Are seasonality of mood and eveningness closely associated?

It has been suggested that being an "evening type" might enhance susceptibility to non-seasonal and seasonal affective disorders (SAD). In a survey and a prospective study, we examine the relationship between mood seasonality and circadian typology. In the survey study, the Morningness-Eveningness Questionnaire (MEQ) and the Seasonal Pattern Assessment Questionnaire (SPAQ) were administered to 1715 university students from Spain and Italy. In the prospective study, 18 subjects, selected from the Italian sample, self-assessed their mood monthly for over a year. A slight but significant negative correlation between the MEQ score and the Global Seasonality Score was found in the survey study, with a significantly higher incidence of evening versus morning types among the students with seasonal depression. These results were not replicated when the Spanish sample was analysed separately. In the prospective study, evening types did not present a higher annual range of mood variations than morning types. Caution should be exercised in ascribing eveningness as a risk factor in SAD since other underestimated factors, including social-cultural conditions, might be involved in the pathogenesis of mood seasonality.