PBS's show Nova discusses dreams and depression.
PATRICK MCNAMARA: I think that we have more negative emotions during REM-related dreams because during REM sleep the amygdala is very highly activated, and the amygdala specializes in handling unpleasant emotions like intense fear or intense anger or aggression.
NARRATOR: Finally the night is over, but the experiment has more to reveal. McNamara is beginning to connect the proportion of REM and non-REM dreams with our mental wellbeing.
It could be a factor in depression.
PATRICK MCNAMARA: Normally, we fall asleep through non-REM sleep, but depressives, people with endogenous depressant depression or severe depression, they go right to REM, and then they stay in REM, and they spend too much time in REM.
So if REM sleep is associated with all this unpleasant emotion and you get too much REM, then you are going to have a lot of unpleasant emotion. We call that depression.
ROBERT STICKGOLD: My sense is that when we're asleep and when we're dreaming, we are actually conscious and figuring out what's important about what happened to us and how that relates to everything else that's happened to us in the past and figuring out what that means about our future.
MATT WILSON: And when you think about the challenge that animals, that we as humans and the brain in general faces, it is the unknown of the future. And in REM, we may have the opportunity to step into that future world with no risk, because the consequences are simply things don't work out as you might have expected, and then you wake up.
You can watch the 51 minute program on the PBS site or read the transcript.