For women the postpartum period is a time of increased vulnerability to mood disorders.  Recent estimates indicate that about 20% of women will suffer from significant depressive symptoms during the year after the birth of a child.  Despite a significant push over the last decade to identify and effectively treat women with mood disorders during pregnancy and the postpartum period, treatment rates in this population remain unacceptably low.  Furthermore, questions still remain regarding the optimal timing of screening and the best instruments to be used in this setting.

In a recent study, Wisner and colleagues at the University of Pittsburgh screened for depression in postpartum women using the Edinburgh Postnatal Depression Scale (EPDS).  Women with positive screens were evaluated in order to determine the timing of episode onset, the prevalence and intensity of self-harm ideation, and the primary and secondary DSM-IV diagnoses.

Ten thousand postpartum women underwent screening at 4 to 6 weeks postpartum.  1396 women (14.0%) had positive screens – defined as an EPDS score of 10 or higher or having thoughts of harming oneself as assessed in item 10 of the EPDS. Women with positive screens underwent evaluation with the Structured Clinical Interview for DSM-IV for Axis I diagnoses (SCID); 826 (59.2%) completed the home visits and 147 (10.5%) completed a telephone diagnostic interview.

Women with positive screens were more likely to be younger, African American, publicly insured, single, and less well educated.

A significant proportion of depressive episodes had their onset prior to delivery:

  • 40.1% of the episodes began during the postpartum period
  • 33.4% of the episodes had their onset during pregnancy
  • 26.5% of the episodes began before pregnancy and had a more chronic pattern

Women with positive screens had the following psychiatric diagnoses (identified using the SCID):

  • The most common primary diagnosis was unipolar depression (68.5%)
  • Almost two-thirds of women with MDD had comorbid anxiety disorders, most commonly generalized anxiety disorder
  • 22.6% of the women were diagnosed with bipolar disorder
  • Only 2.1% had no primary axis I diagnosis

The prevalence of self-harm ideation was also assessed:

  • 19.3% of the women endorsed thoughts of harming themselves
  • All mothers with the highest intensity of self-harm ideation had EPDS score of 10 or higher.

This study, including 10,000 new mothers, is the largest ever carried out in the United States using screening with the EPDS. This study has some limitations, most notably that a significant proportion of the women (about 30%) did not receive a post-screening diagnostic evaluation.  The authors note that some women declined screening because they were already receiving mental health treatment.  While these issues may contribute to a less accurate estimate of the prevalence of postpartum depression, this study has yielded valuable information which can inform our approach to screening during the postpartum period.

Interestingly, other studies have used a higher cutoff for the EPDS, typically 12.  While there has been concern that using a lower cutoff score may increase the prevalence of false positives and, as a result, may divert important mental health resources to women who don’t actually need them, this study actually shows a very low rate of false positives (2.1%).  Although some of the women who screened positive did not have a primary mood disorder (about 5%), they were diagnosed with other psychiatric disorders, such as an anxiety disorder or substance use disorder.  Reassuringly an EPDS cut-off score of 10 also reliably identified all women with the most intense thoughts of self-harm.

As to the ideal timing of screening, this study suggests that we might be better off screening during pregnancy, as well as during the postpartum period.  Almost two thirds of the women who reported depressive symptoms during the postpartum period also had depressive symptoms during pregnancy.  Identifying women before childbirth may also allow us to implement interventions which may decrease the intensity of postpartum symptoms or minimize their impact on the family.

One of the most significant contributions of this large study is the detailed picture it provides of the psychiatric diagnoses associated with an elevated score on the EPDS.  The EPDS was designed to be a screening tool and is no substitute for a diagnostic interview.  This study indicates that while the majority of women with a positive screen have a diagnosis of a mood disorder, some do not.  Most importantly this data indicates that a large number of women with a positive screen actually have bipolar disorder.  With regard to treatment selection, it would be a potentially serious error to assume that all women with a positive EPDS screen have unipolar depression given that nearly one quarter of the women have bipolar disorder.  Further research will be required to determine if the EPDS can be combined with other screening tools to better identify women with bipolar disorder.

The findings of this study indicate that the EPDS (with a cutoff score of 10) could be used to screen during pregnancy and at 4-6 weeks postpartum.  (Some studies show that we may be able to screen as early as one week postpartum.)  We know from previous studies that screening with an EPDS will typically pick up over 90% of cases of PPD, and this study indicates that using a cutoff score of 10 picks up those women with the most intense self-harm ideation.  While the majority of women with a positive screen will have some type of mood disorder, making appropriate treatment recommendations depends upon a more thorough diagnostic evaluation in order to identify bipolar disorder and comorbid anxiety disorders.

Ruta Nonacs, MD PhD

Wisner KL, Sit DKY, McShea MC, et al.  Onset Timing, Thoughts of Self-harm, and Diagnoses in Postpartum Women With Screen-Positive Depression Findings.  JAMA Psychiatry 2013.