RESUMEN
Postpartum depression (PPD) is the most important postpartum mood disorder due to its significant effect on both the infant and family health. Arginine vasopressin (AVP) has been suggested as a hormonal agent involved in the development of depression. The purpose of this study was to investigate the relationship between the plasma concentrations of AVP and the score of Edinburgh Postnatal Depression Scale (EPDS). This cross-sectional study was conducted in 2016-2017 in Darehshahr Township, Ilam Province, Iran. In the first phase, 303 pregnant women, who were at 38 weeks, met the inclusion criteria, and were not depressed (according to their EPDS scores) were included in the study. In the 6-8 week postpartum follow-up, using the EPDS, 31 depressed individuals were diagnosed and referred to a psychiatrist for confirmation. The maternal venous blood samples of 24 depressed individuals still meeting the inclusion criteria and 66 randomly selected non-depressed subjects were obtained to measure their AVP plasma concentrations with ELISA assay. There was a significant positive relationship between plasma AVP levels and the EPDS score (P = 0.000, r = 0.658). Also the mean plasma concentration of AVP was significantly higher in the depressed group (41.35 ± 13.75 ng/ml) than in the non-depressed group (26.01 ± 7.83 ng/ml) (P < 0.001). In a multiple logistic regression model for various parameters, increased vasopressin levels were associated with increased odds of PPD (OR = 1.15, 95% CI = 1.07-1.24, P = 0.000). Furthermore, multiparity (OR = 5.45, 95% CI = 1.21-24.43, P = 0.027) and non-exclusive breastfeeding (OR = 13.06, 95% CI = 1.36-125, P = 0.026) were associated with increased odds of PPD. Maternal gender preference (having a baby of desired and desired sex) decreased the odds of PPD (OR = 0.13, 95% CI = 0.02-0.79, P = 0.027 and OR = 0.08, 95% CI = 0.01-0.5, P = 0.007). AVP seems to be a contributor to clinical PPD by affecting the hypothalamic-pituitary-adrenal (HPA) axis activity. Furthermore, primiparous women had significantly lower EPDS scores.