Seasonal aspects of peripartum depressive symptoms

Sammanfattning: Every year, a large proportion of pregnant and newly delivered women develop peripartum depression, a condition that may cause long-term suffering for the entire family. Although there is a lack of consensus, some studies propose an association between season and the risk of developing depression during pregnancy and the postpartum period. Furthermore, the immune system, which undergoes numerous structural changes during pregnancy, has been suggested to exhibit seasonal variations. In addition, discrepancies in metabolic profiles have been reported between women with and without depression after childbirth. This thesis aimed to investigate seasonal aspects of peripartum depressive symptoms (PPDS) and biological markers during the peripartum period. The data mainly derived from the prospective population-based Biology, Affect, Stress, Imaging, and Cognition (BASIC) study, but data were also included from the longitudinal population-based Uppsala-Athens (UPPSAT) study. The presence of depressive symptoms was primarily assessed using the Edinburgh Postnatal Depression Scale (EPDS). There were no consistent associations between season, meteorological parameters, air pollen count, and PPDS. Moreover, a number of inflammatory markers were identified as having seasonal variations among samples from pregnant women. On the contrary, only one marker had a seasonal pattern during the early postpartum period. Furthermore, metabolic profiles were not discriminatory between pregnant women with and without depressive symptoms. However, when divided into summer and winter childbirths, discrepancies were identified in metabolic profiles between summer cases and controls, as well as between summer and winter controls. In summary, the studies included in this thesis suggest that season, specifically, is not associated with PPDS. However, season may have a moderating effect on the association between depressive symptoms and the metabolic profile of pregnant women. In addition, the seasonal variations appears more prominent among inflammatory markers during late pregnancy, compared with the early postpartum period. These findings suggest that women need equal attention in clinical care regardless of the season during which they give birth. Future studies on biological aspects of PPDS and immune-associated conditions are encouraged to also assess seasonality.