A new placebo analgesia review

Placebo for pain: not exactly amazing? A new review of placebo analgesia concludes that it may be “less powerful than often suspected.”

Indeed, it was really quite lame on average. Alas.

But there’s still some hope for placebo! Massage therapists especially will like some of this. Let’s dig in …

Placebo’s potency has long been questioned, but we still don’t really know how much pain can be eased by faith in a treatment. A new scientific review in the European Journal of Pain is the first major attempt to nail that down in quite a while, and they did it by studying three-armed studies.

I’ve recently shared a couple of two-armed studies that compared a real techno-treatment to a sham (ultrasound and pulsed magnetic fields) — a classic way of testing such things, but basic. Neither of those had a third arm: a “no exposure” group, where subjects get diddly squat. You need that to tease out the difference between a power-of-the-mind placebo effect from many confounders. But such studies are rare: extra arms aren’t cheap, but don’t add much value for most researchers, who aren’t studying placebo itself.

Hohenschurz-Schmidt et al found just 17 trials like this, studying people with back, neck, and other joint pain, or fibromyalgia. The treatments were “physical, psychological and self-management” — all the usual suspects, from massage to icing to TENS to mindfulness apps and cognitive behavioural therapy.

The result? “The average short-term placebo effect was small,” right near the bottom of the scale they used. One might even say the average effect was very small. And probably also brief (although they didn’t have a lot of long-term data to work with).

Maybe the mind isn’t so mighty after all? The data didn’t seem to convince the authors!

“It may be that placebo effects are indeed less powerful than often suspected. However, the small average effect in this sample may also be due to methodological challenges present across all included RCTs, and placebo effects clearly varied in magnitude in our sample. … Various factors … may have led to an underestimation of placebo effects here.”

Maybe they are making excuses for the poor result. A weak average means that stronger placebo is probably not that strong and/or common. But there probably are good reasons to suspect that placebo analgesia can be dialed up. Manual therapists, pay attention now, you’ll like this part …

Studies of hands-on therapies generated more placebo than other kinds of treatment. More than things like, say, a disabled shockwave ultrasound device, and other controls that were less “interactive, personalized, and higher-intensity.”

“The on average larger placebo effect from manual control interventions may speak to the therapeutic potential inherent to human touch and/or to higher perceived credibility and expectations of benefits in these interventions.”

But restrain your equines: they based that on a just a few of the trials they reviewed, not enough data to actually support it. It’s just possible and plausible. We don’t know if it’s true, and it certainly doesn’t tell us how high placebo can soar in ideal conditions.

The potential potency of placebo analgesia remains unknown.