While the exact cause of PPD is unclear, the cause is believed to be a combination of physical, emotional, genetic, and social factors. These may include factors such as hormonal changes and sleep deprivation. Risk factors include prior episodes of postpartum depression, bipolar disorder, a family history of depression, psychological stress, complications of childbirth, lack of support, or a drug use disorder. Diagnosis is based on a person's symptoms. While most women experience a brief period of worry or unhappiness after delivery, postpartum depression should be suspected when symptoms are severe and last over two weeks.