A new look at the placebo effect

Researchers at the University of Bristol’s School of Biological Sciences have developed mathematical models of the placebo effect to analyze the trade-off between the burden on the body and the benefits of triggering an immune response when needed.

The work is based on an idea expressed by the theoretical psychologist Professor Nicholas Humphrey. He suggested that due to the uncertainty of the situation in the outside world (for example, the possibility of starvation), the best option for the body may be for the immune system to work “not at full strength.” At the same time, any signals indicating the possibility of change may affect the level of the immune response.

In other words, constantly maintaining the maximum activity of the immune system can deplete the body’s energy reserves, so if the infection is not life-threatening, it is advisable to wait until we receive confirmation that the fight against it itself will not be more bitter than the disease.

This idea is based on animal observations. For example, Siberian hamsters practically do not fight infections if the lighting of their cage corresponds to the winter period: short days and long nights. Changing the lighting mode to summer leads to the launch of a full-fledged immune response in animals.

According to Humphrey’s theory, animals subconsciously trigger an immune response as a reaction to a long daylight period corresponding to a food-rich summer period. People also subconsciously respond to treatment, even fictitious ones, because they are convinced that it will weaken the infection, allowing the immune system to quickly deal with it without additional energy costs.

The developed models go even further and demonstrate that the placebo effect is modulated by the patient’s expectations. Earlier studies, which measured brain activity using functional magnetic resonance imaging (FMRI), demonstrated the relationship between the placebo effect and the activity of regions of the brain responsible for expectations. This pattern is an experimental proof of the validity of theoretical models.

The models show why changes in the perception of the value of recovery and good health or the importance of external factors can induce a placebo effect.

Now that the theoretical approach of the Bristol scientists has laid the foundations for understanding the placebo effect, further empirical work will help us figure out how to activate and manage this effect in a clinical setting. The data obtained clearly indicate that in the future, when conducting clinical trials under placebo control, special attention should be paid to the nature of the patient’s hopes for treatment, and not just to find out the benefits or uselessness of therapy. A better understanding of the placebo effect can completely change the norms of professional behavior of medical professionals and save a huge number of lives.

An article by Pete C. Trimmer et al. Understanding the placebo effect from an evolutionary perspective is published in the journal Evolution and Human Behavior.

Evgeniya Ryabtseva
Eternal Youth Portal http://vechnayamolodost.ru based on the materials of the University of Bristol: New insights into placebo effect.