'I didn't know it was possible to feel that tired': Exploring the complex bidirectional associations between maternal depressive symptoms and fatigue in a prospective pregnancy cohort study

Depressive and fatigue symptoms are common health concerns for women in the postnatal period. Few studies have sought to investigate the role of fatigue in the development and maintenance of depressive symptoms. The aim of this paper was to examine the relationship between depressive symptoms and fatigue over the course of the first 4 years postpartum, in particular focusing on the extent to which fatigue at earlier time points predicted later depressive symptoms and vice versa. Data from over 1000 women participating in a longitudinal study of Australian women's physical and psychological health and recovery after childbirth were used. An autoregressive cross-lagged panel model was tested to assess the mutual influences of fatigue and depressive symptoms across five time points at 3, 6, 12 and 18 months postpartum, and at 4 years postpartum. A complex bidirectional relationship between fatigue and depressive symptoms from 3 months to 4 years postpartum was observed, where fatigue at earlier time points predicted depressive symptoms at later time points, and vice versa. The findings of this study suggest interventions targeting the prevention and management of fatigue may also confer some benefit in improving or preventing the development of depression symptoms in the early parenting period.