Although fear is the most frequently reported emotion in nightmares and bad dreams, almost half of all disturbing dreams contained primary emotions other than fear. These can include anger, sadness, and frustration. Also, we’ve published several studies showing that nightmares with these kinds of emotions are rated as being just as intense and disturbing as fear-driven nightmares. This is why the American Academy of Sleep Medicine defines nightmares as disturbing mental experiences rather than frightening dreams.