Relationship between depressive mood and chronotype in healthy subjects.

Aim: The endogenous circadian clock generates daily variations of physiological and behavior functions such as the endogenous interindividual component (morningness/eveningness preferences). Also, mood disorders are associated with a breakdown in the organization of ultradian rhythm. Therefore, the purpose of the present study was to assessed the association between chronotype and the level of depressive symptoms in a healthy sample population. Furthermore, the components of the depression scale that best discriminate the chronotypes were determined.

Methods: This cross-sectional study involved 200 volunteers, aged 18-99 years, 118 women and 82 men. The instruments were the Montgomery-Asberg Depression Rating Scale (MADRS), the Morningness/Eveningness Questionnaire, the Self-Reporting Questionnaire-20, and the future self-perception questionnaire.

Results: Logistic regression showed that subjects with the eveningness chronotype had a higher chance of reporting more severe depressive symptoms compared to morning- and intermediate-chronotypes, with an odds ratio (OR) of 2.83 and 5.01, respectively. Other independent cofactors associated with a higher level of depressive symptoms were female gender (OR, 3.36), minor psychiatric disorders (OR, 3.70) and low future self-perception (OR, 3.11). Younger age, however, was associated with a lower level of depressive symptoms (OR, 0.97). The questions in the MADRS that presented higher discriminate coefficients among chronotypes were those related to sadness, inner tension, sleep reduction and pessimism.

Conclusion: Identification of an association between evening typology and depressive symptoms in healthy samples may be useful in further investigation of circadian typology and the course of depressive disease.