Melatonin did not clearly speed up falling asleep after flights
Across three jet lag trials it shaved about 5 minutes off the time to fall asleep, a gap chance could explain.
What the study found
Time to fall asleep after flights did not clearly shorten on melatonin
Pooled across three jet lag trials, melatonin users fell asleep about 5 minutes sooner than placebo users, a gap chance could explain. The review concluded melatonin had no proven use for jet lag, having measured only how fast and how well people slept. That verdict covers sleep alone.
The caveat · Could be about 13 minutes faster
The data allow anything from about 13 minutes faster to 3 minutes slower, so a modest gain is not ruled out. The review's headline figure pooled jet lag with shift work and sleep deprivation. Two single trials, the first among them, did report faster sleep onset on melatonin.
What we don't know
One review found melatonin did not speed falling asleep and called it unproven for jet lag; another found overall jet-lag ratings lower. They measured different things, so whether it helps sleep onset in particular is still open.