INTRODUCTION SUMMARY. Major depression in youth is a serious psychiatric illness with extensive acute and chronic morbidity and mortality. In 2018, the American Academy of Pediatrics released updated practice guidelines promoting screening of youth depression in primary care (PC) clinics across the country, representing a critical step towards increasing early depression detection. However, the challenge of bridging screening with service access remains. Even when diagnosed by PC providers, <50% of youth with elevated depressive symptoms access treatment of any kind. Thus, there is a need for interventions that are more feasible for youths and parents to access and complete—and that may strengthen parents’ likelihood of pursuing future, longer-term services for their child.Single-session interventions (SSIs) may offer a promising path toward these goals. SSIs include core elements of comprehensive, evidence-based treatments, but their brevity makes them easier to disseminate beyond traditional clinical settings. Indeed, SSIs can successfully treat youth psychopathology: In a meta-analysis of 50 randomized controlled trials, SSIs reduced youth mental health difficulties of multiple types (mean g=0.32). To date, one SSI has been shown to reduce youth depressive symptoms in multiple RCTs: the online “growth mindset” (GM) SSI, which teaches the belief that personal traits are malleable rather than fixed. As one example, a 30-minute GM-SSI led to significant 9-month MD symptom reductions in high-symptom youths ages 12-15 versus a supportive therapy control (N=96; ds=0.60, 0.32 per parent and youth reports). Thus, GM SSIs represents a scalable, evidence-based strategy for reducing youth depressive symptoms.GM-SSIs can also strengthen parent beliefs about the effectiveness of mental health treatment, which robustly predict whether youths ultimately access services. A recent RCT including 430 parents of youth ages 7-17 indicated that an online, 15-minute SSI teaching growth mindset of emotion (viewing emotions as malleable) significantly increased parents’ beliefs that psychotherapy could be effective, both for themselves (d=0.51) and their offspring (d=0.43), versus a psychoeducation control. By helping reverse parents’ low expectancies for treatment, this low-cost program may enhance parents’ odds of seeking services for children with mental health needs.Accordingly, this study will test whether empirically-supported GM-SSIs can help bridge the gap between PC-based depression screening and access to depression services for high-symptom youth. Youths reporting elevated internalizing symptoms at a PC visit will be randomly assigned to one of two conditions: Information, Psychoeducation, and Referral (IPR; i.e., usual care) or IPR enhanced with youth- and parent-directed online SSIs (IPR+SSI), designed to reduce youth internalizing symptoms and improve parents’ mental health treatment expectancies, respectively. We predict that (1) IPR+SSI will increase parents’ treatment-seeking behaviors, versus IPR alone, across 3-month follow-up; (2) IPR+SSI will reduce youth internalizing symptoms across 3-month follow-up versus IPR alone; (3) IPR+SSI will reduce parental stress and psychological distress across 3-month follow-up, versus IPR alone; (4) parents and youths will rate this service delivery model as acceptable.METHOD SUMMARY. Per youth-reported internalizing symptom elevations during a PC visit (score >=5 on the Pediatric Symptom Checklist internalizing subscale), eligible families (N=246; youth ages 11-16) will be invited to participate in the study. In online surveys, parents will self-report recent treatment-seeking behaviors, expectancies for psychotherapy, stress and psychological symptoms, and youth mental health problems, along with family and demographic information; youths will self-report symptom levels. Within the same survey, youths and parents will then be randomized (1:1 allocation ratio) to one of two experimental conditions (IPR+SSI or IPR alone); those assigned to IPR+SSI will complete an intervention feedback form immediately post-intervention. At 3-month follow-up, to assess SSI effects on parent treatment-seeking, parent stress and symptoms, and youth internalizing problems, participating youths and parents will complete the same questionnaires administered at baseline.SIGNIFICANCE. There is a need for novel, potent strategies to increase families’ access to youth mental health services following PC-based symptoms screening. Ideally, such strategies would be low-cost (e.g., those that do not require new staff); involve both parents and youths to address the myriad factors that may undermine service access; and impose minimal burdens on PC providers. Results will indicate whether one such strategy—providing online, low-cost SSIs to youths and parents—may help reduce youth internalizing symptoms and promote treatment-seeking in parents.