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 when it comes to circadian rhythms, it's a clock that's basically programmed in our body. So if you think back to times when people lived on farms and we didn't have electricity.

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

So when you go to sleep at night, if you're someone who hasn't had any sleep deprivation, you have a very normal sleep pattern, what we tend to see is that, in adults, they go to bed and they start off by going into the deeper stages sleep.

We think is happening in the brain, the way I like to think about it is, it's almost like, you're brain is going through all these stages of sleep and it's developing in children so fast that it's almost like you're shifting gears in a car. And at some point, you actually stall out a little bit, and that's kind of what happens during a night terror.

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.