Countering Demand for Ineffective Health Remedies: Do Consumers Respond to Risks, Lack of Benefits, or Both?

Objective: We tested whether targeting the illusion of causality and/or misperceptions about health risks had the potential to reduce consumer demand for an ineffective health remedy (multivitamin supplements). Design: We adopted a 2 (contingency information: no/yes) × 2 (fear appeal: no/yes) factorial design, with willingness-to-pay (WTP) as the dependent variable. The contingency information specified, in table format, the number of people reporting a benefit vs. no benefit from both multivitamins and placebo, plus a causal explanation for lack of efficacy over placebo. The fear appeal involved a summary of clinical-trial results that indicated multivitamins can cause health harms. The control condition received only irrelevant information. Main outcome measure: Experimental auctions measured people’s WTP for multivitamins. Experiment 1 (N = 260) elicited hypothetical WTP online. Experiment 2 (N = 207) elicited incentivised WTP in the laboratory. Results: Compared to a control group, we found independent effects of the contingency intervention (-22%) and the fear appeal (-32%) on WTP. The combined condition had the greatest impact (-50%) on WTP. Conclusion: We found compelling evidence that consumer choices are influenced by both perceptions of efficacy and risk. The combination of both elements can provide additive effects that appear superior to either approach alone.