October 31, 2007


Medical Trials Ignore this Placebo Effect (Ben Harder, October 30, 2007, US News)

[I]f people who are taking the placebo know they are taking the placebo, then there may not be a placebo effect. And if people who are taking the real drug know they're not taking the placebo, they may get an extra psychosomatic boost—a sort of super-placebo effect—from the knowledge that doctors are expecting them to do better than the poor chumps getting the fake medicine. Either way, comparing the two groups at the end of the study could lead researchers to make over-optimistic conclusions about how well a drug works against an underlying physiological condition.

This might happen more often than medical investigators would like to think.

And because they rarely account for the possibility when they design studies, investigators would have no way of knowing which of their conclusions are fatally flawed.

Here's the paragraph (from page 12 of the Oct. 16 issue of Neurology Today, a publication mailed to members of the American Academy of Neurology) that prodded me to think harder about the subject:

"At six months, there was significant improvement in fatigue for the patients treated with antibiotics compared to the placebo. The study authors noted that enough patients receiving antibiotic treatment correctly guessed they were in that group to conclude that this finding might be due to 'unblinding' and a placebo effect."

Hmm. In other words, antibiotics may have produced no true, biological benefit in this trial (which was treating people who had a chronic condition known as post-Lyme syndrome) and only appeared to improve symptoms because patients figured out that they were getting real medicine and unknowingly fooled themselves into thinking they felt better. Sure enough, the medicated patients did no better than placebo-treated patients on two other study measures, including one that measured immunit-related molecules in cerebrospinal fluid.

What's interesting to me is that very few medical investigators do what the authors of this study did: ask their patients whether they think they're getting the real drug or the placebo. And even fewer do any sort of rigorous statistical analysis to rule out the possibility that patients who've figured out which group they're in either improve or don't, according to whether they "should" be improving. At the same time, I'm told, "blinded" investigators (those who during a trial aren't privy to which patients are getting placebo) often discuss their guesses with each other about which patients are getting placebo.

Posted by Orrin Judd at October 31, 2007 2:37 PM
Comments for this post are closed.