Three milligrams of melatonin at bedtime can effectively treat sleep problems in children with autistic spectrum disorder, fragile X syndrome, or both, according to a study reported in the current issue of the Journal of Clinical Sleep Medicine.

"Melatonin can be considered a safe and effective pharmacologic treatment in addition to behavior therapies and sleep hygiene practices for the management of sleep problems in children with autistic spectrum disorder and fragile X syndrome," the study team concludes.

Melatonin is a naturally occurring hormone, derived from the amino acid tryptophan. The hormone is important in regulating circadian rhythms, or the "sleep wake" cycle, and the reproduction cycle in mammals.

Fragile X syndrome is an inherited form of mental impairment resulting from a "fragile," or broken site, on the X chromosome. The syndrome affects 2 to 5 percent of those with autism spectrum disorder, and symptoms of autism are common in children with fragile X.

Sleep problems are reported in up to 89 percent of children with autism and 77 percent of children with fragile X syndrome, Dr. Beth L. Goodlin-Jones, of the Medical Investigation of Neurodevelopmental Disorders (M.I.N.D.) Institute at the University of California Davis Health System in Sacramento, and colleagues note in their report.

In a 4-week study, 18 children, ranging in age from 2 to 15 years, with autistic spectrum disorder and/or fragile X syndrome received either melatonin (3 milligrams) or placebo each night for 2 weeks. The children then "crossed over" to the other treatment group for 2 weeks.

Data from 12 children who completed the study showed that treatment with melatonin was associated with significant improvements in total night sleep durations, sleep latency times and sleep-onset times.

Specifically, Goodlin-Jones and colleagues report that the average night sleep duration was 21 minutes longer with melatonin than with placebo, the sleep-onset latency was 28 minutes shorter, and the sleep-onset time was 42 minutes earlier.

"Sleep onset problems at the beginning of the night are very troublesome for children and their families," Goodlin-Jones noted in a prepared statement accompanying the study. "Sometimes children may take one to two hours to fall asleep and often they disrupt the household during this time."

"The results of this study," she and her colleagues conclude, "suggest that melatonin is an effective treatment for sleep problems in children with autistic spectrum disorder and fragile X syndrome, a finding that is consistent with previous studies of children with autistic spectrum disorder and developmental disabilities."