Nocebo in chronic inflammatory demyelinating polyneuropathy; a systematic review and meta-analysis of placebo-controlled clinical trials.

INTRODUCTION: Nocebo is very prevalent among neurological disorders, resulting in low adherence and treatment outcome. We sought to examine the adverse events (AE) following placebo administration in placebo-controlled randomized clinical trials (RCTs) for chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS: After a systematic literature search for RCTs for CIDP pharmacotherapy treatments, we assessed the number of AE in the placebo groups and the number discontinuations because of placebo intolerance.

RESULTS: Our literature search strategy revealed 82 papers. Data were extracted from three RCTs fulfilling our inclusion criteria. Approximately two in five placebo-treated patients (42.0%) reported at least one AE and approximately one in fifty placebo-treated patients discontinued placebo treatment because of AEs (2.1%). All patients participating in the CIDP trials reported similar AEs independently of the study arm they belonged.

CONCLUSION: Compared to other neurological diseases the nocebo effect in CIDP is significantly smaller.