We used validated items and cognitively tested24 newly developed survey items with 15 adult smokers prior to finalizing the survey instrument. The baseline prelabeling survey assessed quit attempts in the last month and most secondary outcomes (eTable 1 in Supplement 2), and the baseline post labeling survey assessed demographic characteristics.
The primary trial outcome was attempting to quit smoking during the study. At week 1, week 2, week 3, and week 4 follow-up visits, we asked participants “During the last week, did you stop smoking for 1 day or longer because you were trying to quit smoking?” At week 4 follow-up, we also asked “Since you started the study, did you stop smoking for 1 day or longer because you were trying to quit smoking?” We considered participants to have made a quit attempt if they answered “yes” to any of the quit attempt questions.
We used the message impact framework (eFigure 1 in Supplement 2), a taxonomy of variables that pictorial warnings may affect,13 (link) to guide the selection of secondary outcomes. Secondary outcomes were measured at week 4 follow-up: cognitive elaboration (thinking about the warning message and thinking about the harms of smoking); fear elicited by the warning and negative affect (eg, disgust, anger); perceived likelihood of harm from smoking; positive and negative smoking reinforcement attitudes; quit intentions; number of conversations in the past week about the warning, health risks of smoking, and quitting smoking; number of times forgoing a cigarette in the past week; and quitting smoking (defined as not smoking cigarettes in the 7 days before the week 4 follow-up visit). Participants who had quit smoking did not answer questions about quit intentions and forgoing a cigarette.