Add a colicky baby, or a lack of emotional support, and you have a one-way ticket to the blues. Motherhood is most disorienting for first-time moms. Not surprisingly, they are at unusually high risk of post-partum emotional problems. Hormones also play a role. High levels of female sex hormones circulate in expectant mothers' blood, but drop precipitously within hours of delivery, contributing to biochemical depression.
Pregnancy also increases levels of endorphins, the body's feel-good chemicals.
Endorphin levels fall abruptly after delivery, adding to risk of depression. Finally, a history of depression increases risk. Oddly, until recently, mental health professionals have paid scant attention to post-partum depression. The American Psychiatric Association didn't even officially recognize the condition until the 1994 edition of the organization's Diagnostic and Statistical Manual of Mental Disorders. But today, post-partum depression is much better publicized.