Placebos work without the knowledge of the patient

Placebo: Mock treatments can also work unconsciously

12/09/2012

The body seems to be outsmarting on the subconscious level, as researchers from Harvard Medical School discovered. Nevertheless, if patients are unaware of a placebo treatment, pain relieving effects can be observed. Researchers sent hidden signals that activated the organism.

Research on the placebo effect has been controversial for decades. Above all, natural medicine is assumed by conventional medicine, most of the remedies only work because the patient expects a healing or analgesic effect. US scientists the „Harvard Medical School“ and other research institutions have changed the effects of placebo´s looked at more closely. They considered whether, for example, a verbalized assumption leads to the analgesic effect or whether other mechanisms play a role.

Unconscious acceptance or verbalized information
Common theories of the human placebo effect are based on the assumption that verbalized information, conscious perceptions, or various classical conditioning stimuli activate the placebo effect. As a rule, the placebo effect works when a doctor has previously signaled that the administered remedy helps.

A patient comes to the doctor and complains of abdominal pain. After a thorough examination, the doctor can not find any organic findings and diagnoses a functional abdominal pain. The family doctor gives the patient a pill, which, however, contains no detectable active ingredient. Nevertheless, the doctor leaves the patient on the assumption that it is a preparation for abdominal pain. The patient feels less or no pain after taking it because he expects the tablet to help. However, more and more research indicates that „the behavior may be triggered by stimuli outside of conscious perception previously“.

Only a part did not know about the placebo
To corroborate this assumption, Harvard University Medical Faculty researchers studied signals and stimuli in terms of expectations during research. The authors write in the scientific journal Proceedings of the National Academy of Sciences, „some of the subjects did not know that they were receiving only apparent treatment. Nevertheless, the placebo worked“.

The study involved 40 healthy young women and men (24 women, 16 men, mean age 23 years). At the beginning of the experiment, all participants learned to cognitively associate a specific facial expression on a screen with a painful heat attack. Another facial expression, however, was painless. Depending on which image was shown in the training session, a thermo-probe attached to the participants' left forearm hurt more or less. On a scale of 0 to 100, subjects should note how severe the pain on their arm was.

Unconscious level controlled signal stimuli
In the second study the participants were shown the same different faces. However, the subjects did not know that the heat irritation remained the same. In the first part of the experiment, the faces were displayed for 100 milliseconds each. With this time period, the subjects were able to recognize the different faces on the conscious level. In the second round, the researchers showed the images only for about 12 milliseconds each.

„None of the participants could consciously recognize or distinguish the faces“, explained the research team. Nevertheless, the subjects always rated the stimulus as painful when „the image cognitively associated with the unpleasant pain was displayed in the foreground“. Conversely, the image was as „pleasantly noted when the face flared that was associated with a harmless heat irritation“. That happened, „regardless of whether the study participants had consciously recognized the picture or not“.

New findings on the placebo effect
As a result, the results could be „a whole new door to understanding the placebos and the rituals of medicine“ study director Ted Kaptchuk from Harvard Medical School. The newly discovered mechanism „works automated, fast and is independent of conscious considerations and reviews“, summarizes Kaptchuk.

According to the scientists, the new findings are valuable for doctors, patients and clinical trials. "Without being aware, the patient apparently also registers subtle messages that, for example, the doctor sends out," the authors write. Thus, it could also be explained why even unspoken expectancies on the part of the physician to a drug or therapy can have a positive effect on the patient's effect. (Sb)

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