Abstract
BACKGROUND: Loneliness is a significant public health concern with no established first-line intervention although modular, transdiagnostic, cognitive-behavioral interventions, such as the Unified Protocol (UP), are promising candidates. The UP contains skill modules to target anxiety, depression, and related conditions, although it is unclear if the UP can reduce loneliness and if UP skill use contributes to these reductions. METHODS: Using data from the first-stage randomization of a sequential multiple assignment randomized trial, we tested whether the UP led to reductions in loneliness and whether specific dimensions of UP skill use predicted session-to-session changes in loneliness. Participants (N = 70; M(age) = 33.74, 67% female, 74% white) completed six sessions of core UP modules, reporting how frequently they felt lonely and used UP skills before each session. Using hierarchical linear modeling, we examined the trajectory of change in loneliness and disaggregated between- from within-person variability to test session-to-session effects of skill use. RESULTS: Loneliness significantly decreased during treatment with the UP. Using more UP skills than one's personal average, but not frequency of skill use, predicted session-to-session decreases in loneliness. CONCLUSIONS: Therapists may be encouraged to guide patients toward using a large quantity of different skills to specifically address loneliness.