Treatment of sleep disorders in children often leads to substantial improvements in behavior and cognition, as well as a significant reduction in irritability, bad moods, anger and fear.

Doctors should consider that possibility before prescribing Ritalin and other ADHD drugs, they suggest.

An estimated 8 percent of US children suffer from ADHD, according to the US Centers for Disease Control, and more than half of them are being treated with drugs.

ADHD is characterized by overalertness and nervousness, with affected children being fidgety and overstimulated. Paradoxically, the use of stimulant medications like Ritalin seems to be the most effective method for treating ADHD symptoms in the majority of children.

Fighting to Stay Awake?

Dr. Giora Pillar wondered whether some children diagnosed with ADHD might simply be sleepy. Their excessive motor activity could be a tool to stay alert, he conjectured, which might explain the effectiveness of stimulants that increase activity in the central nervous system.

"Sleepy children, unlike sleepy adults, may demonstrate hyperactivity and attention-deficit behavior rather than excessive daytime sleepiness," Pillar explained.

"This theory is supported by parental reports that children, when extremely tired, tend to be cranky, overactive, angry and aggressive," he pointed out.

Sleep Apnea, Limb Movement Disorder

Pillar and colleagues studied 66 children with an average age of 12. Of these, 34 already had been diagnosed with ADHD, and the rest served as a control group. The ADHD-diagnosed children had significantly higher levels of sleepiness during the day than those in the control group, the researchers found.

Half of the test subjects with ADHD (vs. 22 percent of the control group) suffered from some degree of sleep-disordered breathing, such as sleep apnea, which is characterized by interruptions in breathing that last 10 seconds or more, occurring at least five times per hour during sleep.

Fifteen percent (vs. none in the control group) had Periodic Limb Movement Disorder (PLMD), which is relatively uncommon among children.

Studies have shown that treatment of these sleep disorders in children often leads to substantial improvements in behavior and cognitive achievements, Pillar said, as well as a significant reduction in irritability, bad moods, anger and fear.

For example, school performance, which is low in children with sleep apnea, has been found to improve markedly following the removal of adenoids and tonsils to correct the disorder.

Enforce Good Sleeping Habits

The researchers urge parents of hyperactive and attention-deficit children diagnosed with sleep disorders to have breathing irregularities and limb movements treated, to enforce good sleeping habits, and to avoid giving them caffeinated drinks at night.

Only if these steps do not work, they say, should parents consider medication for ADHD.

The researchers' findings originally were published in the February 2004 issue of the journal Sleep.