You've probably heard of the placebo effect, where people's ailments improve when they believe they've been given medicine — even if that medicine is just a sugar pill. Now a new study suggests that the placebo effect can be invoked by advertisements, too.


A group of University of Chicago scientists conducted an experiment to see how well Claritin ads affected the antihistamine's effectiveness. In the abstract for the Proceedings of the National Academy of Science paper where they recorded their results, the authors write:

We conducted randomized clinical trials to examine the impact of direct-to-consumer advertisements on the efficacy of a branded drug. We compared the objectively measured, physiological effect of Claritin (Merck & Co.), a leading antihistamine medication, across subjects randomized to watch a movie spliced with advertisements for Claritin or advertisements for Zyrtec (McNeil), a competitor antihistamine. Among subjects who test negative for common allergies, exposure to Claritin advertisements rather than Zyrtec advertisements increases the efficacy of Claritin. We conclude that branded drugs can interact with exposure to television advertisements.


There's a lot to unpack here. First of all, the ads only triggered the placebo effect in people who did not actually suffer from allergies. So the antihistamine's greater effectiveness was only registered in people who are, in some basic sense, not the target market for these ads. Also, it's not clear whether the Claritin ads boosted the drug's effectiveness, or whether the Zyrtec ads made it less effective. So we don't know if there's some kind of negative placebo effect caused by ads from a competitor (which also, orthogonally, leads to interesting questions about the effectiveness of political attack ads).

But what's really interesting to contemplate is whether this means that we should start prescribing advertising along with drugs. Over at In the Pipeline, chemist and pharma researcher Derek Lowe asks some compelling questions along these lines:

Does direct-to-consumer advertising actually increase the efficacy of the drugs it advertises? That is, does the effect shown in this experiment translate to real-world conditions? For how many compounds is this the case, and in what therapeutic classes is the effect most likely to occur? Is there an actual economic or public health benefit to this effect, should it prove to be robust? If so, how large is compared to the money spent on the advertising itself? And if people internalize the idea that advertisements make a drug work better, will advertisements continue to do that at all?

To his last question, we already have a partial answer at least, from studies in stereotype priming. Stereotype priming is sort of the placebo of the interpersonal psychology world. The classic example of stereotype priming comes from experiments where researchers gave a math test to a room full of people, but first told them that women perform far worse than men do on math tests. The women who took the test then performed badly, on average. But when, under the same conditions, the researchers told a room full of people that women perform especially well on math tests, the women performed far better on average. Further experiments have shown that stereotype priming only works when people don't realize they are being primed.

Read the full scientific study in PNAS