This is the first large-scale study that shows a link between childbirth and mental illness. "[The researchers] focus on severe psychiatric illness which really hasn't been done before, [and] is really important," said Dominguez.
Doctors -- and not just doctors who deliver babies -- feel this is a landmark study because it brings attention to an important public health need that is rarely mentioned. "The significance for this study in the medical community is that recognition is key to addressing this public health problem," said Dr. Dorothy Sit, assistant professor of psychiatry at the University of Pittsburgh School of Medicine.
"Often [postpartum mental illness] is not discussed," said Dominguez, because of the stigma surrounding mental illness. "Sometimes women are told to grin and bear it.
"I think there is a concept of superwomen, and some of the patients don't believe [mental illness] could happen to them."
Doctors hope this report will help new moms -- who do suffer symptoms of mental illness -- to speak up and get help.
"I think there is always need for getting the public to realize that psychiatric illness can happen to anyone, even when they're 'doing everything right' and even when potentially joyful events are happening," said Dr. Christine Barney, a private practice psychiatrist in White River Junction, Vt.
This public awareness could ultimately be better for baby. If mommy's mental illness is diagnosed early, it could protect baby from potential harm.
"[Mental illness in mom] can negatively impact a newborn's mental and motor development, and is associated with low self-esteem and behavior problems," said Sit.
The study illustratrates the reality that the sexes are not equally vulnerable when it comes to mental illness. Mental illness seems to hit first-time moms harder than it hits first-time dads, but experts can't say why that is.
It could be because of a woman's hormones, experts suggest, or it could have more to do with the pressure of being a parent.
"It may not only be hormones but also expectations of being a new mom" that make women more susceptible to mental illness, said Dominguez.
Perhaps the pressure of new motherhood brings out a mental illness that otherwise would have lay dormant, experts said.
"These women could have an underlying but unrecognized disorder that becomes apparent in the postpartum," said Sit.
These underlying psychiatric illnesses may be "more likely to become manifest when a woman is stressed, scared, socially isolated, fatigued and sleep-deprived," as with a new baby, said Barney.
The findings suggest that mothers are more involved in raising children than men, and that this change in lifestyle is what causes more mental illness in women than men after childbirth, according to study author Trine Munk-Olsen at the National Center for Register-Based Research in Aarhus, Denmark.
Munk-Olsen and her colleagues also said that men may be more vulnerable to mental illness than the data lets on, because men may seek medical help for psychiatric illness less often than women do.
It's hoped that this study will not only educate physicians to look for earlier warning signs of depression but will also educate new moms and dads to look for the signs of depression.