What is known about mediators, moderators and predictors of change in psychodynamic internet-delivered interventions for mental health? A systematic review and narrative synthesis.

Objective: This systematic review aims to synthesize and critically appraise existing research on mediators, moderators, and predictors of change in psychodynamic internet-delivered interventions (IDIs) for mental health. Methods: A systematic search of eight databases was conducted for studies published between January 2010 and May 2024 (PROSPERO ID: CRD42024533590). Results: Eleven studies met inclusion criteria, predominantly conducted in Sweden, and focused on therapist-guided psychodynamic IDIs. The most frequently studied mediators included emotion regulation, emotion processing, and therapeutic alliance, with evidence suggesting that improvements in emotion regulation and processing significantly mediate symptom reduction. Few studies examined moderators, with limited evidence that demographic variables influence outcomes. Significant predictors of change included baseline emotion regulation difficulties, which were associated with greater symptom improvement, and therapeutic alliance, which predicted treatment response. Conclusion: Findings highlight the role of emotional processing and regulation as possible mechanisms of change, aligning with theoretical models of psychodynamic therapy. The relationship between alliance, emotional change processes, and treatment outcomes points to the importance of the therapeutic relationship in facilitating change. The small and heterogeneous evidence base makes it difficult to draw firm conclusions, but highlights a need for methodologically rigorous and theory-driven research to clarify causal pathways and optimize intervention effectiveness.