Development of a mobile health intervention for electronic cigarette use among young adults - PROJECT ABSTRACT Despite declines in combustible cigarette smoking among young adults, use of electronic nicotine delivery systems (ENDS), such as e-cigarettes, continues to rise. Young adulthood marks a particularly susceptible time for the experimentation and initiation of substance use behaviors, including tobacco. Further, some who initiate tobacco use with ENDS transition to combustible products, such as cigarettes or marijuana, or become users of multiple products (dual/poly users). Despite the addiction potential of ENDS and high interest in quitting among young adults , there are few resources available to help individuals quit or reduce their use of ENDS. The aim of the proposed research is to develop an evidence-based mobile health (mHealth) text- message based intervention for young adult ENDS and dual (ENDS and cigarette) users (K99 phase 1), and determine whether the intervention is effective in reducing ENDS use (primary outcome) and increasing cessation , quit attempts, and use of nicotine replacement therapy (NRT; secondary outcomes; R00 phase 2). In phase 1 (K99), we will determine intervention content and delivery schedule based on existing evidence- based smoking cessation materials as well as utilize focus groups with young adult ENDS users (both ENDS- only and dual users) to adapt content to an mHealth ENDS-specific intervention. We will then run an initial pilot study with 45 participants to determine intervention feasibility and acceptability. After the pilot intervention, we will conduct additional focus groups with individuals who participated in the pilot to further refine the intervention. In phase 2 (R00), we will conduct a randomized control trial to determine the intervention’s effect on ENDS outcomes. Young adult ENDS and dual users will be randomized to one of three conditions: 1) mHealth ENDS intervention, 2) standard ENDS advice+NRT, or 3) standard advice alone . Standard advice will include a website that will be updated with information on products/safety and strategies for ENDS cessation as information evolves over the course of the study. Participants in the mHealth condition will complete a 6- week text-message based intervention with content tailored based on 1) motivation to quit ENDS, 2) whether an individual uses ENDS only or is a dual user of tobacco products, and 3) target quit date. Participants will complete an assessment of ENDS behaviors, quit attempts, and use of NRT at 3-month follow-up. ENDS use frequency will be the primary outcome , while biochemically verified 7-day point prevalence abstinence, NRT use, and quit attempts will be the secondary outcomes of interest. This study’s findings will inform emerging ENDS intervention literature, an area where a clear evidence base is currently lacking, and whether a mHealth intervention can impact young adults’ ENDS cessation, behaviors, and barriers to NRT use. This project will serve to provide valuable mentorship and training complementary to the proposed research to facilitate Dr. Brett’s transition to an independently-funded investigator and clinical addiction and tobacco control scientist.