We're not really sure why it [broken circadian rhythm] continues, but when they become adults, we usually have to treat it because many people need to get up early to go to work and they can't be sleeping until 11:00 or 12:00. So we use treatments like bright light therapy, melatonin, things like that that are very effective.

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.

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.

It's uncommon, but there are some people who just have a delayed circadian rhythm and they just - they sleep better during the day then they do at night. So they've - a lot of those people with delayed sleep phase disorder they start to work in bars, they work some of the late night shifts, they sort of adjust to doing it more and more as time goes on.

There's some debate as to whether you need to awaken from them because there are some patients who are actually starting to say, "I had these horrible nightmares, but I never woke up from them." But they can still recall them when they get up in the morning. So there's still some debate in the field.

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.

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.