Miriam Carey, the woman shot and killed by authorities near the Capitol building after she allegedly tried to ram a White House barrier, reportedly suffered from postpartum depression after giving birth to her daughter, the now 1-year-old who was in the car at the time of the incident.

Carey’s case of postpartum depression was so severe that she had to be hospitalized for the psychological condition, her mother, Idella Carey, told ABC News. Miriam Carey, 34, of Stamford, Conn., gave birth to daughter Erica in August 2012, as soon after started having symptoms of postpartum depression.

“She had postpartum depression after having the baby," Idella said. "A few months later, she got sick. She was depressed. ... She was hospitalized."

What is postpartum depression? While many pregnant women may feel a little down up to two weeks after giving birth, with symptoms ranging from mood swings to irritability to crying spells, postpartum depression is much more serious and lasts longer, according to WebMD.

Postpartum depression is defined as having five or more depressive symptoms for most days over a two-week period. Those symptoms include depressed mood, thoughts of suicide, difficulty making decisions, sleep problems, decrease in appetite and weight loss, feeling guilty or worthless, and extreme fatigue or lack of energy, among other symptoms. The condition affects 15 percent to 20 percent of women who give birth.

Postpartum depression also affects how a mother takes care of her new baby. She may be afraid to be alone with her child because of her symptoms or even think of harming the baby, she may worry constantly about the baby or not be interested in the baby’s welfare, according to the National Institutes of Health.

Who is more likely to suffer from postpartum depression? According to the NIH, the chances of developing the psychological condition are higher if a woman is under 20 years old; abuses alcohol, smokes or takes illegal substances; had an unplanned pregnancy; had a stressful event during pregnancy, including a death of a loved one or learning the baby has a birth defect; has a close relative with depression or anxiety; or had depression, bipolar disorder, or an anxiety disorder before the pregnancy or a previous pregnancy, among other risk factors.

Did postpartum depression cause Carey’s episode and eventual death in Washington, D.C.? It’s still too early to tell, noted Dr. Manny Alvarez of Fox News. But he said the incident should be a lesson for women not to neglect their mental health if they feel unwell after pregnancy.

“We don’t yet know all the facts in this case, but if it is true that this woman was suffering from postpartum depression and was receiving treatment that failed to improve her overall mental state, then [Thursday] was a tragedy that should give us all reason to pause and pay attention to mental health,” Diaz wrote.

Even more severe than postpartum depression is a condition known as postpartum psychosis. It’s defined as a “rare, severe and dangerous form of postpartum depression” that takes root within three weeks of giving birth, according to WebMD.

“A woman with postpartum psychosis may feel detached from her baby and other people; have hallucinations involving smell, touch, sight or hearing; have thoughts not based in reality (delusions); display bizarre behavior; or have urges to kill herself and her child or children,” the website notes. But it’s still unclear whether Miriam Carey was suffering from this form of postpartum depression.

Women with bipolar disorder are more likely to develop postpartum psychosis. WebMD warns that if the postpartum psychosis is not treated, the condition “can worsen rapidly and lead to dangerous, irrational behavior that a woman cannot control.”

The condition is viewed as a medical emergency that requires hospitalization.