Sertraline or placebo in chronic breathlessness? Lessons from placebo research

From the authors:
K. Pattinson and V. Wanigasekera raise important questions about understanding better the placebo response. This effectiveness study randomised people to either double-blind sertraline or placebo [1]. The study reported a response rate in the placebo arm (change in breathlessness now) almost mirroring that for sertraline. However, this observed change in the control group needs to be distinguished from any placebo response. There are at least two factors which are difficult to quantify but are likely to account for the vast majority of improved breathlessness that was seen in the control and intervention arms: the Hawthorne effect [2]; and regression to the mean [3]. Any placebo response is likely to be a very small component of the response rate in the placebo arm.