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.

So a lot of people who work rotating shifts and they work at night, their bodies are set to want to be awake during the day and sleep at night. So there are some people who have a lot of trouble adjusting their rhythms and they have trouble working the night shift, they're sleepy, they're drowsy driving home.

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.

So someone who is a child usually goes to bed about 8:00 or 9:00 at night, but then when they have a circadian rhythm shift, it shifts later. And this is natural. And they start to go to bed at 11:00, 12:00, 1:00 and they want to sleep later. So we see this a lot in teens.

For some people they say, it's about wish fulfillment, it's about the things you are never able to do in your day you are actually fulfilling at night. There are other people who will say that it's actually telling you something.

Night terrors are in deep sleep, and they're more common in kids, as are nightmares, but what happens in a night terror is like a flash - we think a flash of some image or something happens in the brain. We don't really quite know what. And it usually ends up with the child screaming almost like screaming bloody murder. It's very scary for the parents or whoever else is around.

We have other opposite problems with circadian rhythms that can happen when you - a lot of times with older adults. They start to go to bed at 6:00, 7:00 at night and they wake up at 2:00 in the morning. And they're rhythms actually shift earlier, but sometime it can just kind of miss the mark and shift too much earlier and that's when we need to treat it with bright light.