Blinding success of rTMS applied to the dorsolateral prefrontal cortex in randomised sham-controlled trials: A systematic review

Abstract

Objectives. The lack of a suitable sham condition for repetitive transcranial magnetic stimulation (rTMS) research may compromise the success of blinding procedures. The aim of this systematic review was to examine the reporting of blinding success in randomised sham-controlled trials (RCTs) of rTMS applied to the dorsolateral prefrontal cortex. Methods. A literature search using Pubmed and Web of Science was conducted to identify RCTs of rTMS. Regression analyses were used to investigate whether participants in the real and sham rTMS groups differed in (1) their ability to correctly guess to which intervention they had been randomised, and (2) how likely they were to think they had received real rTMS. Results. Thirteen out of 96 (13.5%) RCTs reported blinding success. Available data from 9/13 studies showed that participants in real and sham rTMS groups were not significantly different in their ability to correctly guess their intervention allocation, but with a trend for participants in the real group to more often guess correctly. However, people in the real rTMS groups were significantly more likely to think they had received real rTMS compared with those in sham rTMS groups. Conclusions. Few RCTs in rTMS report on blinding success. As current sham methods may inadequately mimic real rTMS, this could result in only partial success of blinding and bias estimations of treatment effects.

Key words::

• Repetitive transcranial magnetic stimulation
• placebo effect
• double-blind study
• randomized controlled trial
• prefrontal cortex

Acknowledgements

This work is supported by the Biomedical Research Centre (BRC) for Mental Health, South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, King's College London, and by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research Scheme (RP-PG-0606-1043). The views expressed herein are not necessarily those of the NHS, the NIHR or Department of Health. Frederique Van den Eynde is a research fellow in the Marie Curie Research Training Network INTACT (MRTN-CT-2006-035988). Dr S. Guillaume is supported by a grant from l'Institut Servier, France. Emma-Louise Hanif is funded by an NIHR BRC PhD Studentship.

Statement of Interest

The authors have no conflict of interest with any commercial or other associations in connection with the submitted article.