Really if it's an hour or two after you've fallen asleep because you're in such a deep sleep at that point.

There are some people who believe that dreams really are just kind of a throwaway thing. They are just a way of your brain processing what's happening during the day, but there's really no meaning to them; a lot of imagery of just flashes of what happened.

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.

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.

So when you're in REM sleep, your brain is very active, our body is quiet, but your brain is really processing a lot of things, a lot of emotions; we dream the most in REM sleep. And then you go back down in the deep stages, and so on and so forth.

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

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.