What is the placebo effect?


What is the placebo effect? 
The term placebo originated in the realm of medicine, but the discussion surrounding this phenomenon has extended to psychological treatment and research as well. The classic description of a placebo effect is an ‘inert’ treatment i.e. one that does not possess any active ingredients, that still somehow leads to improvements.
A common example is giving someone a pill made out of sugar instead of actual pain medicine. When you give someone this sugar pill you would not expect their pain to go away. Surprisingly however, taking such a placebo pill can in fact work, as multiple studies have indicated. Moreover, people don’t just subjectively feel better after receiving a placebo but they also improve on a physiological level for instance showing reductions in neural activity in brain areas that process pain.

The improvements that have been found as a result of receiving a placebo treatment are remarkable, but if a placebo is indeed ‘inert’.. how is it even possible for people to improve?

How can the placebo effect be explained? 
The discussion of the placebo effect has shifted over time from the classic example of ‘inert’ placebo pills to factors that ‘simulate active treatment’. In this context, various environmental and/or psychosocial factors have been proposed that may explain the placebo response.  

The placebo effect has most often been linked to people’s expectations. Specifically, if someone believes that a treatment will help them improve, then it is very likely that it actually does. Interestingly, the opposite effect has been found as well with negative outcomes (e.g. side-effects) being more likely to occur as a result of negative expectations. This phenomenon has been described as the nocebo effect.

Another factor that may play a role, one that is closely linked to people’s expectations, is the desire to obtain positive results or to avoid negative results.

Certain elements of a treatment may be associated with a certain meaning, and these associations may in turn influence treatment outcome. In one example, people either received blue pills or red pills with the exact same content. Interestingly, depressant effects were more commonly reported with the blue pills, whereas stimulant effects were reported with the red pills, likely due to certain colour assocations. 

Classical conditioning
Classical condition has also been tied to the placebo effect. In one example, patients were repeatedly given a flavoured drink whenever their immune suppression medication was administered. After a while, the flavoured drink itself was sufficient in causing the desired immune suppression effects.

What the placebo effect is NOT
Because the placebo effect has been described and explained in many different ways, it is important to clarify the difference between placebo and other concepts that may seem similar:

Natural history is a natural decline in symptoms, purely due to the passage of time.
Regression to the mean is when individuals with extreme scores on any measure at one point (e.g. the initial assessment) will have less extreme scores the next time that they are tested (closer to the average) for purely statistical reasons.

Further discussion
Although definitions and explanations for the placebo effect are varied and although individuals may differ in their susceptibility to the placebo effect, there is no doubt that the placebo effect is an important phenomenon to take into account in the development and assessment of interventions. In our upcoming blog posts we will discuss how we can control for or alternatively take advantage of placebo effects in our study designs and the development of our games. 


Sources and further reading 

Price, D. D., Finniss, D. G., & Benedetti, F. (2008). A comprehensive review of the placebo effect: recent advances and current thought. Annu. Rev. Psychol., 59, 565-590.

Kaptchuk, T. J., & Miller, F. G. (2015). Placebo effects in medicine. New England Journal of Medicine, 373(1), 8-9.

Moerman, D. E., & Jonas, W. B. (2002). Deconstructing the placebo effect and finding the meaning response. Annals of Internal medicine, 136(6), 471-476.

Bystad, M., Bystad, C., & Wynn, R. (2015). How can placebo effects best be applied in clinical practice? A narrative review. Psychology research and behavior management, 8, 41.

Colloca, L. (2014). Placebo, nocebo, and learning mechanisms. In Placebo (pp. 17-35). Springer, Berlin, Heidelberg.




Joanneke Weerdmeester

Researcher, psychologist, PhD-candidate, gamer, language enthusiast and lover of all things geeky.


More updates

Want to keep up-to-date with our research?