And you cycle throughout so that you do about five to six cycles throughout the night. And we spend more time in REM later on in the night than we do earlier on.

Well, the actual function of the brain, not so sure yet. There's a lot of different theories about it, but when you talk about psychologically in your brain, a lot of people with insomnia, though not all, report that they can't turn their minds off.

Workplace accidents with people who are sleep deprived or people who work shifts and they don't get the right amount of sleep during the day or at night.

Decrements in attention and concentration, being able to learn more efficiently, that's just not as good. Also, there are motor vehicle accidents, workplace accidents, we see that a lot.

So people only focus on getting the really deep sleep, but in reality, we spend almost 60% of the night in the stage two sleep.

We've looked at sleep diaries of patients with insomnia, and they'll say that they don't sleep for one or two days. And the body actually has a natural function, after about the third day to start catching up and you get a little bit more sleep the third night. And that's usually what I tell my patients.

Now there's some night terrors that happen in adults. And if it starts as an adult and you've never had them before, then there might be other things that are happening; it might be anxiety, depression, stress. And that's when you might have more of a thorough psychological evaluation.