Identifying components of modularized psychological interventions that contribute to symptom reduction is essential to improving depression treatment. In a secondary analysis of a randomized controlled trial (RCT), session-specific effects of Metacognitive Training-Silver, a group intervention for older adults with depression, were investigated. Thirty-eight older adults with major depressive disorder or dysthymia participated in up to eight sessions of MCT-Silver. A clinical assessment of depressive symptoms (Hamilton Depression Rating Scale) as well as additional interviews and questionnaires administered as part of the RCT were completed at pre- and post-intervention. Depressive symptoms, negative (meta)cognitive beliefs, emotion regulation strategies and attitudes toward aging were assessed pre- and post-session. The rate of change in each variable per module, elevation following the module in which the variable was addressed, and the rate of change post module were examined via linear mixed models. Clinician-rated depressive symptoms were significantly reduced from pre- to post-intervention (Cohens d = 1.31). Self-reported depression and negative mental filter measured within sessions improved significantly over treatment, whereas black-and-white thinking improved after module #3 (Should Statements, All or Nothing Thinking and Acceptance). Module-specific within-session effects were found for overgeneralization (module #1: Mental Filter) and rumination (module #6: Rumination and Social Withdrawal). Improvement in mental filter in module #1 was significantly associated with depression reduction. This study provides initial evidence that MCT-Silver partially meets its aims of reducing depression and specific cognitive variables within and across sessions. Improvement of the instrument used to measure change may improve detection of module-specific effects.Trial registration: NCT03691402.
