Sleep Disorders Overlap With ADHD but Are Rarely Measured

What the research found

A standard ADHD assessment establishes that symptoms began before the age of twelve, that they appear in two or more settings, and that they impair functioning in both. Rating scales go to a parent and usually to a teacher, and other psychiatric conditions are screened for. Nothing in that sequence requires a question about sleep, and the review’s starting claim is that sleep disorders alongside ADHD are routinely overlooked and left untreated.

Dafna Wajszilber, José Arturo Santiseban and Reut Gruber, at McGill University and the Attention Behavior and Sleep Lab in Montreal, assembled what is known about that omission. Their review, published in Nature and Science of Sleep in 2018, drew together 39 studies from the preceding five years that measured sleep and ADHD in the same participants. It is a narrative review rather than a meta-analysis, so no result in it is pooled into a single figure.

Sleep problems are reported by a quarter to half of people with ADHD. Insomnia is the most frequent, described in 73.3 percent of children with ADHD against 20 to 30 percent of children generally, and in 67 percent of one sample of 268 adults with ADHD against 29 percent of controls.

Four other sleep disorders are also more common in ADHD, and each can generate the daytime symptoms an ADHD assessment records. Restless legs syndrome, an urge to move the legs that worsens at rest and in the evening, appears in up to 44 percent of people with ADHD, and restlessness and inattention by day are the ordinary consequence of a night spent needing to move.

Sleep-disordered breathing operates by a different route. A history of snoring or possible obstructive sleep apnoea in childhood is associated with a twofold difference in the odds of an ADHD diagnosis or symptoms. The proposed mechanism runs through repeated drops in oxygen and the arousals that fragment the night. Those insults alter the neurochemistry of the prefrontal cortex, the region most often invoked in accounts of ADHD.

Adults with narcolepsy are roughly twice as likely as controls to report a childhood ADHD diagnosis, and the excessive daytime sleepiness that defines narcolepsy can present as inattention and poor impulse control.

Which condition produces which cannot be settled from this literature, and the review says plainly that its shortage of longitudinal and experimental studies limited any account of direction. Its recommendation proceeds from that ambiguity rather than around it: a sleep evaluation at the initial ADHD assessment, and screening for sleep problems as a standing part of ongoing care.

What it means for you and your child

Stimulant medication belongs inside this question, and the evidence on stimulants and sleep points in more than one direction. An open-label study of 136 children with ADHD and 42 healthy controls found that extended-release methylphenidate reduced urinary excretion of a melatonin metabolite and lowered morning melatonin, which the review reads as a possible influence on chronotype. A much smaller open-label study, of ten adults, found methylphenidate raised melatonin levels and left the timing of its evening onset unchanged.

Measured against sleep itself rather than hormones, the findings diverge again. Among 41 children with ADHD, stimulant use was associated with no difference in sleep, and among the 268 adults, those receiving stimulant treatment had lower insomnia severity than those who were not. None of these studies examined dose, and none examined the hour at which a dose was taken.

Where a sleep disorder has been identified and treated, the daytime evidence is more encouraging. Removal of the adenoids or tonsils is first-line treatment for children with ADHD and sleep-disordered breathing. In a prospective study of 170 children who had the surgery and 150 healthy controls, older and obese children improved least, and symptoms of hyperactivity, inattention, anxiety and depression fell after surgery across the group.

A randomised trial of a distance-delivered behavioural sleep programme, in 22 children with ADHD and 39 typically developing children with behavioural insomnia, shortened the time taken to fall asleep and improved parent-rated attention and behaviour, with gains still present six months later.

The limits of that evidence are real. Most of the childhood sleep data come from parent report, adolescents are barely represented, and the daytime outcomes were defined too loosely to gauge how large the sleep-attributable impairments are. What survives is the frequency with which these conditions occur together, and the ease with which the symptoms of one are read as the symptoms of the other.

The review’s clearest practical statement concerns sequence. Where sleep disruption contributes to daytime inattention or executive difficulty, the authors argue, treating the sleep problem may be the appropriate first step, before or alongside a stimulant prescription rather than after one proves insufficient. Untreated sleep problems, they add, will likely reduce the efficacy of any intervention aimed only at ADHD symptoms.

That sequence gives a parent something specific to raise in a consultation. Before the next adjustment to a dose, you can ask the prescriber whether a primary sleep disorder has been looked for, and what would be done if one were found.