Exploring the Mediating Role of Working Alliance in a Peer Support Intervention for Late-Life Depression.

Objective: Peer support is an evidence-based intervention for depression, yet the mechanisms underlying its effectiveness remain understudied, particularly in randomized clinical trials. This study examined the mediating role of working alliance components (task, bond, and goal) for 45 participants who were administered the Peer Enhanced Depression Care (PEERS) intervention. Methods: These participants received eight weekly peer support meetings focused on enhancing self-care and increasing coping skills. Working alliance was assessed by both participants and peer coaches using the Working Alliance Inventory on a weekly basis during the 8-week intervention period. Structural equation modeling was used to assess the trajectory of working alliance subscales and whether the subscales (bond, agreement on tasks and goals) mediated depressive symptoms (PHQ-9 score). Results: Descriptive analysis showed that participants' and peer coaches' perceptions of working alliance differed on all three subscales (bond, agreement on goals and tasks) initially and increased and converged throughout the intervention period. Only agreement on goals as rated by peer coaches significantly mediated the relationship between the intervention and depressive symptoms. No participant-rated alliance subscales were significant mediators. Conclusions: Findings suggest that although bond may be a critical factor in alleviating symptoms of depression, agreement on goals may be a more crucial driver of change than emotional connection or agreement on tasks. Implications for intervention design and peer training include the importance of content and training on collaborative goal-setting in addition to relationship building with the participant to maximize clinical effectiveness. Trial Registration: This study was registered through ClinicalTrials.gov under registration number 2022P001675 under grant R01MH123165 on February 17th, 2020.