For women, the postpartum period appears to be a time of increased risk for conversion to bipolar disorder in women previously diagnosed with major depressive disorder. Sharma and colleagues observed that the rate of diagnostic switching to bipolar II disorder occurred in 6.52% of women during the first six months after childbirth, which is at least 11- to 18-fold times higher than the rates of switching observed in similar studies conducted in non-puerperal women.
Given that women with bipolar disorder are at risk for severe symptoms after childbirth, including postpartum psychosis, it is crucial to be able to distinguish unipolar from bipolar illness in this setting. This can be particularly challenging in that many women with postpartum depression also exhibit intense anxiety which may be difficult to distinguish from mixed symptoms.
In the study from Sharma and colleagues, bipolar switch was more common in women with a family history of bipolar disorder. This is consistent with other studies of bipolar switching in non-puerperal populations of women. Thus we must question all women about family history of psychiatric illness, including bipolar disorder, and we must ask not just about postpartum illness but must inquire more broadly about history of psychiatric illness in both male and female relatives.
While obtaining information on family history is clearly an important aspect of assessment, we must acknowledge that it is often difficult to obtain accurate information about family history of psychiatric illness. A recent study suggests that biomarkers may aid the early identification of women at high risk of conversion from unipolar depression to bipolar disorder. In this prospective study, serum levels of nerve growth factor or NGF were higher in women who converted to bipolar disorder compared to the women with remitted MDD or current MDD.
While this study did not specifically look at pregnant or postpartum women, one wonders if these biomarkers may be helpful in terms of identifying women at risk for bipolar switch during the postpartum period or may be useful for distinguishing bipolar illness from unipolar depression in women with postpartum depression associated with high levels of anxiety.
Ruta Nonacs, MD PhD
Pedrotti Moreira F, Cardoso TC, Mondin TC, Wiener CD, de Mattos Souza LD, Oses JP, Jansen K, da Silva RA. Serum level of nerve growth factor is a potential biomarker of conversion to bipolar disorder in women with major depressive disorder Psychiatry Clin Neurosci. 2019 Sep;73(9):590-593.
Sharma V, Xie B, Campbell MK, Penava D, Hampson E, Mazmanian D, Pope CJ. A prospective study of diagnostic conversion of major depressive disorder to bipolar disorder in pregnancy and postpartum. Bipolar Disord. 2014 Feb;16(1):16-21
Potential Biomarker for Early Detection of Bipolar Disorder in Women With MDD (Psychiatry Advisor)