INTRODUCTION: Paternal postpartum depression may affect 28% of fathers, but its temporal association with maternal postpartum depression is not well understood. This study aimed to quantify the temporal association between maternal postpartum depression and paternal postpartum depression, considering mother's depression history and other clinical factors. METHODS: Data for this retrospective cohort study were obtained from Kaiser Permanente Colorado health records between 2008 and 2019. The cohort included father-mother dyads having live-birth pregnancies. Diagnostic codes identified postpartum depression during the 12 months after childbirth. Complementary log-log models with inverse probability of treatment weighting estimated the relative risk of paternal postpartum depression by maternal postpartum depression, stratified by maternal depression history. Statistical analyses were performed between 2022 and 2024. RESULTS: The sample included 15,257 father-mother dyads contributing 19,352 pregnancies, in which neither parent had a history of postpartum depression. Among these pregnancies, 326 paternal postpartum depression diagnoses (1.7%) and 1,731 maternal postpartum depression diagnoses (8.9%) were identified. Paternal postpartum depression was more common in dyads with maternal postpartum depression (3.0%) than in dyads without (1.6%). Maternal postpartum depression was associated with an 81% increase in paternal postpartum depression (relative risk=1.81
95% CI=1.14, 2.87) if the mother had no history of depression. However, no association was observed if the mother had a history of depression. CONCLUSIONS: Among a cohort of father-mother dyads having live-birth pregnancies, maternal postpartum depression was associated with increased paternal postpartum depression but only if the mother had no history of depression. Study findings highlight the need to develop depression screening tools for fathers that consider risk factors for both parents.