Tuesday, February 23, 2010

Placebo Effect in Drug Tests

It's common practice for FDA tests to prove their worth in 'double blind' tests: the dispenser and the recipient both don't know who gets the sugar pills, who gets the real thing. That way, one can account for the well documented placebo effect, which is that people respond positively to any putative action. But, it turns out this isn't really well captured. From the New Yorker:
But antidepressants have side effects, and sugar pills don’t. Commonly, side effects of antidepressants are tolerable things like nausea, restlessness, dry mouth, and so on. This means that a patient who experiences minor side effects can conclude that he is taking the drug, and start to feel better, and a patient who doesn’t experience side effects can conclude that she’s taking the placebo, and feel worse. On Kirsch’s calculation, the placebo effect—you believe that you are taking a pill that will make you feel better; therefore, you feel better—wipes out the statistical difference [in most psychiatric drugs].

Yikes! That seems like a major blunder. Given the FDA bureaucracy, I doubt it's going to be addressed anytime soon (ie, before I die).


Caveat Bettor said...

No test is perfect (a la Heisenberg), but I think that the double-blind method can provide useful information for other medical prescriptions, such as vaccines.

Anonymous said...

I have always wondered about this effect, moreso recently. When I was having (worse) chronic pain issues it was *extremely depressing* to try a medicine that was supposed to work, and have it do nothing for me. This made me wonder if all those results showing increased suicide rates for people taking antidepressant drugs were because people get despondent when the medicines don't work for them. Now because the trials are double blind you argue that they don't know they're on the drug, but perceptive people can often tell based on side effects (and depressed people are often pretty perceptive).