I took melatonin for years (low dose 500mcg). In retrospect, after taking melatonin I don't recall any dreams. I'd only dream after not taking it for a day or two then taking a dose of melatonin.
About two weeks after stopping melatonin altogether, I now recall dreams every night. Stopped taking it due to insomnia getting worse and worse and figure I'd see what would happen without it. First week was rough, back to normal after that.
Meaningless anecdote about what is most likely placebo, but I found it a bit interesting. Forgot what it was like to dream every night. Not planning on taking it again.
I take a mix of melatonin, l-theanine, and 5-htp almost every night to go to sleep, and I've definitely found that if I don't take it for a couple days (usually Fri and Sat night) then take it again, my dreams are overly vivid and memorable.
While I'm on it, they're pretty suppressed. I used to take 10mg of melatonin every night and the effects were the same I'd say, so it doesn't seem to matter on dosage.
About two weeks after stopping melatonin altogether, I now recall dreams every night. Stopped taking it due to insomnia getting worse and worse and figure I'd see what would happen without it. First week was rough, back to normal after that.
Meaningless anecdote about what is most likely placebo, but I found it a bit interesting. Forgot what it was like to dream every night. Not planning on taking it again.