PROJECT SUMMARY / ABSTRACT Justice-involved youth exhibit high rates of substance use and mental health symptoms, yet few receive treatment during detention or community re-entry. Once released into the community, caregivers must facilitate youth's treatment engagement, mobilizing significant resources and facing many barriers (e.g., transportation, mistrust) to do so. Parenting stress, which is heightened during youth detention and community reentry, is associated with greater perceived barriers to treatment, less youth therapeutic change throughout treatment, and premature treatment dropout. Addressing parenting stress improves youth treatment engagement and outcomes among youth exhibiting antisocial behavior, yet given the many barriers to treatment, novel approaches to intervention are needed; mobile health (mHealth) technology is one promising approach. Caregivers of justice-involved youth and system stakeholders are interested in mHealth treatment and mHealth addresses instrumental barriers (e.g., transportation) to treatment. Advances in technology and community engaged research allow for active stakeholder collaboration in mHealth application development, with no technological expertise required, through participatory informatics; caregiver involvement increases the likelihood the intervention will be relevant and efficacious. The purpose of this mixed-methods K23 study is to 1) develop a mHealth parenting stress intervention using participatory informatics; 2) assess the feasibility and acceptability of the participatory informatics approach and the intervention; 3) evaluate the intervention's preliminary efficacy in reducing parenting stress and increasing youth engagement in substance use or dual diagnosis treatment post-detention through a pilot RCT; and 4) understand systems-level factors that could influence eventual system adoption and sustainability. The overall goal of this K23 application is to provide protected, mentored time to expand Dr. Johanna Folk's (PI) capacities as an independent substance use health services researcher with expertise using participatory research methods to develop and evaluate novel interventions to engage justice-involved youth and families into youth substance use treatment. Dr. Folk will work with a team of experienced and knowledgeable mentors (Drs. Tolou-Shams, Aguilera, Knight, Arevian, and Chaplin) to increase her competency in: 1) substance use services research; 2) participatory research methods; and 3) mHealth methodology. The proposed research study is a logical extension of Dr. Folk's program of research to date which has spanned the developmental spectrum and focused on the complex interplay between justice involvement, substance use, mental health, and interpersonal relationships. This early career development award will provide the necessary candidate training and foundation for a larger R01 hybrid design clinical trial testing the efficacy of the mHealth parenting stress intervention de...