There's confusional arousals, there are states in deeper sleep that can happen where people will go and they'll disappear and they'll take on some other persona. They'll commit some crime, but it's all when they are in a very deep stage of sleep. So you really need to have a very thorough evaluation.

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.

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.

We haven't really - it's harder for us to set those rhythms. So it's really important to keep a steady bedtime and wake time to really lock in those rhythms.

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.

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

So, sleep deprivation, and sometimes an insomnia, which is a little bit of a different form, but just getting a lack of sleep, can lead to a number of different decrements.