Why Do Placebos Work?

If you have a headache and take a pill, you’ll probably feel better. If that pill is a pain killer, great. But if it’s not, you might still feel the effects. That’s because humans respond well to treatment of any kind, from a doctor’s kind word to a sugar pill. One researcher, Harvard’s Ted Kaptchuk, is trying to figure out just why the placebo effect works. Harvard Magazine writes that while placebos can’t cure cancer, they can make people feel better:

But researchers have found that placebo treatments—interventions with no active drug ingredients—can stimulate real physiological responses, from changes in heart rate and blood pressure to chemical activity in the brain, in cases involving pain, depression, anxiety, fatigue, and even some symptoms of Parkinson’s.

Several studies have seen that patients in the study control groups—those who aren’t getting any treatment but are being told they are—see some results. They feel better. These control groups are important for understanding whether or not a treatment really works, or whether it’s simply piggy-backing on a placebo effect. But Kaptchuk felt a little bad lying to patients, so he did a different study:

His team again compared two groups of IBS sufferers. One group received no treatment. The other patients were told they’d be taking fake, inert drugs (delivered in bottles labeled “placebo pills”) and told also that placebos often have healing effects.

The study’s results shocked the investigators themselves: even patients who knew they were taking placebos described real improvement, reporting twice as much symptom relief as the no-treatment group. That’s a difference so significant, says Kaptchuk, it’s comparable to the improvement seen in trials for the best real IBS drugs.

And as drugs get better, placebos seem to as well. In 2009, Wired wrote:

Two comprehensive analyses of antidepressant trials have uncovered a dramatic increase in placebo response since the 1980s. One estimated that the so-called effect size (a measure of statistical significance) in placebo groups had nearly doubled over that time.

It’s not that the old meds are getting weaker, drug developers say. It’s as if the placebo effect is somehow getting stronger.

Wired also gives us the first documented case of the placebo effect:

The roots of the placebo problem can be traced to a lie told by an Army nurse during World War II as Allied forces stormed the beaches of southern Italy. The nurse was assisting an anesthetist named Henry Beecher, who was tending to US troops under heavy German bombardment. When the morphine supply ran low, the nurse assured a wounded soldier that he was getting a shot of potent painkiller, though her syringe contained only salt water. Amazingly, the bogus injection relieved the soldier’s agony and prevented the onset of shock.

Understanding and using the placebo effect can help doctors. Nearly half of doctors in a 2007 study admit to prescribing patients with drugs that they knew wouldn’t help them, or giving patients doses that were far too low to be useful, simply to get the patient to feel better. Kaptchuk, at Harvard, wants to understand why:

Those findings led to the team’s most recent work: imaging the brains of physicians while they treat patients—a side of the treatment equation that no one had previously examined. (The researchers constructed an elaborate set-up in which the doctors lay in fMRI machines specially equipped to enable them both to see their patients outside the machine and administer what they thought was a nerve-stimulating treatment.) “Doctors give subtle cues to their patients that neither may be aware of,” Kaptchuk explains. “They are a key ingredient in the ritual of medicine.” The hope is that the new brain scans will reveal how doctors’ unconscious thought figures into the treatment recipe.

So you might be getting a placebo at the doctor, but it doesn’t really matter because it might make you feel better.

More from Smithsonian.com:

Sugar Placebo Pills Can Make You Feel Worse

Rose Eveleth | | READ MORE

Rose Eveleth was a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.