RESUMEN
BACKGROUND: Posttraumatic stress disorder (PTSD) and substance use disorder (SUD) co-occur frequently and have deleterious impact. Seeking Safety (SS) - an evidence-based, present-focused, coping skills model - lends itself to mobile app delivery. OBJECTIVES: A novel SS mobile app is compared to a control app that lacks the interactivity, social engagement, and feature-richness of the SS app. We hypothesized that the SS app would outperform the control on primary outcome variables (substance use, trauma symptoms) and at least two secondary variables. METHODS: Outpatients with current PTSD and SUD (n = 116) were randomized to the apps; assessed were pre, post (12 weeks), and 3-month follow-up in this online study. RESULTS: The SS app outperformed the control on the primary outcomes, but not on secondary outcomes. Also both conditions evidenced significant change over time from pre to post, with gains sustained at follow-up. External medication and supports during the trial did not differ by condition. CONCLUSION: This first RCT on a SS mobile app had positive results for reduction in substance use and trauma symptoms compared to a control app. This is noteworthy as mental health mobile apps, in general, evidence few positive outcomes. Our substance use finding is also notable as psychosocial interventions in PTSD/SUD populations find it harder to achieve reduction in SUD than trauma symptoms. Our control app may have represented too strong a comparison and weakened our ability to find results on secondary outcomes by condition.