Most kids with autism have trouble sleeping — whether that’s difficulty falling asleep, or waking up many times during the night.

For that sizable group, here’s some welcome news: melatonin, the over-the-counter food supplement that some travelers use to shake jet lag, may help children with autism fall asleep faster, according to a report published last week.

In the study, children with autism or fragile X syndrome who took melatonin before bed fell asleep a half-hour earlier, and slept about 20 minutes longer, than kids taking placebo.

Melatonin is a natural hormone. The brain releases it to lower body temperature and make us feel drowsy. A couple of reports have found that children with autism have unusually low levels of melatonin in their blood, which seems like a plausible explanation for why they have trouble getting to sleep.

The new study isn’t the first report of melatonin’s soporific effect on people with autism. Last year, another team found that melatonin improves sleeping patterns in about 80 percent of children with autism who suffer from insomnia.

Melatonin doesn’t help everyone, and sometimes it causes kids to wet the bed or feel drowsy in the morning. But that’s nothing compared to the dizziness, nausea, and other harsh side effects of the scant few drugs that doctors use to treat symptoms of autism.

Children with autism are notoriously irritable, aggressive and unsociable — but so are most of us when we don’t get enough sleep. Maybe melatonin will give these kids not only more restful nights, but more restful days.