(PS9-47) Unified Protocol Skills Usage as a Mechanism of Effectiveness in Reducing Suicidal Thinking in a Smartphone-based Ecological Momentary Intervention

Suicide risk is highest immediately after discharge from inpatient psychiatric care (Chung et al., 2017), highlighting challenges in the transition to outpatient life and potential gaps in understanding how inpatient treatments function post-discharge. Identifying the specific aspects of interventions that drive symptom improvement can potentially enhance treatment effectiveness. Prior research has shown that CBT skills usage mediates change in psychotherapeutic interventions, suggesting its potential effectiveness for individuals experiencing suicidality (Domhardt et al., 2021). Cognitive behavioral protocols, such as the transdiagnostic Unified Protocol (UP), have demonstrated feasibility and acceptability for treatment of suicidal thoughts and behaviors, specifically in inpatient settings (Bentley et al., 2020; Diefenbach et al., 2021; LaCroix et al., 2018). However, no studies have examined cognitive skills as mechanisms of effectiveness in a smartphone-augmented CBT-informed treatment, presenting a critical gap in the literature. Smartphone interventions offer a scalable, individualized approach to delivering evidence-based treatments and supporting mental health, particularly for at-risk individuals (Melia et al., 2020). Despite existing research on intervention mechanisms, little is known about the uptake and effectiveness of UP cognitive skills in reducing suicidal thinking during the high-risk post-discharge period. This study aims to address this gap by evaluating UP cognitive skills as mechanisms of effectiveness in reducing suicidal ideation within a sample of suicidal psychiatric inpatients. Using ecological momentary intervention (EMI), the study will deliver UP-based therapeutic content, enabling real-time skills practice and momentary assessment of suicidal thinking before and after each exercise practice. Analyses will examine whether improvements in UP cognitive skills usage mediate reductions in suicidal thoughts and behaviors and whether enhanced skill usage predicts greater effectiveness. Specifically, we will examine a model predicting average slope, for each participant, each week of the pre- to post-exercise practice ratings of suicidal thinking will be predicted by weekly assessments of UP cognitive skills usage.