Placebo Effect: How Expectations Influence Treatments and Medical Research - Drauzio Varella Portal

The belief that a treatment will work sometimes actually makes it happen. Understand how the placebo effect works .

It's common to think that the only thing that can solve pain is medication or surgery. But there's another factor that greatly influences how we react to treatment: expectations. This is called the "placebo effect."

"We are animals whose experience and interaction with reality make all the difference, and the placebo effect has to do with this. Much of what happens in our bodies is influenced by what we anticipate about what will happen and other variables we don't even perceive," explains Fabiano Moulin, a neurologist and member of the Lifestyle Committee of the Brazilian Academy of Neurology (ABN).

The placebo effect, therefore, is nothing more than the natural functioning of a predictive brain like ours. Just going to a beautiful office, with professionals in lab coats and modern machines, the feeling regarding the consultation or the prescribed intervention already tends to be more positive. The patient feels better, even if there was no direct reason for it.

The placebo effect is fundamental in clinical research. In randomized clinical trials, neither the researchers nor the volunteers know who will receive the real intervention or the placebo—something similar to the treatment, which could be an inert pill, like a sugar pill.

"Let's imagine it's a pain medication. I give you a pill, which I also don't know if it's medicine or a placebo, and you tell me how severe your headache is on a scale of 0 to 10. Two hours later, you tell me it's down to a seven," explains Dr. Fabiano.

Based on this response, researchers compare how much the intervention reduced pain compared to the placebo group. In general, simply by taking the pill or receiving special attention, the patient usually reports a 50% reduction in pain. In the previous example, the placebo group reports a three-point improvement (from 10 to 7). Therefore, to determine whether the medication works, it needs to improve by four or more points. If it drops by just three, it's working the same way as the placebo.

"And that's not a problem, but we need to name things correctly. I can't say the medication is helping if, in fact, it's a placebo effect," the expert points out. "What the studies try to do is measure, beyond this effect of expectation and the predictive brain, how much the intervention actually helps or hinders," he continues.

The phenomenon is so intense that, even knowing they're receiving a placebo, the patient can feel better. A 2010 study of 80 patients with irritable bowel syndrome compared those who knew they were taking an ineffective pill with those who didn't receive treatment. After three weeks, symptom improvement was significantly greater in those taking the pills, even though they knew they had no physiological effect.

Complaints such as pain, allergies, or difficulty sleeping are those that benefit most from the placebo effect because they are directly linked to expectations and the interaction of the body and mind with the external environment.

However, it can only be used intentionally and legally in clinical research. In everyday life, ethical dilemmas arise, such as the breach of trust between doctor and patient if a placebo is prescribed without the patient's consent, and the progression of the disease when there is an effective treatment. The Federal Council of Medicine, therefore, prohibits the practice.

Furthermore, the nocebo effect can occur, when symptoms arise or intensify in response to a negative expectation, even if there is no real cause for it. This happens, for example, with a patient who expects to feel pain when going to the dentist: the risk of this sensation actually occurring is greater.

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