Single-session interventions (SSIs) can help reduce youth psychopathology, but SSIs may benefit some youths more than others. Identifying predictors of SSIs' effectiveness may clarify youths' likelihoods of benefitting from an SSI alone, versus requiring further treatment. We tested whether pre-to-post-SSI shifts in hypothesized symptom change mechanisms predicted subsequent reductions in youth internalizing symptoms. Data were from a trial evaluating whether an SSI teaching growth mindset (the belief that personality is malleable) reduced youth anxiety and depression. Youths (N = 96, ages 12-15) self-reported growth mindsets, perceived primary control, and perceived secondary control pre- and immediately post-intervention. They self-reported depression and anxiety symptoms at pre-intervention and 3, 6, and 9-month follow-ups. Larger immediate increases in primary control predicted steeper depressive symptoms declines across the follow-up; larger immediate increases in secondary control predicted steeper anxiety symptoms declines. Immediate shifts in proximal intervention "targets" may predict longer-term response to an SSI for youth internalizing distress. CLINICAL TRIALS: Clinicaltrials.gov registration: NCT03132298.
Keywords: Anxiety; Brief intervention; Depression; Mindset; Single-session intervention.