A study in the Dec.1 issue of the journal Sleep shows that dream-enacting behaviors are common in healthy young adults, and the prevalence of specific behaviors differs between men and women.
Results indicate that 98 percent of subjects (486/495) reported experiencing one of seven subtypes of dream-enacting behavior at least "rarely" in the last year. The most prevalent behavior subtype was "fear," with 93 percent reporting that they had felt signs of fear in their body after awakening from a frightening dream. Seventy-eight percent reported that they had awakened from an erotic dream to find that they were sexually aroused; 72 percent had awakened from a happy dream to find that they were actually smiling or laughing. Each of the other four behavior subtypes was reported by more than 50 percent of participants: They awakened from a dream to find that they were talking, crying, acting out an angry or defensive behavior such as punching or kicking, or acting out other movements such as waving or pointing. Women reported more speaking, crying, fear and smiling/laughing than men, and men reported more sexual arousal.
Lead author and co-investigator Tore Nielsen, PhD, professor of psychiatry at the Universit- de Montreal in Canada, was surprised by the high prevalence of dream-enacting behavior. Nielsen noted that more studies will need to be conducted to create a distinction between normal dream-enacting behavior and actions that are associated with REM sleep behavior disorder (RBD), which is characterized by abnormal behaviors emerging during rapid eye movement (REM) sleep that cause injury or sleep disruption.
"Normal episodes are usually extremely mild, for example, briefly jerking an arm or leg while waking up from a nightmare, once or twice a year," said Nielsen. "This is far different from RBD cases, which are typically very intense, and might involve repeatedly flailing an arm or a leg or smashing into something in the middle of a dream, not waking up easily from it, with occurrences several times a month."
A total of 1,140 first-year undergraduate students who were enrolled in introductory psychology courses voluntarily participated in the study. Approximately two-thirds were female. Participants completed several questionnaires concerning personality and dreaming.
To determine the type of questions that are best for eliciting reports of dream-enacting behavior, students were divided into three groups. Group one (mean age 19.9 years) was provided with general questions concerning dream-enacting behaviors, group two (mean age 20.1 years) received the same questions with examples, and group three (mean age 19.1 years) received questions describing specific behavior subtypes. The prevalence of dream-enacting behavior increased with increasing question specificity (35.9 percent in group one, 76.7 percent in group two and 98.2 percent in group three). According to the authors, these findings suggest that dream-enacting behaviors are common in the general population but are difficult for subjects to identify if detailed descriptions of the behaviors are not given.
The study distinguished the dream-enacting behavior of speaking out loud some of the words of a dream about talking from somniloquy (sleep talking), which was defined as speaking or making sounds during sleep without clear recall of an accompanying dream. Acting out the movements of a dream was distinguished from somnambulism (sleepwalking), which was defined as moving or walking during sleep without clear recall of a dream. Almost 61 percent of subjects in group three reported experiencing somniloquy at least "rarely" in the last year, and 40.9 percent reported somnambulism.
The authors speculate that there is a possibility of a personality trait involvement and a genetically determined predisposition for frequent dream-enacting behaviors. It remains unknown whether the dream-enacting behaviors of healthy subjects may predict future RBD symptoms.