About 100 million Americans are currently dealing with chronic pain — approximately 70% of them are women . So now is really not a great time for our clinical trials of new pain medication to be failing more often. But, that's exactly what's happening. And new research suggests it may be because we're increasingly falling prey to the placebo effect.For the study , published online recently in the journal Pain, researchers combed through data from over two decades' worth of clinical trials. All 80 trials they found dealt with pain medication and were conducted in either the U.S., Europe, or Asia.First, the results showed that, as many have speculated, our placebo response is indeed getting stronger. And, because one measure of a drug's effectiveness is its ability to perform better than the placebo, more pain-drug trials are failing than in the past. But, interestingly, the researchers found that this increase was only true for studies conducted in the U.S.So what the heck is happening? Why would this effect only show up in the States? Well, Jeffrey Mogil, PhD , the study's lead author, says there are two possibilities: "Either there's something about Americans, or there's something about American trials."Trials conducted in the U.S. have certainly changed a lot. These days, they're both larger (consisting of at least 400 people in the placebo group alone) and longer (lasting for 12 or 16 weeks) than those done abroad, which usually involve around 70 people getting the placebo and which only last for up to six weeks. And we do have strong, clear data suggesting that longer, bigger trials have bigger placebo effects. But the question remains: Why?At this point, there's no clear answer (and Dr. Mogil confesses there's disagreement even among the authors of this study). But one potential reason is that bigger, longer trials probably also come with better funding. This might translate to study materials that are more professional-looking, or interactions with testing staff that are more pleasant. Both of these things may (even subtly) make us think, "Wow, these researchers must really be onto something!" thus setting the placebo effect in motion But Americans have a unique relationship with drugs and the companies that make them. Only in the States and New Zealand can pharmaceutical companies advertise directly to consumers. So, we're bombarded with messages about all kinds of medication that the rest of the world doesn't see. Although it would be hard to ever prove this, says Dr. Mogil, it could be that Americans just have more faith in the generic idea that "drugs make people feel better."Of course, the placebo effect isn't necessarily a bad thing in and of itself — you're still feeling better! But it's becoming an increasingly difficult bar for new drugs to get over, potentially keeping effective medication out of patients' hands. So this is a big problem that's worth solving, even if it takes an extra spoonful of sugar to do it.