The term postpartum depression is used generically to denote occurrence of a depressive episode after childbirth. Emerging research suggests that bipolar disorder is common among women with postpartum depression. Due to the lack of awareness of its existence, bipolar postpartum depression is often misdiagnosed as major depressive disorder, causing long delays for women to receive appropriate treatment. We hypothesize that screening all women with postpartum depression for bipolar disorder would help correctly identify subgroups of women based on the underlying psychiatric diagnosis. This suggested approach could improve the outcome of postpartum depression and facilitate timely disorder-specific treatment interventions.

Introduction

Approximately 6.5%–۱۲٫۹% of women have a major or minor depressive episode in the first 12 months postpartum [1]. Depression may begin for the first time after childbirth; however, for the vast majority of women it is a recurrence of either major depressive disorder or bipolar disorder. Depression is the most common type of recurrence in women with bipolar disorder [2]. In one study, nearly 19% of women with bipolar I disorder, and 29% of women with bipolar II disorder had episodes of major depression after childbirth in spite of prophylactic drug treatment [3]. Postpartum depression (PPD) has historically been considered a manifestation of major depressive disorder; however, recent research developments have prompted a reappraisal of the diagnostic status of PPD. By allowing the use of the peripartum-onset specifier (occurrence of a depressive episode during pregnancy or first four weeks postpartum) to denote cases of bipolar II disorder in addition to major depressive disorder and bipolar I disorder, the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [4] has expanded the repertoire of PPD and highlighted the need to differentiate between unipolar depression and subtypes of bipolar depression.

Childbirth and ubiquity of hypomania

Hypomanic symptoms occur in 9.6%–۲۰٫۴% of women after childbirth [5]. The unique role of childbirth in the induction of hypomanic symptoms was highlighted in a longitudinal study from the United Kingdom that found an eight-fold increase in the prevalence of hypomanic symptoms in the first week postpartum compared to during pregnancy; however, there was no significant increase in cases of depression from pregnancy to the postpartum period [6]. The majority of studies on postpartum hypomania have used the Highs scale, a self-rating scale based on the Schedule for Affective Disorders and Schizophrenia-Lifetime Version [5]. Currently, there are no studies on the prevalence of postpartum hypomania using the DSM-5 diagnostic criteria. Similarly lacking are studies on the DSM-5 diagnostic profile of women with hypomanic symptoms in the postpartum period. Also, we do not know whether hypomanic symptoms can occur alone, or are invariably accompanied by depressive episodes. Notwithstanding the lack of studies addressing these issues, it is clear that the hypomanic symptoms are followed by depressive episodes in some women [7]. Glover and colleagues [7] reported that 50% of women with hypomanic symptoms, compared with 18% of women without these symptoms in the first postpartum week, scored 10 or higher on the Edinburgh Postnatal Depression Scale (EPDS) at six weeks postpartum. Using an EPDS cut off of 13, another study found that 25% of women with hypomanic symptoms after childbirth compared with 5.2% of women without these symptoms had depressive symptoms at eight weeks postpartum [8].