Postpartum blues- when does it become dangerous?

After giving birth, your hormones are the first thing to take a nose dive. When this happens, you may feel sad or lonely for a little while. But this becomes dangerous when these feelings don't go away after a few days. In the past few years, the rate of postpartum depression has increased and it is vital that we acknowledge this so we can help mothers around us. So, how do we recognize the symptoms of postpartum blues?