Is Melatonin good for sleep quality?

The evidence points that way, though it's not yet conclusive. Melatonin is among the most heavily meta-analyzed sleep supplements, and the picture that emerges is a real but modest effect that varies by population. That's reflected in an evidence score of 62/100 for its role in sleep quality, drawn from 8 studies, with an estimated impact on longevity rated limited (30/100).