Kids with ADHD sleep less well than other kids. Why is this?
Before we address this question, let’s back up and ask some preliminary questions:
- Is it true that kids with ADHD sleep less? Yes, the evidence suggests this is true.
- Is ADHD a real disorder? Some experts claim there is no such thing as ADHD. They argue that what we call “ADHD” is causing the sleep problems we see.
A study published in the June issue of the Journal of Sleep Research presents some evidence that might help answer these questions.
These Danish investigators found that there is something funny about the way kids diagnosed with ADHD sleep. There are some notable and very important features of this study. The first has to do with the way researchers recruited families to participate.
Parents and pediatricians referred children to a clinic because of problems with attention. None of them had a diagnosis of ADHD. They filled out questionnaires and agreed to let their children have sleep studies. They did all of this before they had a diagnosis. In other words, the subjects were “blinded” to their placement in the study. This type of blinding helps remove any unconscious bias the parents may have had when answering the questions. By the end of the study, investigators had data from 76 children, average age nine. That’s not a huge study, but it is the largest study of ADHD sleep patterns to date.
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Parents kept a 1-week sleep diary, logging hours of sleep and various other data points. Then investigators fitted children with take-home sleep study (polysomnography) machines. Though not the most comfortable devices, most children tolerate them well. The machines measure brain wave activity, breathing and oxygen levels, among other things. Finally, researchers invited the children to a sleep lab to perform a Multiple Sleep Latency Test (MSLT). It’s a long name for a test that simply measures how long it takes you to fall asleep when you take naps during the day.
The investigators also diagnostic tests for other disorders, such as autism, anxiety, and depression. They also performed intelligence tests and excluded children who scored an IQ less than 70. Investigators did not explain why they excluded mentally retarded children from the study. No part of the exams required any cognitive ability on the part of the child at all.
It turned out that 55 percent of the children with ADHD had some other diagnosis as well, called a “co-morbidity.” Before the study started, the investigators had guessed that children with multiple diagnoses would have more trouble sleeping.
To their surprise, investigators found that children with multiple diagnoses had the same sleeping patterns as children with only an ADHD diagnosis.
Children with ADHD did not sleep as long as children in the control group. On average the 76 children with ADHD slept 501.9 minutes (about 8 hours and 20 minutes). Control children slept an average of 543.6 minutes (just over 9 hours).
Children in the ADHD had more sleep cycles (6.2) than the controls (4.4). In other words, the rise and fall of sleep, also called “sleep architecture” was significantly different.
It takes 10 minutes longer for children with ADHD to fall asleep at night, compared with control children.
By contrast, when taking the MSLT test, children with ADHD fell asleep faster, suggesting they are sleepier during the day despite being reported as more hyperactive and restless.
Taken together, these results suggest that the sleep of children with a diagnosis of ADHD may sleep differently than other children. What does this mean?
Is ADHD a problem with the part of the brain that controls attention and alertness? This has been the theory for decades. This theory is the basis of ADHD treatment with stimulants.
Sleep is more complex than this. Many parts of the brain are involved. Could it be that the symptoms of ADHD are caused by some other oddity in the way the brains of ADHD kids work?
The results of this study are interesting, but raise more questions than they answer. At the end of the paper, investigators admitted that “it remains unclear whether sleep disturbances in ADHD are an aetiological (causal) factor, a co-morbid disorder or the result of an overlapping neurodevelopmental disorder of the brain.” In other words, the investigators cannot say whether kids with ADHD sleep poorly, or whether kids who sleep poorly have symptoms of ADHD.
This study provides another nail in the coffin of the “chemical imbalance theory“. This theory stated stated that ADHD was caused by too little stimulatory neurotransmitter in the brain.
Investigators also avoided making an obvious point: If symptoms of ADHD correlates with a sleep disorder, then giving amphetamine-based medications to children probably will not correct the underlying problem. The opposite is more likely. Indeed, insomnia is a well-known side effect of Ritalin and other ADHD drugs.
And lack of sleep never helped a distractible child.