Beyond sham type: Comparator compatibility in meta-analyses of rTMS for major depression

Eren and Takım's meta-analysis found that prefrontal repetitive transcranial magnetic stimulation (rTMS) improved depressive outcomes, while sham type (coil tilt versus sham coil) was not a statistically significant moderator of the estimated treatment effect. The latter finding does not establish that the sham procedures are equivalent or interchangeable. Differences in residual cortical stimulation, sensory or peripheral stimulation, and blinding raise the question of whether studies grouped under these labels estimate sufficiently similar treatment contrasts. We propose a four-step Comparator-Compatibility Check (CCC): define the review question, describe the comparator as an intervention, identify features relevant to the treatment contrast, and assess robustness in prespecified comparator-informed analyses. The CCC links sham characteristics to the target treatment contrast and the choice and interpretation of robustness analyses. We illustrate potential analyses for Eren and Takım's review as a methodological proposal, not a completed reanalysis.