Anecdotal: DS12 has taken melatonin during school year (when he takes stimulant med) for three years and he entered puberty early-ish (has facial hair already, despite small stature). DD11 takes it occasionally (no meds, but terrible sleeper) and entered puberty early-ish as well.

I had never heard about this potential side effect. In our case, if it *did* delay puberty, I'm grateful.