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.

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.

People went to bed when the sun went down and they woke up when the sun came up. That's what our bodies are naturally programmed to do. However, with all the new stresses in life with electricity, with technology, we tend to override that system and we'll stay up later and we'll get up earlier or later, and we use alarm clocks, we use the light.

Workplace accidents with people who are sleep deprived or people who work shifts and they don't get the right amount of sleep during the day or at 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.

There are some that are - REM Behavior Disorder, we'll see some court documented cases. And they really need to have a thorough evaluation with a sleep specialist.

In general, there are patients with insomnia who - many patients with insomnia will actually over report the lack of sleep that they are getting.