So you have Sleep Stage One, Two, and then Three/Four. One is a little bit lighter stage of the quiet, non-REM sleep and then Three/Four is really deep, deep sleep. And what you want is, you actually want a number of - you want to go through all of these stages throughout the night.

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.

So you have Sleep Stage One, Two, and then Three/Four. One is a little bit lighter stage of the quiet, non-REM sleep and then Three/Four is really deep, deep sleep. And what you want is, you actually want a number of - you want to go through all of these stages throughout the night.

In general, there are patients with insomnia who - many patients with insomnia will actually over report the lack of sleep that they are getting.

There's some debate as to whether you need to awaken from them because there are some patients who are actually starting to say, "I had these horrible nightmares, but I never woke up from them." But they can still recall them when they get up in the morning. So there's still some debate in the field.

When you are more awake at nights, they'll toss and turn, they'll think more, they get frustrated. And when that starts to happen, you really don't sleep even more because you're making your body tense and your mind is getting more and more active.

So, more times than not, but not every time, it can be linked to a medical problem, such as menopause, cancer, chronic pain, it can be linked to anxiety and depression. Those are the more common causes.