For decades people have been worrying about whether nightmares affect the quality of sleep that we get. For most people, though, we can be fairly sure that all dreams – even nightmares – are beneficial to the restorative function that has sleep. When we sleep, we pass through several stages: light sleep, deep sleep and finally REM sleep. Each one of these stages is important, but the most important when it comes to helping the body recover is deep sleep. During deep sleep, the body relaxes and temperature drops. It’s also a period where dreams do not take place.
So if the most beneficial part of sleep is deep sleep, where dreams don’t take place, what is the actual benefit of dreams? According to Isabelle Arnulf, a neurologist and director of sleep pathology at Pitie-Salpetriere hospital, of thousands of dreams that have been studied during scientific experiments, bad dreams “prepare us for the danger in this safe place that is the dream to allow us to face it better in real life.” Interestingly, of all the dreams analyzed, 82% were violent or negative. One could make the argument that if the majority of dreams are nightmares, then they must have some evolutionary use – else it would be bizarre for them to be so frequent.
One other recent area of research by Antonion Zadra, however, distinguishes between just “bad” dreams and “nightmares” that are so disturbing that they wake us up. Nightmares that happen regularly can actually be harmful, Zadra argues – they can reduce the amount and quality of sleep, and recurring nightmares can be related to depression, anxiety and neuroticism.