Having babies can sometimes keep personal problems at bay.

"[It] keeps you busy — if not through adoption, than in pregnancy, you get the oxytocin [often called the 'hormone of love'] bursts," said Honos-Webb. "You get attention from other people and you define your own role — all those things manage depression."

Often subclinical depression is not obvious to the person, according to Honos-Webb. "It's difficult to admit those feelings, especially if you have a healthy child and every reason to be happy."

Having children to find happiness is a "recipe for a mental health disaster," according to Honos-Webb, who coins the phenomenon a "Mother Theresa complex." The result can be a failure to attach emotionally, causing eating disorders and depression in the children.

"There is such an imbalance to give and not to take," she said. "On the one hand, Mother Theresa was a saint, but on the other hand, it was a perfect formula for major depression."