Risk factors for treatment resistance among women with postpartum depression in a nationwide study

The occurrence of treatment resistance in women with postpartum depression (PPD) and risk factors for treatment resistance remain less studied. This study aimed to determine the rate of treatment resistance and the associated risk factors among women with PPD in a nationwide setting. Here we conducted a nationwide register-based cohort study of 58,618 patients with a first-ever PPD during 2006-2021 in Sweden. Information on demographics, pregnancy characteristics, pre-existing physical and psychiatric conditions and treatment was retrieved from Swedish national registers. The outcome was treatment-resistant PPD (TRPPD) within 1 year following PPD diagnosis. Associations between potential risk factors and TRPPD were assessed using multivariable Poisson regression. Among the 58,618 patients with PPD, 3,522 (6.0%) met the criteria for TRPPD during 1 year after PPD diagnosis. Lower educational level, lower household income, being non-cohabiting, smoking in early pregnancy, delivery by cesarean section, pre-existing physical conditions and pre-existing psychiatric disorders were significantly associated with a higher risk of TRPPD. In addition, patients with two births (versus primiparity) or with a prior premenstrual disorder had a lower risk of TRPPD. Treatment resistance in patients with PPD is common and is notably associated with specific demographic and clinical profiles. These findings may provide grounds for practical risk assessment at PPD diagnosis and highlight the need for personalized management strategies.