In answer to both previous posters, sleep is not a simple process. It has successive stages that normally follow each other in a pattern. The brain needs this to regulate itself and to 'recover' its cognitive functions from the efforts of the previous 24 hours. REM, or 'rapid eye movement' is an early stage associated with dreaming, which itself is exceedingly important to clearing out the 'cobwebs'. When we interrupt our sleep, whether from crying infants, to sirens, to having to void one's bladder, to simply tossing and turning, or due to the actions of drugs on our brains, as just a few examples, we have an interruption. This is to be avoided to the extent possible. That is why apnea must be controlled. That is why some sleep aid use might be necessary, even if just one night in every five or seven. This is what works for me. Most nights, using my CPAP machine effectively, but with no other aids, I get 6+/- hours per night, often with three to five sleep cycles (including REM cycles). This gets at least a good score, sometimes excellent if I happen to get another bonus 30 minutes. But, when I get less, or when my sleep cycles number only three per night, I begin to lose ground, make more mistakes, get grumpy, fall asleep after supper....the usual old man syndrome. Melatonin, the one or two times I take a single 3mg tablet, the sleep is almost always extended, and I get at least one more dream cycle. This is very good for the brain. It isn't nice when we have horrible dreams..........................but............................they're DREAMS!!! If they don't awaken you fully, and you can fall back asleep, they still provide the function that the brain needs. The other thing is that the brain might be flooding itself with dreams because of the poor quality sleep it has had for months/years. Having nightmares and highly vivid dreams is widely reported in the literature anecdotally by patients when their sleep improves. This is true only for new users of CPAP machines for apnea, but also for those who have no apnea but do have anxiety or other conditions that interfere with sleep and who try one or more sleep aids. Melatonin is no different that way.