The incidence of depressive episodes is different before, during, and after pregnancy: A population-based study.

Background: Depressive episodes during pregnancy are widely investigated but it is still unknown whether pregnancy is a high-risk period compared to the pre-pregnancy period. Therefore, we aimed to investigate the incidence and recurrence of depressive episodes before, during, and after pregnancy.

Methods: In the current population-based registry study, we calculated monthly incidence and recurrence of psychiatric inpatient admissions and outpatient psychiatric contact for depressive episodes. We identified a population consisting of all first childbirths in Denmark from 1999 through 2015 (N = 392,287).

Results: Incidence of inpatient admission during pregnancy was lower than before pregnancy. After childbirth, a significant increase in first-time and recurrent psychiatric inpatient admissions was observed, especially in the first months. In contrast, outpatient psychiatric treatment incidence and recurrence were increased both during pregnancy as well as in the postpartum period, as compared to pre-pregnancy.

Limitations: Analyses were performed on depressive episodes representing the severe end of the spectrum, questioning generalizability to milder forms of depression treated outside psychiatric specialist treatment facilities.

Conclusion: We found a different pattern of severe episodes of depression compared to moderate episodes before, during, and after pregnancy. In light of our findings and those of others, we suggest distinguishing between timing of onset in the classification of depression in the perinatal period: Depression with pregnancy onset OR with postpartum onset (instead of the current DSM classifier "with perinatal onset"), as well as severity of depression, which is important for both clinical and future research endeavors.