The impact of strengthening cigarette pack warnings: Systematic review of longitudinal observational studies

Objectives Cigarette pack warnings are a tobacco control strategy used globally. To understand their impact, we systematically reviewed longitudinal observational studies examining national implementation of strengthened warnings. Methods We used comprehensive search procedures to identify observational studies examining the impact of strengthening cigarette pack warnings. We report longitudinal changes in knowledge, beliefs, attitudes, intentions, and behavior. Results We identified 32 studies conducted in 20 countries with 812,363 participants. Studies commonly examined changes from text to pictorial warnings (64%); the remainder examined strengthened text or strengthened pictorial warnings. Knowledge increased in all 12 studies that assessed it. Studies of beliefs/attitudes and intentions showed mixed results. Quitline calls increased in four of six studies, while foregoing of cigarettes did not increase. Cigarette consumption decreased in three of eight studies; quit attempts increased in four of seven studies; and short-term cessation increased in two of three studies. Smoking prevalence decreased in six of nine studies. Conclusions Strengthening warnings was associated with longitudinal increases in knowledge, quitline calls and reductions in smoking behavior. Strengthening warning policies should be a priority for tobacco control globally.