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 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 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.

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.

Really, a nightmare just really has to evoke some sort of, we call it, dysphoric emotion or something uncomfortable. You could be sad, you could be unhappy; you could be scared, anxious. But traditionally, the definition is you have to awaken from this nightmare.

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.

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.