The Placebo Effect Is Getting Stronger and Nobody Knows Why

I think most people understand the placebo effect in the vague, hand-wavy way that gets taught in high school biology. You give someone a sugar pill, they think it’s medicine, they feel better because of the belief rather than the pill. Simple.

What most people don’t know is that the placebo effect is genuinely one of the stranger and more unsettling things in modern medicine. It involves real physiological responses and not just imagined ones. Additionally, something has been happening with it over the past few decades that researchers are still actively arguing about. The short version is that in the United States specifically, placebos appear to be getting significantly stronger over time. Nobody has a fully satisfying explanation for why.

What the Placebo Effect Actually Is

When someone experiences a placebo effect, their body is producing measurable, physical responses. Studies using brain imaging have found that placebos activate the same neurobiological pathways that actual drugs use. Taking a fake painkiller can trigger the release of endorphins, the body’s natural opioids. Taking a fake Parkinson’s medication can cause genuine dopamine release in the brain. Sham surgeries, where patients are cut open and stitched back up with nothing actually done, have produced outcomes comparable to real surgeries in certain pain conditions.

The effect is also real enough that placebos work even when people know they’re taking a placebo. This is called open-label placebo, and it is deeply strange. Researchers tell patients explicitly that the pill contains no active ingredients, and a meaningful portion of them still improve. The working theory is that the ritual of taking a pill and expecting treatment sets off a conditioned response in the brain that doesn’t require deception to activate. Your brain is so used to associating the act of taking medicine with feeling better that it starts doing the work preemptively.

This is also why bigger pills tend to produce stronger placebo effects than smaller ones. Or why injections beat pills, and why elaborate clinical settings with lots of equipment and attentive doctors tend to amplify the effect considerably. Your brain is reading all the context around the treatment and drawing conclusions before anything has even happened.

The Study That Started the Conversation

In 2015, researchers at McGill University published an analysis of 84 clinical trials of pain medications conducted around the world between 1990 and 2013. What they found was genuinely surprising. The placebo response in those trials had been steadily increasing over that period. By 2013, patients taking fake pills were reporting about 30% less pain on average than patients taking fake pills had reported in 1990.

In 1996, real drugs relieved pain about 27% more than placebos in these trials. By 2013, that gap had shrunk to just 9%. The drugs weren’t getting weaker. The placebos were getting stronger.

Here’s the part that makes this genuinely weird: the effect was almost entirely isolated to trials conducted in the United States. Trials in Europe and elsewhere showed no comparable trend. Whatever was causing the increase, it was something specifically American.

The Theories

There are a few competing explanations and none of them fully closes the case.

The most cited one involves pharmaceutical advertising. The US and New Zealand are the only two countries in the world where drug companies are legally allowed to advertise prescription medications directly to consumers. Americans are bombarded with drug ads in a way that most of the world simply is not. The argument is that decades of advertising showing people going from visibly miserable to vibrantly happy after taking a pill has essentially conditioned Americans to believe very strongly in the power of medication. And because expectation is one of the primary drivers of the placebo effect, stronger expectation means stronger response.

There’s also an explanation that has less to do with culture and more to do with how clinical trials themselves changed over that same period. Trial regulations became significantly more rigorous in the US over those decades. Participants had to be consented more thoroughly. Researchers spent more time with them explaining the process. Longer, larger, more elaborate trials became more common, and longer trials with more contact with medical staff tend to produce bigger placebo responses because all of that attention and care is itself doing something.

A third possibility, raised by skeptics, is that the effect isn’t really about placebos at all. The argument goes that trial design changes made it harder to enroll the kind of participants who were very sick and therefore had lots of room to improve regardless of treatment.

Why This Actually Matters

The practical problem created by a stronger placebo effect is that it makes getting drugs approved significantly harder. The bar for a drug to be approved isn’t “does it help people.” It’s “does it help people more than a placebo.” If the placebo response keeps climbing, genuinely effective drugs can fail that comparison even when they’re working. There’s a real possibility that some medications that would help people are being shelved. Why? Well, because they couldn’t beat an increasingly powerful fake pill in an American clinical trial.

This is already showing up in pain research. In the past decade or so, around 90% of drugs for neuropathic and cancer pain failed to clear the clinical trial hurdle. Some of those failures are drugs that just didn’t work. But some researchers believe a portion of them were real treatments that couldn’t outperform an unusually robust placebo response.