Pharma & Healthcare

Why Is The Placebo Effect Exploding In The U.S. But Nowhere Else?

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The placebo effect is getting stronger – but only in the United States. That’s the finding of new research that analyzed the results of 84 clinical drug trials from 1990 to 2013 for medications prescribed to treat chronic pain.

The research team from McGill University in Montreal found that during the 23-year timeframe, pain inhibition from the placebo effect showed a dramatic increase, which is to say that pain experienced by patients in the clinical trials dramatically decreased. By 2013, patients receiving placebos experienced 30% decreased pain levels on average.

Those results are intriguing on their own, but what’s odder is that they only held true for drug trials conducted entirely in the U.S. Similar trials conducted in Europe and Asia showed no changes in the placebo effect over the same time period.

As a quick refresher, we’ve known that the placebo effect is especially acute for pain drugs ever since Henry Beecher, a soon-to-be famous anesthesiologist and medical ethicist, ran out of morphine to treat injured soldiers during World War II. Instead of telling his patients he couldn’t help them, he continued telling them he was administering morphine but was really injecting them with saline solution. To his amazement, 40% of the soldiers reported feeling less pain.

Since then, the placebo effect has held up across an expanse of research, including relatively recent and controversial studies on antidepressants and other psychiatric meds, reinforcing Beecher’s finding that the mere expectation of relief can trigger a physiological response.

But why does the placebo effect appear to be increasing only in the U.S., at least for chronic neuropathic pain meds?

The study’s authors offer a few possible explanations. First, both the size and duration of clinical drug trials in the U.S. have increased over the last couple of decades. In 1990, the average drug trial included 50 or fewer patients and lasted about four weeks. In 2013, the same type of trial included more than 700 patients and lasted 12 weeks. These increases aren’t true of drug trials in many other countries.

For reasons that are still murky, it seems the longer a trial goes on—and the more people participate—the more pronounced the placebo effect. According to Jeffrey Mogil, Professor of Pain Studies at McGill and lead author of the paper, “The data suggest that longer and larger trials are associated with bigger placebo responses."

And what happens when the placebo effect blows up in a drug trial? "This, in turn, tends to result in the failure of those trials, since it makes it harder for pharmaceutical companies to prove that the drug being tested is more effective than treatment with a placebo," said Mogil.

A similar increase in the placebo effect has been observed in antidepressant drug trials, but those results aren’t exclusive to the U.S., which adds to the strangeness.

One other major distinction between the U.S. and almost every other country in the world may contribute to an exploding placebo effect: direct-to-consumer drug advertising. We’re the only country aside from New Zealand that allows drug companies to peddle their wares directly to consumers, and if you watch any TV at all you know that drug ads are ubiquitous (interestingly, these ads only became legal in the U.S. in 1997). While a difficult hypothesis to test, it’s plausible that all that exposure to sharply crafted advertising messages about a given drug’s effects may prompt a placebo response in some patients.

Whatever the causes (and there are almost certainly more than one), the U.S. appears to hold the title of reigning placebo nation.

The study was published in the journal Pain.
