Exploring Candidate Mechanisms of Change of EMIcompass, a Novel, Transdiagnostic Ecological Momentary Intervention for Prevention and Early Intervention in Youth: Findings from a Secondary Analysis of an Exploratory Randomized Controlled Trial

Background: Ecological momentary interventions targeting transdiagnostic mechanisms are promising for prevention and early intervention, but evidence on their mechanisms of change is very limited.Objective: To explore indirect effects of EMIcompass, a transdiagnostic, compassion-focused ecological momentary intervention, on mental health outcomes (i.e., psychological distress, clinical symptoms, quality of life) via candidate mechanisms of change (i.e., stress reactivity, emotional reactivity, threat anticipation, resilience, and aberrant salience) in youth with early mental health problems. Methods: We conducted a secondary analysis of an exploratory, assessor-blind randomized controlled trial, in which youth aged 14–25 years with early mental health problems were randomly allocated to experimental (EMIcompass+treatment as usual [TAU]) or control condition (TAU). Data was collected before randomization, at post-intervention and at four-week follow-up. Results: N = 92 participants were recruited, of which n = 46 were allocated to the experimental condition. No signals of indirect effects of condition on any outcome through the five mechanisms (i.e., 95 % confidence intervals included zero) were found. The magnitude of association, however, indicated that the association between EMIcompass and psychological distress may be mediated via pathways through threat anticipation (β = -0.12, 95%CI = -0.30 – 0.03). Further, we observed associations between changes in candidate mechanisms and mental health outcomes.Conclusions: Although no direct signals of mediation via candidate mechanisms were observed due to lack of power, condition-linked shifts in our candidate mechanisms were associated with mental-health outcomes. Larger mechanism-powered trials are now required to delineate causal pathways and refine scalable prevention and early intervention strategies.