Objective To inform international research and policy, we conducted a meta-analysis of the experimental literature on pictorial cigarette pack warnings. Data sources We systematically searched 7 computerised databases in April 2013 using several search terms. We also searched reference lists of relevant articles. Study selection We included studies that used an experimental protocol to test cigarette pack warnings and reported data on both pictorial and text-only conditions. 37 studies with data on 48 independent samples (N=33 613) met criteria. Data extraction and synthesis Two independent coders coded all study characteristics. Effect sizes were computed from data extracted from study reports and were combined using random effects meta-analytic procedures. Results Pictorial warnings were more effective than text-only warnings for 12 of 17 effectiveness outcomes (all p<0.05). Relative to text-only warnings, pictorial warnings (1) attracted and held attention better; (2) garnered stronger cognitive and emotional reactions; (3) elicited more negative pack attitudes and negative smoking attitudes and (4) more effectively increased intentions to not start smoking and to quit smoking. Participants also perceived pictorial warnings as being more effective than text-only warnings across all 8 perceived effectiveness outcomes. Conclusions The evidence from this international body of literature supports pictorial cigarette pack warnings as more effective than text-only warnings. Gaps in the literature include a lack of assessment of smoking behaviour and a dearth of theory-based research on how warnings exert their effects.

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Background Our randomized trial found that pictorial cigarette pack warnings elicited more quit attempts than text-only warnings. Purpose In the current study, we sought to identify psychological mechanisms that explain why pictorial cigarette pack warnings change behavior. Methods In 2014 and 2015, we recruited 2,149 adult smokers in North Carolina and California, US. We randomly assigned smokers to receive on their cigarette packs for 4 weeks either a text-only warning (one of the US’s current warnings on the side of cigarette packs) or a pictorial warning (one of the US’s proposed text warnings with pictures on the top half of the front and back of cigarette packs). Results Pictorial warnings increased attention to, reactions to, and social interactions about cigarette pack warnings (all p<.05). However, pictorial warnings changed almost no belief or attitude measures. Mediators of the impact of pictorial warnings included increased attention, negative affect, social interactions, thinking about the warning and harms of smoking, and intentions to quit (all p<.05). Analyses also found that pictorial warnings led to greater avoidance of the warnings, which was associated with more quit attempts (p<.05). Conclusions Pictorial warnings increased quit attempts by eliciting aversive reactions and by keeping the message vividly in smokers’ minds. Contrary to predictions from several theories of health behavior, the warnings exerted little of their influence through changes in beliefs and attitudes and none of their influence through changes in risk perception. We propose the Tobacco Warnings Model based on these findings.

Policies that require front-of-package (FoP) nutrient warnings are becoming increasingly common across the globe as a strategy to discourage excess consumption of sugary drinks and ultra-processed food. However, a better understanding of the pathway through which FoP nutrient warnings work, as well as a review of how outcomes being measured in recent studies map onto this pathway, are needed in order to inform policy on the most effective FoP label design for reducing purchases of ultra-processed foods. This scoping review describes a conceptual model for how FoP nutrient warnings affect consumer behavior, examines which of these outcomes are currently being measured, and summarizes evidence from randomized controlled experiments. Twenty-two studies which experimentally tested nutrient warnings against a control label or other labeling systems were included for full-text review. Our conceptual model includes attention; comprehension, cognitive elaboration, and message acceptance; negative affect and risk perception; behavioral intentions, and behavioral response, along with other elements such as external factors and interpersonal communications. We found that many studies focused on outcomes such as attention, comprehension, and behavioral intentions, but considerable gaps in the evidence remain, particularly for intermediary steps on the pathway to behavioral change, such as negative affect and social interactions. FoP nutrient warnings were visually attended to by consumers, easy to understand, helped consumers identify products high in nutrients of concern, and discouraged them from purchasing these products, although other labeling systems were perceived as containing more information and performed better at helping consumers rank the healthfulness of products. More research is needed to understand whether and how nutrient warnings work in the real world to discourage consumer purchases of sugary drinks and ultra-processed food.

Background Policymakers worldwide are considering requiring warnings for sugary drinks. A growing number of experimental studies have examined sugary drink warnings' impacts, but no research to our knowledge has synthesized this literature. To inform ongoing policy debates, this study aimed to identify the effects of sugary drink warnings compared with control conditions. Methods and findings We systematically searched 7 databases on June 21, 2019, and October 25, 2019. We also searched reference lists of relevant articles. Two investigators independently screened titles, abstracts, and full texts to identify peer-reviewed articles that used an experimental protocol to examine the effects of sugary drink warnings compared to a control condition. Two investigators independently extracted study characteristics and effect sizes from all relevant fulltext articles. We meta-analyzed any outcome assessed in at least 2 studies, combining effect sizes using random effects meta-analytic procedures. Twenty-three experiments with data on 16,241 individuals (mean proportion female, 58%) were included in the meta-analysis. Most studies took place in Latin America (35%) or the US or Canada (46%); 32% included children. Relative to control conditions, sugary drink warnings caused stronger negative emotional reactions (d = 0.69; 95% CI: 0.25, 1.13; p = 0.002) and elicited more thinking about the health effects of sugary drinks (d = 0.65; 95% CI: 0.29, 1.01; p < 0.001). Sugary drink warnings also led to lower healthfulness perceptions (d = −0.22; 95% CI: −0.27, −0.17; p < 0.001) and stronger disease likelihood perceptions (d = 0.15; 95% CI: 0.06, 0.24; p = 0.001). Moreover, sugary drink warnings reduced both hypothetical (d = −0.32; 95% CI: −0.44, −0.21; p < 0.001) and actual consumption and purchasing behavior (d = −0.17; 95% CI: −0.30, −0.04; p = 0.012). Statistically significant effects were not observed for perceptions of added sugar or positive sugary drink attitudes (p's > 0.10). Moderation analyses revealed that health