Efficacy of a smoking cessation intervention using smartphones

INTERVENTION: Participants are randomly allocated to the intervention or control group. All participants attend a "background assessment" session at the University of Zurich. They are instructed to use a breathalyzer to measure exhaled carbon monoxide, and are instructed to announce a self‐quit date. All participants receive an end of day diary (short questionnaire) which is filled out daily from 7 days before their quit date until 21 days after their quit date, and a breathalyzer to measure carbon monoxide output daily during this period. Participants are also followed up with a daily diary for three days, six months after their quit date. Participants in the intervention group are additionally instructed to use the “SmokeFree Buddy app” during 28 consecutive days (7 days prior to the quit date and 21 days afterwards). More information on the “SmokeFree Buddy app”: https://www.smokefree.ch/en/buddy‐app/ With the SmokeFree Buddy app participants also have to identify a personal buddy (self‐chosen from the personal social network). These buddies get an instruction on how to connect with the target person and to use the “SmokeFree Buddy app“ during the 28 consecutive days to support the smoker in his/her cessation process. Participants in the control group will have the same setting, but do not receive the mobile intervention “SmokeFree Buddy app” and therefore do not have a supporting buddy. CONDITION: Smoking cessation ; Mental and Behavioural Disorders ; Smoking cessation PRIMARY OUTCOME: 1. Smoking abstinence is measured daily during the 28 day quitting period and for a three day period six months after the quit date, using; 1.1. Subjective self reporting (daily diary questionnaires) of abstinence and and number of cigarettes smoked ; 1.2. Objective exhaled carbon monoxide (in parts per million [ppm]) via Smokerlyzer (iCO Smokerlyzer; Bedfont Scientific Ltd) SECONDARY OUTCOME: 1. Intensity and quality of social support is measured daily using self‐reporting diary questionnaires throughout the 28 day quitting period and for three days six months after the quit date.; 2. Self‐efficacy and action control is measured daily using self‐reporting diary questionnaires throughout the 28 day quitting period and for three days six months after the quit date.; 3. Positive and negative effect is measured daily using self‐reporting diary questionnaires throughout the 28 day quitting period and for three days six months after the quit date. INCLUSION CRITERIA: Adult smoker: 1. 18 years or older 2. Daily smoker (at least one cigarette per day) 3. Intention to quit smoking 4. Own a smartphone with access to mobile internet and daily use 5. Fluent in the German language Buddies: 1. 18 years or older 2. Current non‐smoker (at least 6 months abstinence of tobacco and e‐cigarettes) 3. Own a smartphone with access to mobile internet and daily use 4. Fluent in the German language