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Nocebo as a potential confounding factor in clinical trials for Parkinson's disease treatment: a meta‐analysis
Author(s) -
Stathis P.,
Smpiliris M.,
Konitsiotis S.,
Mitsikostas D. D.
Publication year - 2013
Publication title -
european journal of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 124
eISSN - 1468-1331
pISSN - 1351-5101
DOI - 10.1111/ene.12014
Subject(s) - medicine , nocebo , placebo , randomized controlled trial , adverse effect , nocebo effect , meta analysis , confounding , population , clinical trial , alternative medicine , environmental health , pathology
Background and purpose Nocebo refers to adverse events ( AE s) generated by patient's negative expectations that medical treatment will likely harm instead of heal and can be assessed in placebo‐controlled randomized controlled trials ( RCT s). We examined AE s following placebo administration in RCT s for Parkinson's disease ( PD ). Methods After a systematic Medline search for RCT s for PD pharmacologic treatments published between 2000 and 2010, we assessed percentages of placebo‐treated patients reporting at least one AE or discontinuing due to placebo intolerance and searched for factors influencing nocebo's extent. Results Data were extracted from 41 RCT s fulfilling search criteria. Of 3544 placebo‐treated patients, 64.7% (95% CI : 53.6–74.4) reported at least one AE and 8.8% (95% CI : 6.8–11.5) discontinued placebo treatment due to intolerance. The number of AE s per 100 person‐months was 25.9 (95% CI : 16.8–39.8). Nocebo dropout rate was positively related to study population size and year of publication. Increased number of AE s per 100 person‐months was negatively correlated with the duration of treatment. AE rates, dropout rates, and AE s per 100 person‐months in placebo‐ and active drug‐treated patients were strongly correlated ( r = 0.941, 0.695, and 0.824, respectively). Conclusions Our analysis indicates a significant dropout rate related to nocebo in trials for PD treatment. Adherence and efficacy may be adversely affected with additional implications for clinical practice.