A Crowdsourced Megastudy of 12 Digital Single-Session Interventions for Depression in American Adults.

Digital self-guided single-session interventions (SSIs) provide a structured psychological intervention within one interaction. We crowdsourced 66 diverse 10-minute SSIs for depression and selected 11 for testing in a pre-registered "megastudy" (ClinicalTrials.gov ID: NCT06856668). American adults (N = 7,505) experiencing elevated depressive symptoms were recruited online and randomly assigned to one of the 11 crowdsourced SSIs, a previously-validated active comparison SSI, or a control without intervention content. Nearly all SSIs boosted agency and hope for improvement immediately after completion (ds ≤ 0.37). However, only two significantly reduced depression at four-week follow-up (ds = 0.14 and 0.15). Unexpectedly, some SSIs may have decreased readiness to change at four weeks (ds ≤ 0.14). The most successful SSIs provided focused, engaging, and actionable guidance on a skill that directly addressed users' struggles. Future work should aim to leverage SSIs' short-term gains to promote longer-term behavior change or service engagement.