Do melatonin supplements really help people sleep?

Sora Song in Time Magazine:

Millions of jet-lagged and sleep-deprived Americans–citing countless self-help articles–insist they do. But the scientific evidence has been slim. There’s no question that the hormone helps the brain tell a.m. from p.m.–regulating sleep cycles and circadian timing–when it is produced naturally by the body at night. What was lacking was clear evidence that taking melatonin in supplement form had the same sleep-inducing effect.

That’s why there’s so much interest in a study in the current issue of the journal Sleep. Researchers at Brigham and Women’s Hospital and Harvard Medical School set out to test melatonin’s effects and found that the supplements can indeed be a potent sleep aid–but only during daylight hours.

More here.