Open-label placebos for wound healing: a randomised controlled trial

Abstract

Background. Open placebos are a novel treatment option, in which participants take placebos with full knowledge that they do not contain active medicine but instead work through psychological mechanisms. They are an ethical treatment option for harnessing placebo benefits, as they can be provided with full patient knowledge, without deception. Open placebo treatments have been shown to result in self-reported symptom improvements in irritable bowel syndrome (Kaptchuk et al., 2010) and chronic pain (Carvalho et al., 2016). No studies to date have tested the efficacy of open placebo treatments for objectively measurable physiological outcomes. Wound healing is an objectively measurable outcome that may benefit from open placebo treatment, as it is responsive to other psychological interventions such as relaxation (Broadbent et al., 2012) or emotional disclosure (Koschwanez et al., 2013; Weinman, Ebrecht, Scott, Walburn, & Dyson, 2008). Aim. The aim of the current study was to determine whether open placebo treatment improves the rate of punch biopsy wound healing. Methods. The study was designed as a single-blind randomised controlled trial. 70 healthy participants were given information about the placebo effect to establish an expectation that open placebo treatment would accelerate wound healing, and given a 4 mm punch biopsy wound under local anaesthetic by a dermatologist. Participants were then allocated to either an open placebo treatment condition or a no treatment control condition. The open placebo group took two placebo tablets twice a day for ten days. The principal investigator followed up with participants 7 days and 10 days later to photograph the wound. Healing was determined by the dermatologist from the photographs, based on reepithelialization of the wound surface. Questionnaires were administered to determine if there were any group differences in demographics, health behaviours or placeborelated expectations at baseline and at the 10-day follow up. We hypothesised that at 7 days and 10 days after receiving the wound, more participants in the open placebo condition would have fully healed wounds than in the control condition. In addition, at 7 and 10 days after receiving the wound, the percentage area of the wound surface reepithelialized would be higher in the open placebo than the control group. Findings. No significant differences were observed between treatment conditions for the number of participants with fully healed wounds at 7 and 10 days after wounding, nor for percentage area of the wound surface healed at 7 and 10 days. No other significant differences were found between groups for any questionnaire responses. Conclusion. Open placebo treatment does not improve the healing rate of punch biopsy wounds. Possible explanations are that either there are no physiological mediators between the psychological intervention of open placebo treatment and the desired outcome, participant expectations were not high enough to have an effect, the treatment duration was not long enough or did not start early enough to result in changes, or that only a small subset of participants responded to open placebos with accelerated wound healing. Open placebo treatments may help alleviate subjective symptoms but are unlikely to improve objectively measurable outcomes.