A study suggests that vaginal delivery might lead to a better postnatal quality of life than cesarean delivery, especially with regards to physical health. Significant differences were found for vitality, mental health and physical functioning ... The findings indicate that in the short term, vaginal delivery might be preventive of postnatal depression.
I'm not surprised by these findings. Caesarean is major surgery; having a major operation and then having to care for a new baby must be a very stressful experience. Other research has shoen that operative births are more likely to leave a woman traumatised following her birth. Continuity of midwifery care is known to reduce the need for caesarean.