Tuesday, September 11, 2012

The placebo effect occurs at an unconscious level

One of the most peculiar treatment effects in medicine is that of a placebo. It is not supposed to work, but somehow patients receiving therapy based on a non-efficacious compound do seem to benefit from it. Placebos do not have any so-called bio-active components, and are often used for comparison with a 'real' drug. Nevertheless, the placebo effect is an interesting phenomenon and it tells us something about how the body itself facilitates and improves treatment. Many scientists have suggested that being aware of the fact that you are going to get treated adds to the placebo effect, but a recent study shows that patients do not have to be conscious about it for a placebo to work.

Scientists from the Beth Israel Deaconess Medical Center set up experiments to simulate treatment and study the effect on participants. The 'therapeutic' consisted of heat stimulation while the participants, forty in total, had to watch a computer screen. The scientists were showing the participants pictures of human faces that were either associated with low or high pain. Basically, this induced a placebo (low pain) or nocebo (high pain, a placebo with negative associations) effect. Participant-reported levels of pain were acquired in order to assess the response differences between equal levels of heat while being exposed to a placebo or nocebo. Thereafter, the experiments were repeated by again providing heat stimulation, but flashing the aforementioned faces so fast that it was impossible for the participants to discern whether they were dealing with the placebo or nocebo.

First of all, display of a face showing high levels of pain was associated with a higher participant-reported level of pain as a result from the heat. This basically shows the effect of a placebo; an effect that is not derived from a difference in treatment. While most of us would think that the placebo effect is something that a patient needs to experience consciously, as witnessed from the association with low and high pain faces, the second experiment with the flashing images points in a different direction. By flashing the images, which means the participants were unable to gain conscious awareness of the low and high pain display, the same difference in reported pain levels was observed.

The study shows that it is not likely that awareness helps to increase a treatment's efficacy. Instead, something on an unconscious level is affecting the outcome, but it is impossible to deduce from this study what that could be. The scientists argue that brain scanning techniques could be used in future studies in order to gain insights into the mechanisms that underlie the placebo, and corresponding nocebo, effect. It is known that conscious thought processes can affect bodily physiology, which is why it makes sense to think that a placebo effect is something that you need to be aware of. That is what makes this study particularly intriguing. It does remain questionable whether the results of this study can be extrapolated to double-blind placebo-controlled clinical trials, which are the golden standard for the development of new drugs.

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