Although many new mothers are euphoric after delivering a child, some suffer mild to severe depression. Recent studies assign postnatal depression three classifications: the maternal blues, postnatal depression or postpartum neurotic depression, and postpartum psychosis. The maternal blues is a sadness lasting between a few hours to a few days. Postnatal depression or postpartum neurotic depression, a more disabling condition, is marked by mood swings, interrupted sleep and hostility. Postpartum psychosis, the most severe condition, is marked by the loss of realistic thinking in which a mother may suffer paranoia, nightmares, hallucinations and thoughts of harming herself or her baby.
One of the causes may be a large influx of hormones in the mother's body on the 4th or 5th day after labour.