Responses seem variable to melatonin. I have SOME response, mainly in that it causes really, really REALLY vivid dreaming (when I've combined it with the gently sedating herb valerian, which itself does that to me, my dreams sometimes become so realistic and intense they were indistinguishable from being awake). It doesn't seem to improve sleep latency however.
All that said, I am, in general, fairly tough to sedate, even without a pre-existing tolerance
to benzos, etc. it generally took fairly heavy doses before sufficient effect became noticeable. This only applies to the sedative/hypnotic properties though, and not to anxiolytic or myorelaxant effects.
I do have a tolerance to benzos etc. now though most likely, as the anticonvulsant drug I take to suppress myoclonic attacks (chlormethiazole, a halogenated vitamin B1 derivative having barbiturate-like sedative-hypnotic effects) will nearly certainly be crosstolerant with other GABAergics. Melatonin was no good in my case at inducing sleep, although sleep quality seemed better, before I started on the chlormethiazole.
On the other end of the scale, my friend uses it to help her Kanner's autie son sleep, and she says that after it he is out within 15-20 minutes.
I figure though that I may as well give melatonin another go sometime. Its nonaddictive, not too expensive, and the lucid dream inducing effect it had on me was quite enjoyable. I recommend trying the combination of melatonin and valerian extract (the latter available at health food shops...stinks something awful though, make sure to go for capsules not tincture, I couldn't imagine trying to swallow valerian in any form that actually gets to touch one's tastebuds. Ew. Stinks like putrid socks and cat piss. Around 10-15mg melatonin, and a gram or so of valerian extract in capsules did the trick for me. The oneirogenic effect of valerian seems to exhibit a rapid tachyphylaxis however)
