Wishful Thinking: The Power of Placebo

Could sugar pills have the power to heal? Margot Webster investigates whether there’s more to placebos than we once thought.

Written by: Margot Webster

Art by: Cheng-Yu (Kou) Huang


Homeopathy has long been at the forefront of a decade-long war between advocates of alternative medicines and science-based medicine. It has been established many times to be no more effective than a placebo in controlled clinical trials. The extent to which the original ingredients are diluted means that not a single molecule of any active substance could remain in homeopathic doses. Nevertheless, homeopathy is a billion-dollar industry and millions of people worldwide use these treatments regularly. Crucially, just because it works no better than a placebo doesn’t mean it doesn’t work.

The placebo effect is a psychological response, whereby doing anything that is perceived as helpful (like taking a sugar pill) against a condition will produce some improvement. The strength of this phenomenon crucially depends on how strong or powerful the medical intervention is perceived to be. Red sugar pills are more effective than white sugar pills, and intravenous injections of salt water are more effective than sugar tablets.

Because placebos contain no active ingredient and are accordingly incapable of triggering any biochemical changes in the body, the placebo effect is attributed to a change in our subjective perception. Their effectiveness can also be accounted for by a principle called ‘regression to the mean’: health has a natural tendency to fluctuate above and below an average. Because people seek treatments when their health is below the mean, they would have probably gotten better anyway, with or without any intervention. This theory obviously applies to minor transient changes in health only, as no one would expect someone diagnosed with terminal lung cancer to get better naturally. Fortunately no one is seriously suggesting placebos to treat terminal cancer.

However, the placebo effect may be more than a simple illusory shift in our perception, and could create physical, measurable changes in our bodies under certain conditions. Just like Pavlov’s dog learned to salivate at the sound of a bell because it had become so strongly associated with the provision of food, so a placebo may trigger real biochemical changes when associated with a real treatment through conditional learning. At least, this is what a 2016 study working with Parkinson’s patients seems to suggest. Parkinson’s disease is a neurological motor disorder caused by the loss of a specific population of neurons that secrete dopamine. Researchers gave patients a placebo together with their normal treatment: a drug that works by raising dopamine levels. After extensive training, the placebo was so strongly associated with the improvement caused by the real drug that the placebo alone could raise dopamine levels in the brains of Parkinson’s patients.

Although it has been shown repeatedly that placebos can have powerful effects while greatly reducing costs and harmful secondary effects, modern medicine is still reluctant to adopt them. The main argument against their use is an ethical one. Is it justifiable for medical professionals to use any means necessary to improve the chances of a patient’s recovery, or does the patient’s right to be fully informed about their treatment override all else?

It is often assumed that subjects must believe they are taking a real treatment for the placebo effect to come into action. However, some studies have suggested that open-label placebos clearly presented as containing no active substance can still be effective in conditions such as irritable bowel syndrome and chronic back pain, alleviating the need for doctors to deceive their patients. This is probably due to the fact that although subjects know these treatments contain no active substance, they still believe that they can work.

Although impressive, these results do not mean that placebos could, or should, replace pharmacologically active medical treatments that have been proven to work.  However, they may be helpful in conjunction with active drugs to reduce dosage and side effects, and for illnesses where current treatments are still not very effective, such as chronic back pain. Such results seem to indicate that patients’ expectations have an important role to play in their recovery. Perhaps then, modern medicine should consider the implications that this may have for doctor-patient relationships.

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