"Counterintuitively, not getting enough sleep can lead to more intense dreaming. A 2005 study found that when subjects didn’t get enough REM sleep one night, their brains tried to make up for it the next, by engaging in longer periods of REM. Sleep for sleep-deprived people also tends to be more extreme; neurologist Mark Mahowald of the University of Minnesota told Scientific American, “When someone is sleep deprived we see greater sleep intensity, meaning greater brain activity during sleep; dreaming is definitely increased and likely more vivid.” Scientific American terms this effect “REM rebound,” and it can occur in a variety of situations."