Eveningness is associated with more severe depressive symptoms independently of sleep quality and fatigue level only in first-episode but not recurrent depression in major depressive disorder

People with an evening chronotype have an increased risk of experiencing a major depressive disorder (MDD). It is unclear if this effect is predominantly related to the initial development of MDD or also present in recurrent episodes. The current study aimed to investigate if the association between chronotype and depressive severity in MDD patients is comparable in MDD patients with first and recurrent episodes. 386 MDD patients, 70.7% females and aged between 16 and 64, participated in the study. The Morningness - Eveningness Questionnaire (MEQ), Pittsburgh Sleep Quality Index (PSQI), Multidimensional Fatigue Inventory (MFI20), and Quick Inventory of Depressive Symptomatology (QIDS-SR16) were administered to participants to determine chronotype, sleep quality, fatigue level, and depressive severity, respectively. Multivariate regression models were utilized to analyze how chronotype influences depressive severity. The study showed that chronotype, sleep quality, and fatigue level were all associated with depressive severity. Eveningness significantly predicted an increase in depressive severity independently of sleep quality and fatigue level only in patients with the first episode (-0.068, p = 0.010), but not in patients with recurrent episodes (0.013, p = 0.594). Circadian-focused treatment should be considered in first-episode depression only.