Some users find that they initially sleep an hour or two longer. After a few weeks, they sleep fewer hours but more efficiently.

What About Tolerance?
No formal studies have been done in humans regarding this issue. The use of most pharmaceutical sleeping medicines is known to lead to tolerance. Higher and higher doses are often needed.

Tolerance to melatonin is infrequent. Less than a tenth of my patients or survey respondents felt the need to take higher doses. Jerry, a 67 year old chiropractor from Miami, tells me, "I've been using 1.5 mg of melatonin regularly for 7 months. It seems to be as effective now as the first few nights." Tolerance is even less frequent in those who do not use melatonin every night, but take breaks once in a while.

I have, though, come across individuals who became tolerant to melatonin. Loretta, a 46 year old insomniac from Portland, Oregon found that melatonin stopped working for her when she took 9 mg every night for 10 months. Were melatonin receptors in her brain downregulated? A 1993 study in rats found regular supplementation decreased the number of melatonin receptors in the brain (Gauer). Will regular, high dose melatonin desensitize our brain to this hormone? I tell all my patients and melatonin users to use this supplement at most every other night, and in low doses, until we learn more about the question of tolerance.

Are There Withdrawal Symptoms?
Abruptly stopping prescription sleep medicines after chronic use can often result in sleep disturbances for a week or two. For some it takes longer. Data from my surveys suggest that withdrawal symptoms from the abrupt discontinuation of short-term melatonin use are uncommon. There is little or no insomnia the night following discontinuation, and any disturbances are corrected within a few days.

A few of my patients have noticed that they sleep just as well, or even better, the night following the use of melatonin. It seems that sometimes there is a slight carry-over effect.

Steve Dyer, 38, a software engineer from Cambridge, Mass., writes, "I find that melatonin is very effective at helping me get to sleep. Originally, a single lozenge was all that I needed, but I found that 4 lozenges worked better. I go to bed on time, and wake up on-time, refreshed.

"I used 10 mg of sublingual melatonin, four 2.5 mg lozenges, for several months. Upon stopping it, I had no rebound insomnia at all."

It's still too early to tell whether suddenly stopping melatonin after a few years of regular, nightly use will lead to withdrawal symptoms.

Many of our current uncertainties about the use of melatonin will no doubt be answered by the high interest in this supplement which is generating a great deal of research. Marilyn Elias, who wrote the December 20, 1995 article in USA Today, reports that the National Institutes of Health is spending $5 million a year on 57 melatonin studies, mostly about sleep and the body clock.