Warnings of adverse side effects can backfire over time.

Warnings that a promoted product can have adverse side effects (e.g., smoking cigarettes can cause cancer) should dampen the product's allure. We predicted that with temporal distance (e.g., when an ad relates to future consumption or was viewed some time earlier), this common type of warning can have a worrisome alternative consequence: It can ironically boost the product's appeal. Building on construal-level theory, we argue that this is because temporal distance evokes high-level construal, which deemphasizes side effects and emphasizes message trustworthiness. In four studies, we demonstrated this phenomenon. For example, participants could buy cigarettes or artificial sweeteners after viewing an ad promoting the product. Immediately afterward, the quantity that participants bought predictably decreased if the ad they saw included a warning about adverse side effects. With temporal distance (product to be delivered 3 months later, or 2 weeks after the ad was viewed), however, participants who had seen an ad noting the benefits of the product but warning of risky side effects bought more than those who had seen an ad noting only benefits.