Who benefits from guided internet-based interventions? A systematic review of predictors and moderators of treatment outcome

Objective: To our knowledge, no systematic review or meta-analysis has been conducted on all predictors or moderators of treatment outcome across diagnoses in guided internet-based interventions (IBIs) for adults. We aimed to aggregate the results of relevant studies and identify research gaps. Methods: After duplicate removal, 1615 articles, identified by searching the databases PsycInfo, Ovid Medline, and Pubmed and through snowballing, were screened following detailed in- and exclusion criteria in April and May 2021. Risk of bias (QUIPS) and intra- and interrater reliability for screening and risk of bias were assessed. Variables were grouped and categorized, then synthesized using vote counting based on direction of effect. Results: N=50 articles were included in the review. Seventy-seven predictors or moderators were generated, of which adherence, baseline symptoms, education, age, and gender were most frequently assessed. Adherence, treatment credibility, working alliance, and baseline scores emerged as conclusive predictors/moderators. Results for other variables were mainly inconsistent or inconclusive. Conclusion: Our review highlights that it is currently difficult to predict, across diagnoses, who will benefit from guided IBIs. Further rigorous research is needed to identify predictors and moderators based on a sufficient number of studies. PROSPERO registration: CRD42021242305.