The cause of 'postpartum blues' is:

Puerperal Blues/3 Days Blues/Baby Blues It is transient state of mental illness observed 4–5 days after delivery in nearly 50% of postpartum women. Postpartum blues occurs at the height of hormonal changes.  Patients present with depression, anxiety, fearfulness, insomnia, helplessness and negative feelings towards infant. It may last from a few days to 2–3 weeks. Generally self limited, 20% of women may develop depression in the first postpartum year. Treatment: Reassurance and psychological support of family members. Post-partum Depression It is observed in 10-20% of mothers. It is more gradual in onset over the first 4-6 months following delivery or abortion. Changes in hypothalamo-pituitary-adrenal axis may be a cause. Manifested by loss of energy and appetite, insomnia, social withdrawal, irritability and even suicidal attitude. Risk of recurrence 50-100% in subsequent pregnancies. Treatment: Should be started early. Fluoxetine or paroxetine is effective and has fewer side effects. According to kaplan, the cause of postpartum blues is : “The sudden decrease in estrogen and progesterone immediately after delivery may also contribute to the disorder, but treatment with these hormones are not effective.”