Importance: Maternal postnatal depression (PND) is common and associated with adverse child outcomes. These effects are not inevitable, and it is critical to identify those most at risk. Previous work suggests that the risks of adverse outcomes are increased when PND is severe and persistent, but this has not been systematically studied. Objective: To examine the association between differing levels of persistence and severity of PND and long-term child outcomes. Design, Setting, and Participants: The sample for this observational study comprised participants in the Avon Longitudinal Study of Parents and Children in the United Kingdom. Three thresholds of PND severity-moderate, marked, and severe-were defined using the self-rated Edinburgh Postnatal Depression Scale (EPDS). Depression was defined as persistent when the EPDS score was above the threshold level at both 2 and 8 months after childbirth. For each of these severity and persistence categories, the following were examined: (1) the trajectories of later EPDS scores (6 time points between 21 months and 11 years after childbirth) and (2) child outcomes-behavioral problems at 3.5 years of age, school-leaving mathematics grades at 16 years of age, and depression at 18 years of age. Data analysis was conducted from July 12, 2016, to February 8, 2017. Main Outcomes and Measures: Child behavioral problems at 3.5 years of age using the Rutter total problems scale, school-leaving mathematics grades at 16 years of age extracted from records of external national public examinations, and offspring depression at 18 years of age using the Clinical Interview Schedule-Revised. Results: For the 9848 mothers in the sample, the mean (SD) age at delivery was 28.5 (4.7) years. Of the 8287 children, 4227 (51%) were boys and 4060 (49%) were girls. Compared with women with PND that was not persistent and women who did not score above the EPDS threshold, for all 3 severity levels, women with persistent PND showed elevated depressive symptoms up to 11 years after childbirth. Whether persistent or not, PND doubled the risk of child behavior disturbance. The odds ratio (OR) for child behavioral disturbance for mothers with moderate PND was 2.22 (95% CI, 1.74-2.83), for mothers with marked PND was 1.91 (95% CI, 1.36-2.68), and for mothers with severe PND was 2.39 (95% CI, 1.78-3.22). Persistence of severe PND was particularly important to child development, substantially increasing the risk for behavioral problems at 3.5 years of age (OR, 4.84; 95% CI, 2.94-7.98), lower mathematics grades at 16 years of age (OR, 2.65; 95% CI, 1.26-5.57), and higher prevalence of depression at 18 years of age (OR, 7.44; 95% CI, 2.89-19.11). Conclusions and Relevance: Persistent and severe PND substantially raises the risk for adverse outcome on all child measures. Meeting criteria for depression both early and late in the postnatal year, especially when the mood disturbance is severe, should alert health care professionals to a depression that is likely to be persistent and to be associated with an especially elevated risk of multiple adverse child outcomes. Treatment for this group should be prioritized.
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