Longitudinal Trajectories of Postpartum Depression and Their Biological and Psychosocial Determinants in South East Nigerian Women: A Prospective Cohort Study

Postpartum depression (PPD) is not a uniform clinical entity but encompasses heterogeneous trajectories of symptom onset, persistence, and resolution, yet longitudinal trajectory analysis with biological correlate characterisation has not been conducted in any sub-Saharan African population. This dissertation examines longitudinal PPD trajectories and their biological and psychosocial determinants in South East Nigerian women. A prospective cohort of 300 women recruited at first-trimester antenatal booking at Nnamdi Azikiwe University Teaching Hospital (Anambra) and Federal Medical Centre Owerri (Imo) was followed at 6 weeks, 3 months, 6 months, and 12 months postpartum. Edinburgh Postnatal Depression Scale scores were collected at each time point alongside serum cortisol, inflammatory cytokines (IL-6, TNF-alpha, CRP), and psychosocial measures (social support, intimate partner violence, economic hardship). Group-based trajectory modelling identified four distinct PPD trajectory classes: resilient (42 percent), transient (28 percent), persistent moderate (19 percent), and chronic severe (11 percent). Baseline inflammatory cytokine elevation was a significant biological predictor of chronic severe trajectory membership (OR 4.7). IPV during pregnancy (OR 5.2) and social support deficit (OR 3.9) predicted chronic trajectory independently of biological factors. The chronic severe group had significantly poorer mother-infant bonding and infant developmental outcomes at 12 months. The dissertation introduces the Biopsychosocial Trajectory Model of PPD (BTM-PPD) and provides a theoretical and empirical foundation for trajectory-informed prevention and treatment of PPD in South East Nigerian women. Keywords: postpartum depression, longitudinal trajectory, biopsychosocial, South East Nigeria, inflammatory markers