Duration
Postpartum blues may last a few days up to two weeks. If symptoms last more than two weeks, the individual must be evaluated for postpartum depression. Causes
The causes of postpartum blues have not been clearly established. Most hypotheses regarding the etiology of postpartum blues and postpartum depression center on the intersection of the significant biological and psychosocial changes that occur with childbirth. Psychosocial causes
Pregnancy and postpartum are significant life events that increase a womans vulnerability for postpartum blues. Even with a planned pregnancy, it is normal to have feelings of doubt or regret, and it takes time to adjust to having a newborn. Feelings commonly reported by new parents and lifestyle changes that may contribute to developing early postpartum mood symptoms include:
Fatigue after labor and delivery
Caring for a newborn that requires 24/7 attention
Sleep deprivation
Lack of support from family and friends
Marital or relationship strain
Changes in home and work routines
Financial stress
Unrealistic expectations of self
Societal or cultural pressure to "bounce back" quickly after pregnancy and childbirth
Overwhelmed and questioning ability to care for baby
Anger, loss, or guilt, especially for parents of premature or sick infants

Risk factors
Most risk factors studied have not clearly and consistently demonstrated an association with postpartum blues. These include sociodemographic factors, such as age and marital status, obstetric factors, such as delivery complications or low birth weight.Factors most consistently shown to be predictive of postpartum blues are personal and family history of depression.
Epidemiology
Bipolar disorder is the sixth leading cause of disability worldwide and has a lifetime prevalence of about 1 to 3% in the general population. However, a reanalysis of data from the National Epidemiological Catchment Area survey in the United States suggested that 0.8% of the population experience a manic episode at least once (the diagnostic threshold for bipolar I) and a further 0.5% have a hypomanic episode (the diagnostic threshold for bipolar II or cyclothymia). Including sub-threshold diagnostic criteria, such as one or two symptoms over a short time-period, an additional 5.1% of the population, adding up to a total of 6.4%, were classified as having a bipolar spectrum disorder. A more recent analysis of data from a second US National Comorbidity Survey found that 1% met lifetime prevalence criteria for bipolar I, 1.1% for bipolar II, and 2.4% for subthreshold symptoms. Estimates vary about how many children and young adults have bipolar disorder. These estimates range from 0.6 to 15% depending on differing settings, methods, and referral settings, raising suspicions of overdiagnosis. One meta-analysis of bipolar disorder in young people worldwide estimated that about 1.8% of people between the ages of seven and 21 have bipolar disorder. Similar to adults, bipolar disorder in children and adolescents is thought to occur at a similar frequency in boys and girls.There are conceptual and methodological limitations and variations in the findings.