Gender differences in nightmare frequency: a meta-analysis.

Women tend to report nightmares more often than men, but this gender difference does not appear in children or older persons. A meta-analysis of 111 independent studies found that the difference emerges in adolescence, narrows with increasing age, and is influenced by how nightmare frequency is measured—studies using binary (yes/no) items show a smaller difference than those using rating scales. The definition of nightmare did not affect the gender gap. For children, the most influential factor was whether the data came from children's self-reports or parent reports. Candidate explanations such as dream recall frequency, depression, childhood trauma, and insomnia remain unexamined in systematic research on this gender difference.

Study at a glance

Abstract

Many studies have reported gender differences in nightmare frequency. In order to study this difference systematically, data from 111 independent studies have been included in the meta-analysis reported here. Overall, estimated effect sizes regarding the gender difference in nightmare frequency differed significantly from zero in three age groups of healthy persons (adolescents, young adults, and middle-aged adults), whereas for children and older persons no substantial gender difference in nightmare frequency could be demonstrated. There are several candidate variables like dream recall frequency, depression, childhood trauma, and insomnia which might explain this gender difference because these variables are related to nightmare frequency and show stable gender differences themselves. Systematic research studying the effect of these variables on the gender difference in nightmare frequency, though, is still lacking. In the present study it was found that women tend to report nightmares more often than men but this gender difference was not found in children and older persons. Starting with adolescence, the gender difference narrowed with increasing age. In addition, studies with binary coded items showed a markedly smaller effect size for the gender difference in nightmare frequency compared to the studies using multiple categories in a rating scale. How nightmares were defined did not affect the gender difference. In the analyses of all studies and also in the analysis for the children alone the data source (children vs. parents) turned out to be the most influential variable on the gender difference (reporting, age). Other results are also presented. Investigating factors explaining the gender difference in nightmare frequency might be helpful in deepening the understanding regarding nightmare etiology and possibly gender differences in other mental disorders like depression or posttraumatic stress disorder.