Theoretical framework for the study of a personalized smoking cessation intervention, China
NA: not applicable.We designed a message bank for WeChat with a three-layer framework. The first layer was divided based on the timing of messages and consisted of the pre-quitting message (days 1–7), quitting day message (day 8), withdrawal symptom management message (days 9–18), early quit phase message (days 19–36) and late quit phase message (days 37–90). The second layer was divided based on the transtheoretical model. Before the quit day, messages were classified as: strong quitting intention or weak quitting intention. After the quit day, messages were classified as: maintained abstinence or relapsed. The third layer was divided based on the protection motivation theory. Because of some overlap among the seven components of the protection motivation theory, we merged them into three groups: increased severity and susceptibility; decreased response cost and intrinsic and extrinsic rewards; or increased self-efficacy and response efficacy. The core motivational messages consisted of 14 sub-groups with a total of 200 text messages. There were also approximately 200 contact messages. The intervention group participants received partial information, and the information they received varied depending on their smoking status and scores on the protection motivation theory components.The WeChat application calculated each participant’s score in the protection motivation theory by delivering questions and recording information. The programme then automatically calculated the lower score of the components of the model that needed to be strengthened. Specifically, the scale comprised 21 items using a 7-point Likert-type scale with responses ranging from 1 (definitely disagree) to 7 (definitely agree). Each construct of protection motivation theory included three items, and we computed the mean of the sub-scale score. We have published the details of this scale and evaluation process elsewhere.