Purpose: The effects of breastfeeding on postpartum depression symptoms and stress using physiological measures require investigation. Background: Breastfeeding suppresses the secretion of cortisol. Oxytocin levels correlate negatively with symptoms of postpartum depression. Aim: To investigate the effects of breastfeeding on stress and postpartum depression. Methods: We examined 79 breastfeeding women using the Edinburgh Postnatal Depression Scale, the Perceived Stress Scale-10, and the Breastfeeding Self-Efficacy Scale, and measured the salivary cortisol levels before and after breastfeeding. Findings: There was a negative correlation between the duration of suckling and changes in salivary cortisol levels following breastfeeding (rs = −0.333, p < 0.05). Salivary cortisol levels immediately following breastfeeding were significantly lower compared to mothers who used mixed feeding methods (p < 0.001). Breastfeeding mothers had lower perceived stress than mothers using mixed feeding methods (β = −0.260, p < 0.05). There was no association between breastfeeding and postpartum depression; however, there was an association between postpartum depression and perceived stress (β = 0.622, p <0.001). Conclusion: Salivary cortisol levels significantly decreased following breastfeeding, with longer suckling times correlating with lower cortisol levels. Breastfeeding reduced stress and increased breastfeeding self-efficacy.
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