Pretty much exactly what you’d expect.
Few studies have delved into the dark details and emotions associated with nightmares, and even fewer have used dream logs as a basis for analysis.
As researchers at the University of Montreal note in a new study forthcoming in Sleep, daily logs are the so-called “gold standard” for this type of research because other evaluations, like interviews and questionnaires, can “yield inaccurate dream reports due to the fragile nature of dreams’ long-term recall as well as memory and saliency biases.”
When scientists ask a subject to recount the details of a nightmare, they’re more inclined to draw from the extreme fringes than the standard fare. “This may explain why themes of falling and of being chased are among the most frequently reported themes in studies based on questionnaire or interview data while appearing much less frequently in prospective logs,” the researchers write.
In this particular study, the psychologists asked 572 participants to record their dreams for two to five weeks. They were also asked to reflect on their emotions at the time of recording. After an analysis of “9,796 dream reports,” they whittled down the results to “253 nightmares and 431 bad dreams reported by 331 participants.” The researchers defined nightmares as dreams unpleasant enough to pull the participants out of sleep. Bad dreams were terrible, but did not cause the subjects to stir.
For the rest of the story: http://www.psmag.com/navigation/health-and-behavior/whats-difference-nightmare-bad-dream-73506/