Does Childbirth Cause Psychiatric Disorders? A Population-based Study Paralleling a Natural Experiment

Background: Childbirth is associated with increased risk of first-time psychiatric episodes, and an unwanted pregnancy has been suggested as a possible etiologic contributor. To what extent childbirth causes psychiatric episodes and whether a planned pregnancy reduces the risk of postpartum psychiatric episodes has not been established. Methods: We conducted a cohort study using data derived from Danish population registers, including all women having in vitro fertilization (IVF) treatment and their partners with recorded information in the IVF register covering fertility treatments in Denmark at all public and private treatment sites from January 1994 to December 2005. We compared parents and childless persons to examine whether childbirth is directly associated with onset of first-time psychiatric episodes, with incidence rate ratios (risk of first psychiatric inpatient or outpatient treatment) as the main outcome measures. Results: The incidence rate for any type of psychiatric disorder 0 to 90 days postpartum was 11.3 per 1000 person-years (95% confidence interval = 8.2-15.0), and 3.8 (3.4-4.3) among women not giving birth. IVF-treated mothers had an increased risk of a psychiatric episode postpartum (incidence rate ratio [IR] = 2.9 [2.0-4.2]) compared with the risk of psychiatric episodes in childless women. Risk of psychiatric episodes later than 90 days postpartum was decreased (IR = 0.9 [0.7-1.0]). Conclusions: Using a study design paralleling a natural experiment, our results showed that childbirth is associated with first-time psychiatric disorders in new mothers, indicating that a planned pregnancy does not reduce risks of or prevent postpartum psychiatric episodes.