Credibility and expectancy associated with ultra‐brief and standard‐length digital treatments: A preliminary examination of impact on treatment outcome

OBJECTIVE: Ultra-brief treatments (i.e., three or fewer sessions/modules) are associated with reductions in depression and anxiety symptoms, though the mechanisms underlying their effects are unclear. Research has yet to compare how perceptions of treatment credibility and outcome expectancy (i.e., how suitable and effective the treatment will be) may differ between ultra-brief and standard-length digital treatments. METHODS: In a secondary analysis of a randomized controlled trial (N = 152), the current study examined the distribution of credibility and expectancy prior to receiving either an ultra-brief or standard-length digital transdiagnostic treatment based on cognitive behaviour therapy and explored whether these variables predicted improvement in anxiety or depression symptoms. RESULTS: There were no differences in how credible and effective participants perceived the two treatment options. In binary logistic regressions, higher credibility and expectancy were associated with greater odds of experiencing a clinically meaningful improvement (≥ 30% reduction) in anxiety (credibility OR = 1.68 [95% CI 1.15, 2.44]; expectancy OR = 1.50 [95% CI 1.11, 2.02]) and depression symptoms (credibility OR = 1.45 [95% CI 1.02, 2.05]; expectancy OR = 1.34 [95% CI 1.03, 1.76]) for the standard-length treatment only. The predictive value of these two variables diminished when they were entered into the models together, highlighting their conceptual overlap. Findings also indicated a potential moderating role for treatment preference. CONCLUSION: Credibility and expectancy predict treatment outcomes for standard-length digital treatment. Their influence on outcomes in ultra-brief digital treatment is unclear and further research with larger samples is warranted.