Some studies have suggested that those with PMDD are more at risk of developing postpartum depression after pregnancy, but other evidence has been found to suggest against that notion. PMDD was added to the list of depressive disorders in the "Diagnostic and Statistical Manual of Mental Disorders" in 2013. It has 11 main symptoms, and a woman has to exhibit at least five to qualify for PMDD. Roughly 20% of menstruating women have some symptoms of PMDD, but either have less than five or do not have functional impairment.