The role of placebo effects in itch-treatment of patients with skin disease
Placebo effects seem to have a considerable role in the treatment of itch in patients with common skin diseases (e.g. eczema or psoriasis). Dr. Antoinette van Laarhoven (Health, Medical and Neuropsychology) and colleagues have published these findings in the Journal of Investigative Dermatology, the top journal within the category of Dermatology.
Itch is the primary symptom of many highly prevalent skin diseases, such as eczema, psoriasis or chronic idiopathic urticaria. About 14-17% of the general population suffers from chronic itch, in other words: many people would benefit from improved treatment of itch symptoms. Patients often perceive chronic itch as very burdensome and it affects their quality of life; they frequently experience severe sleep problems, feel depressed, and increasingly withdraw from social activities and work. Treatments for chronic itch mainly include ointments and medication, for which effects are moderate.
Although placebo contributes to the effects of treatment for various symptoms and conditions, its effect on itch has rarely been investigated. This seems surprising, since previous studies have shown that itch seems to be highly susceptible to suggestion, illustrated by its “contagiousness” when talking about itch or watching others scratching. Therefore, Dr. Antoinette van Laarhoven and colleagues have conducted a meta-analysis investigating the role of placebo effects in the treatment of itch in patients with itch due to chronic skin disease. For their analysis they have included 34 articles from a systematic search of almost 12,000 articles. Studies describing clinical trials that included patients with chronic itch due to atopic dermatitis, psoriasis, or chronic idiopathic urticaria, were selected to investigate the magnitude of the placebo effect on itch. The levels of itch within the placebo control conditions were analysed by comparing the baseline levels of itch with those after placebo treatment. They found that itch was significantly decreased by 24% after placebo treatment.
Although the influence of other factors such as regression to the mean or natural course of disease cannot be excluded, the results indicate that placebo effects have a considerable role in the treatment of itch in patients with common skin diseases. Current findings might even underestimate the role placebo effects in itch-treatment since in the control conditions of clinical trials, placebo effects are minimized as much as possible. In clinical practice, maximizing placebo effects by optimizing patients' expectations can lead to improved treatment outcomes. Reduction of itch symptoms in patients with skin disease can lead to a reduced burden and improved quality of life of many patients.
This study is part of the NWO Vidi grant of Prof. Dr. Andrea Evers.