Pregnant women having lower levels of an anti-anxiety hormone in their second trimester had an increased chance of developing postpartum depression a study has shown. Postpartum depression -- depression that occurs after childbirth -- affects early bonding between the mother and child. According to the study appearing in the journal Psychoneuroendocrinology a woman with an allopregnanolone hormone level of about 3.75 nanograms per milli-liter had a 33 per cent likelihood of developing the disorder. While a woman having 7.5 nanograms per milli-liter had a 1.5 per cent chance of developing postpartum depression. For every additional nanogram per milli-liter increase in