This PNAS paper‘s title certainly caught my attention: “Advertisements impact the physiological efficacy of a branded drug”. The authors, from the University of Chicago, are digging into the business end of the placebo effect. After giving a set of subjects a skin-test panel to common allergans, here’s what happened:
We conducted two randomized clinical trials to measure the impact of direct-to-consumer advertising on the objective, physiological effect of Claritin (Merck & Co.), a leading antihistamine drug. A pilot study assessed the efficacy of Claritin across subjects exposed to advertisements for Claritin, advertisements for Zyrtec (McNeil), or control advertisements. . .Among subjects with allergies, the efficacy was the same across the three advertisement conditions, but among subjects without allergies, efficacy was significantly greater in the Claritin advertisements condition than in the Zyrtec advertisements condition.
The heterogeneity of the treatment effect based on the allergy status was discovered only ex post facto, so we conducted a follow- up trial to replicate these initial findings. To maximize statistical power, the follow-up trial used a larger sample, assigned subjects only to Claritin advertisements or Zyrtec advertisements, and block-randomized subjects based on their allergy status. In ad- dition, we elicited subjects’ beliefs about the efficacy of Claritin to examine whether any difference in impact of the advertisements across the two subpopulations is driven by the relative malleability of their beliefs. . .
This reminds me of the various experiences that people have had with blind taste testing of wines. In the follow-up trial, they used a histamine challenge in the skin test, which will give a red reaction no matter what you’re allergic to. The effect repeated:
In the subpopulation without allergies, we find that the efficacy of Claritin at 120 min is substantially higher for subjects who were exposed to Claritin advertisements. Claritin advertisements have no significant impact on efficacy 60 min after the drug is taken. This pattern is consistent with the observed changes in the subjects’ beliefs. Exposure to Claritin advertisements in this subpopulation greatly increases the belief in the efficacy of Claritin. At the same time, the realized efficacy of Claritin at 120 min (but not at 60 min) is strongly correlated with the change in beliefs.
In the subpopulation with allergies, we find no relationship between exposure to Claritin advertisements and the change in beliefs. Moreover, the advertisements have no impact on the efficacy of Claritin at 120 min. We do find a curious negative impact of Claritin advertisements on Claritin’s efficacy at 60 min in this subpopulation, but this effect cannot be mediated by the (nonexistent) impact of advertisements on beliefs.
Oh, boy. I truly wonder why this experiment hasn’t been run before, but look for a lot of follow-ups now that it’s out. As the authors themselves detail, there are several unanswered questions that could be addressed: does seeing the Claritin advertisements make the Claritin work better, or does seeing the Zyrtec ads make Claritin work more poorly? Why does this seem to work only in people without specific allergies in the first place? What’s the physiological pathway at work here, in any case?
Here’s the big one: 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?