[Blueflag]

Rest assured, this is a correlation study.

One has to ask, why are they having trouble sleeping and feel the need to take melatonin?

Therein lies the root cause, not the melatonin.

[ConservativeMind]

It was matched to people who had insomnia, but had used prescriptions or other methods, and not melatonin.

[Cold Heart]

Good point. Melatonin is also one of the recommended supplements for fighting long covid vaccine.

[heartwood]

Among adults with insomnia, those whose electronic health records indicated long-term melatonin use (12 months or more) had about a 90% higher chance of incident heart failure over five years compared with matched non-users (4.6% vs. 2.7%, respectively).

Both the melatonin users and the non-melatonin users had trouble sleeping.