Postpartum depression isn’t always postpartum. It isn’t even always depression. A fast-growing body of research is changing the very definition of maternal mental illness, showing that it is more common and varied than previously thought.

Scientists say new findings contradict the longstanding view that symptoms begin only within a few weeks after childbirth. In fact, depression often begins during pregnancy, researchers say, and can develop any time in the first year after a baby is born.

Recent studies also show that the range of disorders women face is wider than previously thought. In the year after giving birth, studies suggest, at least one in eight and as many as one in five women develop symptoms of depression, anxiety, bipolar disorder, obsessive-compulsive disorder or a combination. In addition, predicting who might develop these illnesses is difficult, scientists say. While studies are revealing clues as to who is most vulnerable, there are often cases that appear to come out of nowhere.

As public awareness has grown, often spiking after a mother kills herself or her baby, a dozen states, including Illinois, New Jersey, Texas and Virginia, have passed laws encouraging screening, education and treatment, and New York and others are considering action. The federal Affordable Care Act contains provisions to increase research, diagnosis and care for maternal mental illness.