Background: Insomnia is prevalent during pregnancy and the postpartum period and contributes to vulnerability for anxiety and depressive disorders during this time. However, the mechanisms linking sleep disturbance to depressive and anxiety symptoms remain unclear. Emotion dysregulation (ED) and pre-sleep arousal have been proposed as key transdiagnostic processes. This is the first study to integrate daily and longitudinal methods to examine these mechanisms across the perinatal period.Methods: Data were drawn from a randomized controlled trial evaluating two brief interventions for insomnia during pregnancy and the postpartum. Seventy-five pregnant individuals were assessed across pregnancy and the postpartum using trait measures and 7-day daily surveys at three timepoints. Regression models examined whether prenatal insomnia, ED, and their interaction predicted postpartum depression, anxiety, and worry. Multilevel models tested within-person associations between daily sleep and next-day symptoms, with ED as a moderator, and cluster bootstrap mediation analyses examined pre-sleep arousal as a mediator of sleep–symptom associations.Results: For postpartum anxiety symptoms, higher prenatal insomnia and ED independently predicted symptoms, with a significant interaction (β = .28, p = .003). For postpartum depressive symptoms, only the insomnia × ED interaction was significant (β = .23, p = .045). For postpartum worry, only baseline worry predicted outcomes. At the within-person level, sleep quality and sleep onset latency predicted next-day anxiety and depression; ED did not moderate these associations. Mediation analyses indicated that daytime anxiety and depressive symptoms predicted poorer sleep quality, sleep onset latency, and sleep efficiency through increased pre-sleep arousal.Conclusions: Findings support a pathway linking insomnia and ED to perinatal anxiety and depression. Results suggest that prenatal ED is associated with heightened vulnerability to the mental health consequences of insomnia and identify pre-sleep arousal as a key mechanism linking daytime affect to sleep disruption. Clinical implications for perinatal mental health are discussed.
