Gender differences in diurnal variations of subjective activation and mood

This article evaluates the influence of gender on diurnal and postlunch period variations in subjective activation and mood. This topic is not often addressed in the literature; particularly, little attention has been paid to how biological rhythms might bias research results. We studied 40 university student volunteers (20 men, 20 women) aged 18 to 23 years old (X = 20.23, SD = 1.03); they responded to questions on eight unipolar visual analog scales every hour from 08:00 to 21:00. Gender differences were observed in both diurnal and postlunch variations for scales of positive activation (alertness, vigor); sleepiness, however, was only sensitive to diurnal variation, and weariness was sensitive only to a postlunch effect. Women displayed a morning-type pattern, with their optimal moment (11:00) coming 2h earlier than for men, and their activation ratings ranged more widely. The only mood scale that showed differences related to gender was that of happiness, for which women had a higher diurnal mean, a diurnal peak 2h earlier, and a less-intense postlunch effect. Endogenous control of rhythmic pattern appears to be less intense in women, probably due to the coexistence of circamensual rhythmicity, although environmental or sociocultural influences may play a modulating role. Chronopsychological gender differences in affective states should be studied further given the implication they have for the prevention and treatment of mood disorders.