summary of the literature on the relationship between ADHD symptomatology and sleep and the effects of psychostimulants on sleep in children with ADHD. With this information, pediatricians and pediatric sleep clinicians may be able to make more informed decisions regarding evaluation and treatment of sleep problems in this population. Furthermore, this review may inform researchers of additional important avenues for research.