Exploring cross-cultural effectiveness of internet-based depression treatment (IBAT-D) with peer-to-peer support vs. without across WEIRD and non-WEIRD samples: a research protocol for a randomized controlled trial.

Background
Internet-based self-help interventions (IBIs) have proven effective in reducing depression, especially in high and middle-income countries, and have proven to be flexible and location-independent. However, unguided IBIs often face high dropout rates, low uptake, lower adherence, and reduced effectiveness.Objective
This study evaluates the effectiveness of a self-help program against depressive symptoms (Deprexis) with or without peer-to-peer support, focusing on cultural differences between WEIRD (Western, Educated, Industrialized, Rich, and Democratic) and non-WEIRD countries, specifically Switzerland and India. Additionally, this research explores Deprexis's efficacy in French-speaking Switzerland, aiming to extend its benefits to this demographic. The study also investigates mood responses to monetary and social rewards using the Fribourg Reward Task to understand the relationship between depression and reward system dysfunction in a cross-cultural context.Methods
The study is a randomized controlled trial; participants with mild to moderate depression will be randomized into three groups of 80 each: Deprexis only, Deprexis with peer-to-peer support, and a control group on a waiting list. The intervention lasts 8 weeks, with measurements at baseline (T0), mid-intervention (4 weeks, T1), post-intervention (8 weeks, T2), and follow-up (3 months post-intervention, T3). Participants will complete online questionnaires on RedCap and the Fribourg Reward Task.Primary Outcome
depressive symptoms at 8 weeks post-intervention.Secondary Outcomes
mood responses to reward, pleasure, and social support, with moderators and mediators like anxiety, stress, quality of life, PTSD, childhood trauma, self-efficacy, and self-esteem.Results
The study, registered at ClinicalTrials.gov (NCT06480474) and Swiss National Clinical Trials (SNCTP000005917), was approved by the Ethics Committee of Vaud (CER-VD) in May 2024 (protocol date: 22.05.2024; version: 4; 2023-D0112). Recruitment began in June 2024 and is expected to end in May 2026.Conclusion
This study examines the potential of IBIs, including peer-to-peer support forums and the Deprexis program, in addressing depression globally. It investigates the extent to which cultural adaptations may be required in order to integrate globally available online mental health care into existing health systems to bridge treatment gaps and improve outcomes. Future research should explore these interventions' effectiveness in diverse cultural settings and their long-term impacts.