Your question doesn't appear to match the text you have with it. I do not know what specific article you are referring to however the research evidence overall indicates that lowest rates of PPD are found in women who are exclusively breastfeeding. This is due to the physiologically normal hormonal state postpartum that is designed to support nurturing and milk production. The hormone oxytocin is well-known as a relaxant and if the mother is not breastfeeding then her oxytocin level is lower that if breastfeeding. There is also the positive feelings of being able to nurture her child. If the mother is having difficulties with breastfeeding (physically or psychologically) or is inadequately supported and advised to not breastfeed, and adds a breast milk substitute given by bottle there is both the effect from experiencing the difficulties and the hormonal effects of reduced suckling. This stress can contribute to depression. Effective support during antenatal, labour and birth, and postnatal stages to start and to continue breastfeeding contributes to a mother more able to cope with mothering.

A study in Durban, South Africa by Kindra et al (2012) cited in my thesis (2017), has shown that fewer mothers who were exclusively breastfeeding had experienced depression than mothers who used formula feeding. Donaldson-Myles (2012) also found that exclusive breastfeeding increased the production of prolactin and oxytocin, which are reported to reduce the incidence of postnatal depression.

Hello,

Those who are only bottle-fed, and mothers who feed with breast and bottle, may actually want to feed completely from the breast, but have not been able to achieve this partially or at all. This situation may have caused them to develop thoughts that will affect their emotions negatively.