Abstract / Summary
Project Personality and the Action Brings Change Project are two web-based single-session interventions (SSIs) with theoretically distinct targets (growth mindset, behavioral activation, respectively) that have been shown to reduce adolescent depressive symptoms. However, the mechanisms through which they exert their effects remain unclear. In this preregistered exploratory analysis, we used completer data for each SSI (ns = 653 and 730) from a trial in depressed adolescents to examine the total effects of three theoretically derived candidate factors (pre-post changes in agency, pre-post changes in hopelessness, and postintervention acceptability) on 3-month changes in depressive symptoms. To further clarify potential mechanisms, we used commonality analysis to separate the explained variance unique to each predictor from that shared across multiple predictors. In both SSIs, changes in hopelessness and agency each demonstrated significant, small total effects on depressive symptom change (R² range = 2.89-4.92%). Both predictors contributed significant unique explanatory variance (1.01-1.80%) and shared explanatory variance with each other (1.23-1.99%). By contrast, acceptability demonstrated a significant, very small total effect (1.48%) in only one SSI (comprised of significant explanatory variance shared with both other predictors; 1.01%) and no significant unique effect in either SSI. Overall, findings suggest that changes in hopelessness and agency have partially distinct, yet overlapping associations with longer-term changes in depressive symptoms following completion of either SSI, despite the SSIs’ theoretically distinct targets. Future research should evaluate a broader set of candidate mechanisms using intensive longitudinal designs and methods that can further clarify the magnitude and nature of the mechanisms’ pathways.