Non-inferiority margins for trials need to be meaningful: commentary on Flückiger et al. (2026)

Flückiger and colleagues discussed in their recent umbrella meta-analysis the use of non-inferiority margins for randomized controlled trials comparing bona fide psychological treatments. The review raises important points to increase the diversity of trial designs used in psychotherapy research and, together with the invited comments, provides a springboard for future methodological and standards development in the field. In our Commentary we focus on two questions: Firstly, we challenge whether the derived effect size can be used as a non-inferiority margin for the planning of future trials; and secondly, we highlight the importance of the contribution of other sources of information for the determination of target differences, and in particular that of including public and patient voices.