It is well known that beliefs about the quality of a drug can enhance its physiological effect, but little is known of the impact of advertising of a branded drug. Kamenica et al (PNAS August 2013) conducted a clinical trial to measure the physiological impact of direct-to-consumer advertising of the antihistamine Claritin. The authors exposed subjects with or without allergies to a skin test of common allergens, and then subjects received Claritin, and viewed advertisements for Claritin or Zyrtec. Regardless of allergy, all subjects experienced a wheal reaction to the skin test. In the allergy subpopulation, there was no significant change in beliefs associated with exposure to Claritin advertisements; however, in the subpopulation without allergies, exposure to Claritin advertisements increased the efficacy of Claritin (16% at 120 minutes). This result suggests that advertising can have strong psychologically mediated physiological effects to a drug.
It is unclear if the results were due to the positive effect of Claritin ads or a negative effect of Zyrtec ads. A small pilot test included a group that did not receive advertisements, but the authors did not replicate this arm in the larger study. A follow –up trial should be conducted to determine if positive or negative advertisements have a greater effect as well as a no advertisement control group.