Gender differences in morningness-eveningness assessed by self-report questionnaires: A meta-analysis

Gender differences in circadian typology and in biological rhythms have been revealed by using biological measurements but results based on self-report questionnaires are inconclusive. I applied meta-analytical tools to examine gender differences in morningness. I searched different databases for studies presenting values for morningness in males and females. Fifty-two studies were identified from which I I used the composite scale of morningness CSM, 29 the morningness-eveningness-questionnaire MEQ, and eight the morning/evening questionnaire M/E. Most studies (51.9%) were carried out with students. There was no significant publication bias. Taken together, the meta-analysis suggests a weak but significant effect of gender on morningness (overall effect size E = 0.097 under a fixed effects model and E = 0.0845 under a random effects model). Girls and women were significantly more morning oriented than boys and men. Further, standard deviations of mean age of the subjects had a significant effect on effect sizes suggesting that large standard deviations, and thus a large age range within a study, produced smaller effect sizes. Focusing on student samples revealed higher effect sizes (E = 0.196). With regard to the different questionnaires, the CSM produced the largest effect sizes, followed by the MEQ. (c) 2007 Elsevier Ltd. All rights reserved.