OBJECTIVE We aimed to investigate the moderating effect of age on the association of morningness-eveningness with depression in subjects with a broad range of ages. The hypothesis of the current study was that there would be a relationship between depressive symptoms and eveningness, especially in young age groups. METHODS Three hundred sixty-one subjects (male/female=140/221) from 19 to 79 years of age participated in the study. Subjects were separated into five age groups: (1) < or = 20s (n=70), (2) 30s (n=85), (3) 40s (n=97), (4) 50s (n=54) and 5) > or = 60s (n=55). The Horne-Osteberg Morningness-Eveningness Questionnaire (MEQ) and the Center for Epidemiological Studies for Depression Scale (CES-D) were administered to all subjects. RESULTS MEQ showed a significantly independent and negative association with CES-D (beta=-.27, P<.001), which meant the association between eveningness and depressive symptoms. The negative association between MEQ and CES-D were significant in < or = 20s (beta=-.31, P=.01), 50s (beta=-.38, P<.01) and > or = 60s (beta=-.35, P<.01), while there was no significant association between MEQ and CES-D in 30s (beta=-.06, P=.56) and 40s (beta=-.10, P=.32). CONCLUSIONS Our findings demonstrate an association of depressive symptoms with eveningness, which was more prominent in younger or older aged than in middle aged. Our findings suggest that the association between depressive symptoms and eveningness might be moderated by age.