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NIMH: Population study finds depression is different before, during, after pregnancy

In Community, News by OC Monitor Staff

BETHESDA, Md. — Perinatal depression is a common but serious mood disorder. The DSM-5, which is the classification system used to diagnose mental disorders, defines perinatal depression as a depressive episode with onset either during pregnancy or in the first 4 weeks after pregnancy (postpartum). However, pregnancy and postpartum are associated with different hormonal, behavioral, and emotional changes. Combining them into a single disorder may make studying and treating depression more difficult. Additionally, restricting the postpartum period to the first month after childbirth may miss many women who continue to experience depressive symptoms beyond this time point.

New research funded by the National Institute of Mental Health examined the current classification of perinatal depression by looking at population-level rates of depression over an extended period. The study, led by Veerle Bergink, M.D., Ph.D., at the Icahn School of Medicine at Mount Sinai and the Erasmus Medical Center, compared depressive episodes among new mothers before, during, and after pregnancy.

The researchers used data from population registries in Denmark to identify 392,287 women who had given birth for the first time between 1999 and 2015. Only first-child births were included to avoid counting the same woman more than once. Then, the researchers calculated the number of first-time and repeat depressive episodes women experienced during each of the following months, reflecting three separate periods:

  • 12 months before pregnancy (preconception)
  • 9 months before to birth (pregnancy)
  • 12 months after birth (postpartum)

First-time and repeat depressive episodes were classified based on the number of times women sought psychiatric care for a new depressive episode or after having previously received depression treatment. The researchers calculated these rates separately for treatment at outpatient and inpatient psychiatric facilities. In this study, most treatment took place at outpatient facilities, reflecting care for moderate to severe depression, with only the most severe episodes treated at inpatient facilities.

Overall, treatment rates for first-time depressive episodes exceeded rates for repeat depressive episodes, regardless of the period (preconception, pregnancy, or postpartum). This was especially true during the postpartum period. First-time depressive episodes treated in outpatient and inpatient facilities rose substantially after childbirth and peaked at 2 months postpartum. The number of outpatient visits for first-time depression was also higher during pregnancy (especially in the second trimester) than before pregnancy.

Outpatient and inpatient visits for repeat depression were relatively consistent from month to month in both the preconception and postpartum periods. However, women who had previously received depression treatment sought more outpatient care for depression during pregnancy than they had before becoming pregnant. Unlike first-time depressive episodes, for which treatment rates were highest in the postpartum period, for repeat depressive episodes, most outpatient visits were received during the second trimester of pregnancy.

This study’s findings support the idea that pregnancy and postpartum are risk periods for maternal mental health. The results also point to a change in depressive episodes from pregnancy to after birth, specifically, a high onset of new depressive episodes in the second trimester of pregnancy and the first 5 months postpartum. This finding may have important implications for clinical care. A high rate of depressive episodes during pregnancy and after delivery underscores the vulnerabilities of both periods for new mothers and the need for access to readily available and comprehensive mental health care.

Moreover, the data showed a significant rise in depression treatment well into the postpartum period with rates higher than during pregnancy or preconception for several months after delivery. Because this is outside the clinical window in which perinatal depression can officially be diagnosed, the authors suggest extending the assessment of depression beyond 4 weeks postpartum, which may identify many more women who could benefit from treatment. Distinguishing between depression with pregnancy onset and depression with postpartum onset could also refine the diagnoses to better capture differences in their rates and presentation.

Although the findings add to our knowledge of depression that occurs before, during, and after pregnancy, the study has a few limitations. For example, the researchers analyzed population data from Denmark—a country with specific perceptions around and systems of mental health care—and the results may not generalize to other countries. In addition, the sample was limited to women who had given birth for the first time and were experiencing depressive episodes at the severe end of the spectrum (those treated in psychiatric facilities). The incidence and recurrence of depression may differ for women who have already given birth or with milder forms of depression.

More research is needed to understand how rates of depression vary in different locations and for different groups. Population-level studies that systematically explore depression and other mental health disorders can provide insights that lead to improved diagnosis and treatment.