So many new mothers experience some sadness and apprehension about the responsibility of caring for their babies that these feelings cannot be considered abnormal.

However, in some instances postpartum depression can develop, which can become a serious problem, according to a psychiatrist at New York University Medical Center."At least half of all new mothers experience some signs of postpartum blues a few days after delivery," said Helen DeRosis, M.D., associate clinical professor of psychiatry at the Medical Center.

"The feelings may be aggravated by a nonexistent or weakened support system," DeRosis observed. "The husband has to go back to work, other helpers and family members leave, and the woman is alone with an overwhelming and seemingly endless responsibility." Hormonal factors associated with childbirth may also affect mood.

An article in an issue of the New York University Medical Center Health Letter explains that the typical "baby blues" usually disappear within two weeks and need no treatment other than emotional support from spouse and family.

"If these feelings last longer than three weeks and are not resolved, a major depression may be developing," DeRosis maintained.

Some women experience no symptoms of depression in the first weeks after giving birth, but may become depressed after that. They may lose their appetite, have difficulty sleeping, and seem to have little interest in and derive no pleasure from their life.

"Postpartum depression may affect as many as 15 percent of new mothers and can last up to a year or more," she asserted. "Although it can happen to anyone, women who respond to other stresses by becoming depressed or anxious are more likely to be at higher risk."

Other risk factors include lack of support from partner, friends or family; conflicts between motherhood and career; and being a single mother.

A key factor in treatment is help with caring for the baby. Joining a new mothers' group may also be beneficial.

Some women may also require psychotherapy or antidepressant medication. In rare instances - one or two cases out of every 1,000 births - major depression may involve a psychosis.

"This is most likely to occur if a woman has a predisposition to mental illness, or previous episodes of severe depression," DeRosis noted. In severe cases, hospitalization may be necessary.

"These women may be irritable, fatigued and subject to mood swings immediately after the baby is born," DeRosis said. "A few go on to develop a thought disorder, and may lose their sense of reality. They may suffer from delusions, or think they hear voices."

The women in this group may be dangerous both to themselves and to their newborns. Treatment involves hospitalization, medication, and counseling for both mother and partner.