Association Between Expressed Emotion and Relapse of Bipolar Disorder: A Systematic Review.

Background: Expressed emotion (EE) is a robust predictor of relapse in individuals with schizophrenia-spectrum disorders. However, the evidence on this relationship has not been fully examined in individuals with bipolar disorder (BD). This systematic review was conducted to provide updated evidence on the association between EE and relapse in BD. Methods: A systematic search was conducted in seven databases and two registries from inception to 29 December 2025. The Joanna Briggs Institute's (JBI) critical appraisal checklists were used to assess the risk of bias in the included studies. The review process was conducted independently by two reviewers, with consensus for each step achieved through consultation with a third reviewer. A narrative synthesis was performed to categorise the findings, with particular focus on the impact of global EE and its subdomains on relapse in BD. Results: Of the 2963 records identified, seven studies were included in this review. The majority of studies were rated as having a low risk of bias. The narrative synthesis indicates that high EE is significantly associated with an increased risk of relapse in BD, particularly for depressive episodes, and is linked to critical comments and emotional over-involvement, two key subdomains of EE. Conclusions: This review provides evidence of a potential association between high EE, its subdomains, and relapse in BD. These preliminary findings contribute to the development of family-based interventions for BD and highlight the need for larger-scale, longitudinal prospective cohort studies to further clarify this relationship. Registration: The study has been registered on https://www.crd.york.ac.uk/prospero/ (registration number: CRD42025632303; registration link: https://www.crd.york.ac.uk/PROSPERO/view/CRD42025632303).