Impact of chronotype on depression: The mediating roles of rumination and perceived stress.

Chronotype represents an independent risk factor for depression, yet the psychological mechanisms underlying this association remain unclear. Potential mediators may include social jetlag (SJL), sleep quality, rumination, and perceived stress. Thus, this China-based study enrolled 122 patients with Depressive Episode (DE) and 126 healthy Controls (HC), assessing participants using: the Beck Depression Inventory (BDI), Morningness-Eveningness Questionnaire (MEQ), Munich Chronotype Questionnaire (MCTQ), Pittsburgh Sleep Quality Index (PSQI), Ruminative Response Scale (RRS), and Perceived Stress Scale (PSS). Partial Spearman correlations examined relationships between BDI scores, chronotype, sleep quality, rumination, and perceived stress within each group. Mediation analyses employed MEQ scores as the independent variable and diagnostic status (DE vs HC) as the dependent variable, with moderated mediation analyses assessing age, sex, and work status influences. Results revealed significant indirect effects of chronotype on depression status through: sleep quality, symptom rumination, brooding, reflective pondering, PSS scores, perceived helplessness, and perceived self-efficacy. These mediating effects were moderated by sex or work status, but not age. The demonstrated association between evening chronotype and increased depression risk suggests that clinical interventions targeting sleep improvement, rumination reduction, and stress coping enhancement may be particularly beneficial for such individuals experiencing depressive symptoms.