CHICAGO: New moms face increased risks for a variety of mental problems, not just postpartum depression, according to one of the largest studies of psychiatric illness after childbirth.

New dads aren't as vulnerable, probably because they don't experience the same physical and social changes associated with having a baby, the researchers and other experts said.

The study, based on medical records of 2.3 million people over a 30-year period in Denmark, found that the first three months after women have their first baby is riskiest, especially the first few weeks. That's when the tremendous responsibility of caring for a newborn hits home.

During the first 10 to 19 days, new mothers were seven times more likely to be hospitalised with some form of mental illness than women with older infants.

Compared to women with no children, new mothers were four times more likely to be hospitalised with mental problems.

New mothers also were more likely than other women to get outpatient psychiatric treatment.

However, new fathers did not have a higher risk of mental problems when compared with fathers of older infants and men without children. The prevalence of mental disorders was about 1 per 1,000 births for women and just 0.37 per 1,000 births for men.

Mental problems included postpartum depression, but also bipolar disorder, with altering periods of depression and mania; schizophrenia and similar disorders; and adjustment disorders, which can include debilitating anxiety.

The study underscores a need for psychiatric screening of all new mothers and treatment for those affected, according to an editorial accompanying the study in Wednesday's Journal of the American Medical Association.

"Mental health is crucial to a mother's capacity to function optimally, enjoy relationships, prepare for the infant's birth, and cope with the stresses and appreciate the joys of parenthood,"the editorial says.

Two of the editorial's three authors reported financial ties to the psychiatric drug industry. The study researchers said they had no financial ties to the industry.

They examined national data on Danish residents from around 1973 to July 2005. About 1.1 million participants became parents during the study.

A total of 1,171 mothers and 658 fathers - none diagnosed with any previous mental problems - were hospitalised with a mental disorder after childbirth.