Baseline Chronotype as an Independent Predictor of 12-Week Escitalopram Response in First-Episode Major Depressive Disorder: A Prospective Cohort Study

Introduction: Chronotype is associated with depression risk and symptom severity, but its ability to predict antidepressant response remains uncertain, and prospective Indian data are limited. The presents study examined whether baseline chronotype independently predicted 12-week improvement in first episode major depressive disorder (MDD) after accounting for sleep quality and clinical severity. Materials and Methods: In this prospective-cohort study, 100 antidepressant naive adults with first episode nonpsychotic MDD received escitalopram for 12 weeks. Chronotype was assessed using the 19 item Morningness-Eveningness Questionnaire (MEQ), sleep using the Pittsburgh Sleep Quality Index (PSQI), and depression using the Montgomery–Asberg Depression Rating Scale (MADRS) at baseline and weeks 2, 6 and 12. The primary outcome was percentage reduction in MADRS at week 12. Response was defined as ≥50% reduction and remission as MADRS ≤10. Hierarchical regression tested the incremental contribution of baseline MEQ beyond age, sex, episode duration, baseline MADRS and PSQI. Results: Evening, intermediate and morning chronotypes comprised 23, 51 and 26 patients, respectively. Mean MADRS reduction was 51.6±11.7%, 59.1±11.9% and 62.7±11.9% across these groups (p=0.005). Response occurred in 47.8%, 76.5% and 92.3% (p=0.002), whereas remission showed a nonsignificant gradient (17.4%, 33.3%, 42.3%; p=0.168). After adjustment, each 10-point higher MEQ score predicted 3.2 percentage-points greater MADRS reduction (p=0.011); adding MEQ increased model R² by 0.062 (p=0.011). Conclusion: Greater morningness was independently associated with greater symptomatic improvement and higher likelihood of antidepressant response, even after accounting for baseline sleep quality.