Dreams are one of the most fascinating—and least understood—aspects of sleep. Though science has offered possibilities, we don’t yet understand the purpose of dreaming. Dreams can encompass a dramatic range of emotion, and subject matter. Some dreams seem plucked directly from our everyday lives. Most of us have had the experience of waking up shaking our heads at the odd and sometimes amusing circumstances that unfolded while dreaming. Dreams can contend with deep emotions, dealing with loss and reunion, anger, sorrow, and fear. Bad dreams and nightmares are among the most startling and emotionally potent of remembered dreams. Even a partially remembered disturbing dream can linger in our waking minds. But what do we know about this phenomenon of disturbed dreaming? And what’s the difference between a bad dream and a nightmare?
Much of the research into disturbed dreaming has focused on the neurological activity of these dreams, as a way to investigate the function and purpose of dreaming. Other research has focused on the connections between disturbed dreams and psychological conditions, such as post-traumatic stress disorder, and anxiety disorders. Less attention has been paid to the content of disturbed dreams, in particular the disturbing dreams that occur as a normal aspect of sleep life among a broad and varied population. We know that nightmares and bad dreams are common experiences—but we don’t know much about what these dreams contain.
What distinguishes a nightmare from a bad dream? One common theory is that nightmares are more emotionally disturbing and intense versions of bad dreams, a more severe form of the same essential phenomenon. One way nightmares are often distinguished from dreams is in whether the dream causes a person to wake—whether out of fear, or to put an end to the dream.
New research investigates the content of disturbed dreams, in an effort to gain a better understanding of what emotions, triggers, and themes propel these dreaming experiences, and also to help further illuminate potential distinctions between bad dreams and nightmares. Researchers at Quebec’s Université de Montréal recruited 572 volunteers, both men and women, to keep daily dream reports of all remembered dreams—good and bad—for anywhere from 2-5 consecutive weeks. The reports included details about dreams’ narratives, the emotions present and their level of intensity, as well as the presence of sleep terrors—brief, highly intense periods of fright during dreams, that are often accompanied by actual screaming or movement like sleepwalking. Researchers considered episodes of sleep terrors to be distinct from nightmares.
They collected nearly 10,000 dream reports on dreams of all types. From this collection, researchers identified 431 bad dreams and 253 nightmares, experienced by 331 participants, which met the criteria for evaluation. Researchers excluded dreams that were too vague to analyze, as well as dream experiences that seemed to be sleep terrors. They also excluded nightmares and bad dreams experienced by people who reported having only these 2 types of dreams. Researchers used the result of waking from the dream as the distinguishing characteristic between bad dreams and nightmares: nightmares resulted in awakenings, and bad dreams did not.
Researchers defined several themes for volunteers to use in identifying the content of their dreams. The themes covered common territory for disturbed dreams, including physical aggression, being chased, interpersonal conflicts, accidents, failures and helplessness, evil presences, disasters and calamities, apprehension, worry, and health concerns. Volunteers were allowed to identify both primary and secondary themes.
They also established emotional categories to further define dream content, including fear, anger, sadness, confusion, disgust, guilt, and frustration. Researchers used scales of both rationality and “everydayness” to evaluate levels of bizarreness in disturbed dreams.
Their results give insight into the complex emotional and thematic landscape of disturbing dreams, as well as new possibilities for delineation between bad dreams and nightmares:
- Nightmares occurred more rarely than bad dreams, according to results. Of a total of 9,796 dreams collected, nightmares made up 2.9%, while bad dreams accounted for 10.8% of all dreams.
- The most common themes in both bad dreams and nightmares were physical aggression, interpersonal conflicts and failure or helplessness. More than 80% of nightmares, and more than 70% of bad dreams contained one or more of these themes, compared to 38.2% of non-disturbing dreams.
- Fear was the most common emotion reported in both nightmares and bad dreams. Among nightmares, 65.1% contained fear as the main emotion, as did 45.2% of bad dreams.
- Fear was not only more common in nightmares, it also took a larger proportional share of emotional content in nightmares than in bad dreams.
- Though fear was the most prevalent emotion, nearly half of all disturbing dreams had primary emotions other than fear.
- Volunteers reported nightmares having significantly higher intensity than bad dreams.
- Nightmares contained more aggression, more frequent experiences of failure, as well as more unfortunate and negative conclusions, than bad dreams. Nightmares were also more bizarre.
- Physical aggression was 1.5 times more frequent in nightmares than in bad dreams. Evil presences and experiences of being chased were other commonly reported themes of nightmares.
- Bad dreams overall contained a wider range of themes than nightmares. After physical aggression, interpersonal conflicts, and failure, bad dreams also included themes related to health concerns and apprehension and worry.
- The thematic differences between nightmares and dreams suggested to researchers that nightmares are more likely to contain threats to basic physical security and survival, while bad dreams are more apt to grapple with a broader range of psychological anxieties.
- Researchers found some interesting differences between men’s and women’s dreams. Both men and women dreamed about the same basic range of thematic and emotional content. But men’s nightmares were more heavily populated with themes of disaster and calamity, while women’s nightmares were more than twice as likely to contain interpersonal conflicts.
One particularly unexpected finding? Researchers compared the presence of negative events and outcomes in everyday dreams to disturbing dreams. They found nightmares and bad dreams contained more aggressions and misfortunes, and contained fewer positive, friendly aspects than everyday dreams. However, bad dreams and nightmares contained less failure than everyday dreams. This suggests, says researchers, that our disturbing dreams deal less often with issues of competence than more ordinary, less overtly upsetting everyday dreams.
Fascinating stuff, isn’t it? These results give further credence to the theory that nightmares are a rarer, stranger, and more intense form of bad dreams, but that both types of disturbed dreaming are versions of the same basic experience. It’s not clear what purpose these dreams serve, or what relationship the content of our disturbing dreams may have to issues and concerns in our waking lives. But these findings should make scientists—and the rest of us—eager to discover more about our dreaming lives.
Michael J. Breus, PhD
The Sleep Doctor™