Postpartum Depression and Mother-offspring Conflict over Maternal Investment

Abstract

Background and objectives: As the mother-offspring relationship is central to human reproduction, the high incidence of postpartum depression symptoms is difficult to explain in evolutionary terms. We proposed that postpartum depression might be the adverse result of evolutionary mother-offspring conflict over maternal investment, and investigated the association between postpartum depression symptoms, infant night waking, maternal sleep disturbance and breastfeeding frequency. Methodology: We conducted a cross-sectional analysis using survey responses at six months postpartum from 1598 Finnish mothers. We hypothesized that infant night waking at six months postpartum would be associated with postpartum depression symptoms, and that this association would be mediated by maternal sleep disturbance and a higher breastfeeding frequency.Results: Infant night waking was associated with postpartum depression symptoms, and this association was mediated by maternal sleep disturbance. Contrary to expectations, we found that the increased breastfeeding was associated with less postpartum depression symptoms. Conclusions and implications: We conclude that postpartum depression symptoms might be the result of increased maternal fatigue stemming from high offspring demands on maternal investment, but that this is not due to the metabolic strain from increased breastfeeding. Studying postpartum depression from the mother-offspring conflict perspective improves our understanding of the involved behavioral processes of both mother and offspring, and thus allows interventions designed to improve the well-being of both parties.