Timing of antidepressant initiation postpartum and maternal mental health outcomes up to 18 months after childbirth

Evidence on postpartum antidepressant effectiveness is limited. We sought to determine the association between different timings of antidepressant initiation within the 0–6 months postpartum and mental outcomes at 6- and 18-months following childbirth. Using data from the Norwegian Mother, Father and Child Cohort Study (MoBa) linked to a sub-sample of MoBa Genetics, we included 1146 women with psychiatric history before and/or during early pregnancy: 154 (13.4%) antidepressant initiators in the 0–6 months postpartum (37.0% within 0–3, and 63.0% within 4–6 months), and 992 (86.6%) with unmedicated new mental illness episode within same period. Depression/anxiety symptom outcomes at 6 and 18 months postpartum were self-reported. To control for measured confounding, we fit linear and modified Poisson models using overlap weighting, overall and stratified by polygenic score for antidepressant response. Antidepressant initiators within 0–3 months postpartum had reduced severity of depression/anxiety symptoms at 6, but not at 18 months postpartum, compared with unmedicated women (weighted mean difference (MD): -0.23, 95% CI = -0.39, -0.06) and a 44% lower risk of having active, clinically relevant depressive/anxiety symptoms at 6 months (weighted RR= 0.56, 95% CI = 0.35, 0.91). No association was observed for initiation at 4–6 months postpartum at the 6-month assessment. The associations were evident only among women having high polygenic score for positive antidepressant response (weighted MD: -0.50, 95% CI: -0.84, -0.16), and that persisted at 18 months. Initiation of antidepressant in first 3 months postpartum, but not in months 4–6, is associated with reduced severity of depression/anxiety symptoms at 6 months post-delivery. Effects were most evident among women with higher polygenic scores; however, these findings are exploratory and warrant larger studies.