Postpartum depression and mother-offspring conflict over maternal investment

Annika Gunst; My Sundén; Riikka Korja; Amy M Boddy; Jennifer Kotler; E Juulia Paavonen; Henna-Maria Uusitupa; Linnea Karlsson; Hasse Karlsson; Jan Antfolk

doi:10.1093/emph/eoaa049

Postpartum depression and mother-offspring conflict over maternal investment

Evol Med Public Health. 2021 Jan 2;9(1):11-23. doi: 10.1093/emph/eoaa049. eCollection 2021.

Authors

Annika Gunst¹, My Sundén¹, Riikka Korja^{2

3}, Amy M Boddy⁴, Jennifer Kotler^{5

6}, E Juulia Paavonen^{7

8}, Henna-Maria Uusitupa³, Linnea Karlsson^{3

9

10}, Hasse Karlsson^{3

10}, Jan Antfolk¹

Affiliations

¹ Department of Psychology, Åbo Akademi University, Tehtaankatu 2, Turku 20500, Finland.
² Department of Psychology, University of Turku, Assistentinkatu 7, Turku 20014, Finland.
³ Department of Clinical Medicine, FinnBrain Birth Cohort Study, Turku Brain and Mind Center, University of Turku, Lemminkäisenkatu 3, Turku 20014, Finland.
⁴ Department of Anthropology, University of California, Santa Barbara, CA 93106 3210, USA.
⁵ Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
⁶ Department of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138, USA.
⁷ Department of Public Health Solutions, Finnish Institute for Health and Welfare, P.O. Box 30, 00271 Helsinki, Finland.
⁸ Centre for Population Health Research, Turku University Hospital and University of Turku, Kiinamyllynkatu 10, Turku 20520, Finland.
⁹ Pediatric Research Center, Helsinki University Hospital, P.O. Box 63, 00014 Helsinki, Finland.
¹⁰ Department of Psychiatry, Turku University Hospital and University of Turku, Lemminkäisenkatu 3, Turku 20014, Finland.

Abstract

Background and objectives: As the mother-offspring relationship is central to human reproduction, postpartum depression symptoms are difficult to explain in evolutionary terms. We proposed that postpartum depression might arise as a 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 6 months postpartum from 1598 Finnish mothers. We hypothesized that infant night waking at 6 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 moderately associated with postpartum depression symptoms, and this association was mediated by maternal sleep disturbance (R ²=0.09). Contrary to our prediction, we found that increased breastfeeding was associated with less postpartum depression symptoms.

Conclusions and implications: We conclude that postpartum depression symptoms might partly 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 can potentially improve our understanding of the involved behavioral processes of both mother and offspring, and allow interventions designed to benefit the well-being of both parties. Lay Summary: We proposed that postpartum depression is due to an evolutionary conflict between mother and infant, where the infant tires the mother to delay the arrival of a sibling. We found a link between infant night waking and postpartum depression, mediated by the mother's sleep, but not by breastfeeding frequency.

Keywords: breastfeeding; fatigue; infant night waking; maternal sleep; mother–offspring conflict; postpartum depression.