The American College of Obstetrics and Gynecology now recommends that women be screened for depression during pregnancy in addition to screening during the postpartum period. Because depressive symptoms during pregnancy have been associated with worse outcomes and are a robust predictor of postpartum depression, the identification of women with depression during pregnancy would help us to identify and treat women with symptoms during pregnancy and those who are at high risk for depressive illness during the postpartum period.
The Edinburgh Postnatal Depression Scale (EPDS) is one of the tools most commonly used to screen for depression in this setting. This is a 10-item questionnaire which has been validated in many different populations and i able in almost every language. On this scale, a score of 10 or greater or an affirmative answer on question 10 (presence of suicidal thoughts) is suggestive of depression. (Setting the cut-off score of 12 improves the ability of the EPDS to identify major depression; however, the sensitivity falls off significantly, making it less useful for the purposes of screening because it increases the number of false positives.)
Most importantly it should be emphasized that the EPDS is a screening tool, and elevated score on the EPDS does not necessarily confirm the diagnosis of depression; this requires a more thorough diagnostic evaluation. While in some settings, women who screen positive can be evaluated by a mental health professional in a timely manner, many obstetric practices have limited access to providers with expertise in this area.
We have long been concerned that overreliance on or misuse of screening tools like the EPDS might lead to misdiagnosis and misguided treatment. Not all of the women who would be picked up when screening for depression with the EPDS actually have unipolar depression. In particular, we are concerned that some of these women who screen positive for depression may have bipolar disorder or other psychiatric diagnoses.
Lydsdottir and colleagues have examined the psychiatric diagnoses of women who were identified with probable depression using the EPDS during pregnancy. A total of 2,411 women receiving their antenatal care in primary care clinics completed the EPDS. In this group 235 of the women (9.7%) screened positive (EPDS > 12) at gestational week 16.
Of the women who screened positive, 153 (66%) agreed to a psychiatric diagnostic interview. Among the who screened positive, the following diagnoses were identified:
- Major depressive disorder – 31.4%
- Bipolar disorder – 13.1%
- Anxiety disorders – 60.8%, including OCD (17.6%)
- Dysthymia – 5.2%
- Somatoform disorder – 11.8%
- Current substance abuse – 4.6%
- Eating disorder – 2.0%
It is quite striking that in this study, only about a third of the women who screened positive actually had unipolar depression. In other words, if we were using the EPDS as our only tool to guide diagnosis and treatment, we would be wrong 70% of the time.
While the EPDS has been validated for use during pregnancy, this study shows us that it may have some serious limitations when used as a screening tool for depression in this setting. In another study where the EPDS was used to screen postpartum women, about a third of the women with a positive screen on the EPDS did not have unipolar depression but actually had bipolar disorder.
It would be unfortunate to either miss or misidentify women with bipolar disorder who present with active symptoms during pregnancy or the postpartum period. This population is at extremely high risk for postpartum psychiatric illness, including postpartum psychosis. Because what we might recommend for women with bipolar disorder differs dramatically from what we would consider for women with unipolar depression, this sort of misdiagnosis could have disastrous results.
If we are to pursue universal screening of pregnant and postpartum women, we must make sure an adequate treatment network is in place first. We must ensure that obstetrics services have access to mental health professionals with expertise in this area and that psychiatric evaluation can occur in a timely fashion.
Ruta Nonacs, MD PhD
Lydsdottir LB, Howard LM, Olafsdottir H, Thome M, Tyrfingsson P, Sigurdsson JF. The mental health characteristics of pregnant women with depressive symptoms identified by the Edinburgh Postnatal Depression Scale. J Clin Psychiatry. 2014 Apr;75(4): 393-8.