About this Research Topic
The progress in understanding the underpinnings of placebo and nocebo effects across a number of conditions has revealed important information on the therapeutic action of words, rituals, expectations and beliefs. The positive context surrounding the administration of a placebo may prompt individuals to expect improvement and positive outcomes in terms of the placebo effect. Alternatively, a negative context, can lead individuals to expect a worsening of symptoms in which changes in the negative direction are registered as part of the nocebo effect.
In clinical trials, nocebo effects are best illustrated as the development of side effects in the placebo groups. As no active medication is administered in the placebo arm, the observed adverse events are not caused by the pharmacodynamic processes, but rather by the psychosocial factors surrounding treatments and patients. In these studies, patients know that they may receive an active treatment or a placebo and are accordingly informed by the investigator about the possible side effects they may experience after taking the active drug. This generates in subjects a negative expectancy that can lead to a negative outcome, in particular the appearance of specific side effects.
The development of side effects after placebo intake has been reported for several medical conditions. Many patients in the placebo groups of these clinical trials also discontinued the treatment because of symptoms that were attributed to the medication. Notably, the side effect profiles of placebo groups reflect the expected side effects of the drug, which also led to a similar rate of non‐adherence to treatment.
The extent of nocebo-related adverse events (AEs) in placebo-treated groups has been investigated in patients having neurological diseases such as Alzheimer disease, Parkinson’s disease, multiple sclerosis, epilepsy and in pain disorders such as neuropathic pain, fibromyalgia and migraine. Each study demonstrated that the experience of AEs and, consequently, the dropout rate during placebo treatments are common in these types of patients. Similar findings have been reported in clinical trials conducted in patients with major depression.
The nocebo effect has been also documented in paediatric clinical trials, however very few studies comparing nocebo-related adverse events in children or adolescents and adults have been conducted.
Up to now, the nature of AEs has been poorly understood, and existing theories require further empirical testing. In particular, the findings have not been compared across the various diseases.
The goal of this Research Topic is to present the contributions of different research groups to furnish further empirical testing, discussing the most recent developments, integrating the knowledge accumulated across different diseases, and inspiring improving far-reaching implications for clinical trial design and clinical practice and therapeutic settings. We therefore welcome empirical, theoretical and meta-analytical work involving both clinical and healthy human populations that advance our understanding of Nocebo Effects and their Influence on Clinical Trials and Practice.
Keywords: Randomized Controlled Trials, Placebo Groups, Adverse Events in Clinical Trials, Expectancy Theory, Nocebo Effects, Placebo Effects
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