Background As evidenced by research on tobacco industry documents, messages that seed uncertainty about product harms helped create more positive public attitudes attitudes towards industry, reduce support for regulation, and deflect potential litigation. There is mounting evidence that other harmful product industries engage in similar tactics, but the extent to which these are effective in generating uncertainty in the mind of the public is unknown. This study aimed to assess the effects of industry and industry-sponsored messages on public understanding across a range of harmful products.

Methods We identified examples of industry-funded alternative causation arguments from the published literature focusing on (i) smoking and lung cancer; (ii) alcohol and breast cancer; (iii) alcohol and pregnancy harms; (iv) sugar-sweetened beverages and obesity; and (V) fossil fuels and climate change. Anonymized Qualtrix panel respondents were randomly assigned to be exposed to either a message on the risk in question from one of four industry-funded organizations (exposure), or one of four independent organizations (un-exposed). Participants were asked about the level of their prior knowledge on the topic before responding, along with age, gender and education level. We ran logistic regression models within each set of argument topics to examine the binary outcome of ‘uncertain/certain it doesn’t increase risk’ vs ‘certain it does increase risk’ in industry vs non-industry texts. We then pooled the results together in a random-effects meta-analysis.

Results In total, across all paired comparisons, n=3284 respondents received industry text and n=3297 received non-industry text. Exposure to industry messages led to significantly greater uncertainty compared to non-industry messages [Odds ratio (OR) 1.60, confidence interval (CI) 1.28–1.99)]. Effect size was greater among those who self-rated as not/slightly knowledgeable (OR 2.24, CI 1.61 – 3.12), or moderately knowledgeable (OR 1.85, CI 1.38–2.48) compared to those very/extremely knowledgeable OR 1.28 (1.03–1.60). Analysis by industry revealed similar trends.

Conclusion This novel randomized controlled study demonstrates that exposure to messages from industry-sponsored organisations significantly increase uncertainty regarding the risk of climate change, sugar sweetened beverages, tobacco and alcohol. The difference in groups was predominantly due to more respondents reporting uncertainty. This evidence brings into question whether industries who produce harmful products and those in receipt of their funding should be permitted to communicate with the public about the harmful impacts and health risks, considering the effect, and the scale of these interventions. More broadly, policy-makers seeking to improve public understanding of risk and policy, should be aware of the spread and potency of commercially driven misinformation.