? Anybody else, but me, have qualms about unregulated melatonin consumption?
I have seen some altered hormonal cycles change for the worse in individuals who took melatonin. When the normal, opposite, interplay between levels of adaptative "stress" hormones & melatonin is tinkered with it is not always a free ride.
In prostate cancer often the melatonin levels are measurably high in a late day time period, when healthy individuals normally do not have this hormone elevated. ( This example is an empirical peculiarity of one diseased state & not suggested as the cause of any pathology.)
My observation has been that a hormonal cycle shift, due to melatonin rising when it shouldn't , is a noticeable "crash" of stress hormones in the late afternoon (in patients with NO underlying blood sugar problems, ie: not a hypo-glycemic induced symptom).
If I could have measured their melatonin levels during this time to consolidate my theory it would have been ideal science, I know ( OK, no Nobel prize nomination for now).
Nor was/am I equipped to measure stress. I know in Autistic research that stress hormones in childrens' saliva is considered a real time measurement (if any of you have that technology).
As is, with the suspension of melatonin supplements, in these individuals there seems to no longer be a regular "crash" you could almost set your clock by. (Crash manifestation included all the worst symptoms of a come down from "fight or flight" stress hormones - shaking, crying, irritability, fatigue, etc.)

I agree that there's no free ride when it comes to any supplement or drug for relaxation/sleep, and there almost certainly has been no real study of "Drank" to see what the safety and effectiveness profile are.

Journal, Nature Genetics , 7 Dec. 2008 layman's synopsis:
Too many Melatonin 1B receptors is a common genetic variation across the population spectrum.
Melatonin hormone in circulation is part of Type II Diabetes' Beta cell pathology.
Excess Melatonin inhibits these Insulin hormone releasing cells, causing incomplete response to the presence of glucose (a.k.a. blood sugar).
With Melatonin binding to it's overabundant receptors in the Beta cells the blood sugar rises uncontrolled. This means not enough Insulin hormone is getting released into circulation to do it's job of driving the glucose out of the blood stream & into storage inside body cells.
Type II Diabetes is also frequently referred to as "Adult Onset Diabetes" & by some as "Hyper-insulinism".

All I know is that I tried melatonin briefly at one point and it seemed to make me worse, so I immediately stopped taking it.

The connection with diabetes is interesting.

The relationship between melatonin and insulin secretion is complex, and involves such things as shifts over the course of a day in how much insulin is produced. There may be genetic alterations in melatonin receptors that affect onset of diabetes, but it hasn't been shown yet that melatonin use for sleep disorders causes diabetes. In fact, there's some preliminary evidence that supplemental melatonin taken with a diabetes drug may improve blood sugar control.

At this point with the limited evidence we have, people are probably wise to avoid chronic, long-term use of melatonin for sleep disturbances.

Melatonin combined with "anti"- diabetics isn't a do-it-yourself treatment.
Expect to see drugs developed targeting pancreatic isles' Melatonin receptors.
(Side effects to only be guessed at now.)
I always have trouble getting poly-symptomatic people to understand that there are multiple hormonal cycles that can be shifting throughout the day.

I think that since sleep disturbances can be a symptom of so many dis-eases; using any medication herbal or not on a long term basis for sleep disturbances is a bad idea.

"Melatonin combined with "anti"- diabetics isn't a do-it-yourself treatment."

Agreed. The preliminary evidence indicating that supplemental melatonin might help a drug's action was referring to metformin, a prescription medication used in type II diabetes. Anyone on a prescription drug who's also taking supplements needs to consider how they might affect metabolism of the drug, and tell their physician what they're taking.

For inquiring minds:
University of California satellite TV now is online with continuing education for medical field:
www.uctv.tv/meded/
New York Times weekly science section is online with frequent layman medical reports:
www.nytimes.com/pages/science/
Incidently, N.Y.T.'s Jan. 7, 2009 science edition has content Herbalism forum partly discussed in piece titled:
"Babies Know: A Little Dirt Is Good For You."