BACKGROUND: Social media frequently promotes e-cigarette use, and strategies are needed to counter these effects.
METHODS: An online experiment was conducted with 18-24 year old Mexicans (N=699) who were current users of or susceptible to use only cigarettes (23.9% and 7.6%, respectively), only e-cigarettes (2.1% and 3.6 %), or both products (26.9% and 35.9%). Participants were randomized to one of four social media posts from an influencer endorsing a disposable e-cigarette with a brand hashtag: 1) post only Control; 2) post with Nicotine Warning; 3) post with Advertising Disclosure (i.e., #Ad and #PaidPartnership); and 4) Combination: post with nicotine warning and advertising disclaimer. Participants responded to questions about the product: susceptibility (curiosity and accepting friend offers to use it), positive expectancies (would enjoy using it), and risk perceptions (addictiveness, harmfulness), with responses dichotomized to indicate No ("definitely not" or "probably not") or Yes ("probably yes" or "definitely yes"). Separate logistic models regressed each of these outcomes on treatment (reference=control).
RESULTS: Participants exposed to the nicotine warning either alone or combined with the ad disclosure were less likely to be curious to try the product (OR=0.54, 95% CI 0.35–0.83 and OR=0.54, 95% CI 0.34–0.84, respectively), would try it if offered by a friend (OR=0.59, 95% CI 0.39–0.90 and OR=0.55, 95% CI 0.36–0.85, respectively), or would enjoy using it (OR=0.64, 95% CI 0.42–0.97 and OR=0.65, 95% CI 0.43–1.00, respectively). No experimental condition was associated with risk perceptions.
CONCLUSIONS: Including a nicotine warning on a social media post promoting e-cigarettes reduced youths' susceptibility to and positive expectancies about e-cigarette use but not risk perceptions. Ad disclosures did not increase these effects. These findings suggest a potential for using nicotine warnings to reduce e-cigarette use, but further research is needed to assess behavioral effects under ecologically valid conditions.