When it comes to the reason why we have nightmares, we're still debating that. It's a new area of research, nightmares. And the way I like to think about it is, our brain - we have stress during the day and our brain needs to learn to process this stress.

There are people who have repetitive nightmares. And what happens is their brain is trying to process the stress and help their brain actually deal with what happens if this stress happens again, so their brain's preparing them to deal with it in case the stress happens again, but it's so scary that they awaken from it.

So, it's not every patient that I see, but I'd say a good 70% to 80% of the patients when they go to bed it's like a stereo is playing at an 11 or 12 and they can't turn it down, at all. So it makes it very hard for their body to down regulate to be able to go to bed at night.

Some patients will report that they have sleep paralysis. If we see sleep paralysis alone and nothing else, we don't really think all that much of it, but if we see other symptoms, then it might be a red flag for something else that's going on.

Nightmares are distinctly different from dreams in the way that people feel them and experience them. So a lot of people think that a nightmare is something where something is chasing them and you have to wake up screaming. Yes, that's one of the more common nightmares that we see is the person chasing someone or they're being chased.

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.

Now circadian rhythms become very interesting and problematic for patients because when you become a teenager, your rhythms actually tend to naturally shift.