Placebos: The Effectiveness of Deception

A placebo is a substance or treatment that has no impact - negative or positive - on the health of the person subject to it. Its common forms are sugar pills, saline solutions, and sterile water, but a placebo could be any form of medical treatment that seems real.

The placebo effect occurs when a person who is being ‘treated’ with the placebo has responses or shows side effects to the treatment. This effect can occur regardless of whether that patient knows their treatment is a placebo or not, though it is more common when they are under the belief that the placebo is an actual medication or procedure. Placebos can induce physical changes such as an increase in heart rate and blood pressure, but are most powerful in illnesses that rely on self-reported symptoms such as depression, anxiety, or chronic pain.

Many cases of the placebo effect can be chalked up to simple coincidence. Some illnesses, like the common cold, get resolved quickly by the body’s immune system, regardless of whether a placebo is involved or not. Disorders like multiple sclerosis have remissive periods, where symptoms either weaken or vanish temporarily; a remission coinciding with a placebo injection or ingestion might make it seem as though the placebo has caused the symptoms to weaken.

Yet some people experience actual changes to their physical - and more commonly, emotional - health. This response to placebos is often attributed to the expectation effect. If the patient strongly believes in the treatment, their thoughts can cause temporary physical changes to the brain or body. An expectation of positive results can lead to a drop in the stress hormone cortisol, or misidentified symptoms. For instance, a patient taking a placebo may perceive a sharp pain as only an uncomfortable tingling. On the other hand, if the patient expects negative results, they will experience the expected negative side effects. In one study, subjects took placebo opioids and began showing symptoms of respiratory depression, which is a common side effect of opioids, despite the placebos not having any substance that would have caused such symptoms.

So just how strong is the placebo effect? Though it is impossible to measure accurately, in the United States the placebo effect is becoming stronger as time goes by. In 1996, drugs relieved pain 27% more effectively than placebos, but by 2013, drugs were only 9% more effective. A common theory is that as public trust in medical advancements grow, the more power the placebos have. As a society, our expectations regarding the efficacy and potency of certain medications is increasing; in turn, the power of the expectation effect increases. Another possible cause is the increase in trial length and size. Since 1990, the average trial length has increased from four weeks to twelve, and the size has increased from fewer than 50 subjects to over 500. Yet due to the unpredictable nature of the placebo effect, there is no confirmed reason as to why the placebo effect is getting stronger over the years.