Effects of plain packaging, warning labels, and taxes on young people's predicted sugar-sweetened beverage preferences: An experimental study

Background: Consumption of sugar-sweetened beverages (SSBs) is associated with increased risk of obesity, diabetes, heart disease and dental caries. Our aim was to assess the effects of plain packaging, warning labels, and a 20 % tax on predicted SSB preferences, beliefs and purchase probabilities amongst young people. Methods: A 2 × 3 × 2 between-group experimental study was conducted over a one-week period in August 2014. Intervention scenarios were delivered, and outcome data collected, via an anonymous online survey. Participants were 604 New Zealand young people aged 13-24 years who consumed soft drinks regularly. Participants were randomly allocated using a computer-generated algorithm to view one of 12 experimental conditions, specifically images of branded versus plain packaged SSBs, with either no warning, a text warning, or a graphic warning, and with or without a 20 % tax. Participant perceptions of the allocated SSB product and of those who might consume the product were measured using seven-point Likert scales. Purchase probabilities were measured using 11-point Juster scales. Results: Six hundred and four young people completed the survey (51 % female, mean age 18 (SD 3.4) years). All three intervention scenarios had a significant negative effect on preferences for SSBs (plain packaging: F (6, 587) = 54.4, p <0.001; warning label: F (6, 588) = 19.8, p <0.001; 20 % tax: F (6, 587) = 11.3, p <0.001). Plain packaging and warning labels also had a significant negative impact on reported likelihood of purchasing SSB's (p = <0.001). A 20 % tax reduced participants' purchase probability but the difference was not statistically significant (p = 0.2). Conclusions: Plain packaging and warning labels significantly reduce young people's predicted preferences for, and reported probability of purchasing, SSBs.