"Women need not go into secrecy if they're struggling," said William Meyer, a clinical social worker and associate professor at Duke University Medical Center. "Women who suffer from depression do not, except in really extreme, exceptional cases, ever hurt their babies, ever put their babies in harm's way."
Authorities identified 34-year-old Miriam Carey of Stamford, Conn., as the woman who was shot to death by police Thursday after trying to drive through barricades at the White House with her 1-year-old in the car. Carey's mother told ABC News that her daughter suffered from postpartum depression and at one point was hospitalized. Friday, a federal law enforcement official said Carey also had delusions that the president was communicating with her and that her condition had been deteriorating over the past 10 months.
There are no details on Carey's official diagnosis or treatment.
But having delusions is not a symptom of the postpartum depression that affects anywhere from 10 percent to 20 percent of new mothers.
Most new mothers have a bit of the "baby blues," occasional feelings of sadness or anxiety soon after giving birth. Symptoms of postpartum depression are more serious and last longer, and they can require treatment ranging from support groups to medication.
Symptoms of postpartum depression include lacking interest in the baby; mood swings between sadness and irritability; fatigue and lack of energy; and withdrawal from family and other interests. In severe cases, a woman may have suicidal thoughts. According to the nonprofit Postpartum Health Alliance, women also may have "scary thoughts" of something bad happening to the baby.
"If it's just a case of postpartum depression, you usually don't see people hurting others or getting aggressive," stressed Dr. Ariela Frieder, a psychiatrist at New York's Montefiore Medical Center who specializes in post-pregnancy mood disorders.
In contrast, postpartum psychosis can come with hallucinations, paranoia, confused thinking and desires to hurt the child. It is very rare, occurring in about 1 in 1,000 women after childbirth, Frieder said.
It's an emergency that usually occurs within a few weeks of delivery, according to a 2011 review published in the Journal of Women's Health.
Nor does it tend to last for a year, noted Duke's Meyer.
Sometimes women who appear to have postpartum psychosis actually have a different mental illness — bipolar disorder — that may not be properly diagnosed unless symptoms occur again long after pregnancy, Frieder cautioned.
Whatever happened with the Connecticut woman, overall, postpartum depression is under-recognized, said Eileen Magri of Winthrop University Hospital on Long Island, N.Y.
Stigma discourages new mothers from seeking help, and families that do recognize a problem often have no idea where to turn, Magri said. She runs a special program that screens new mothers for signs of postpartum risk, such as a family history of mental illnesses, or the mother experiencing recent stressful events. Those considered at risk receive home visits from social workers who are on the lookout for developing symptoms.