The outcome variables
The three outcome variables were: self-report of not having smoked in the past four weeks assessed at six months (yes = 1, no = 0, in 1407 participants), change in daily cigarette consumption between baseline and six months (only among those who were still smoking and reported cigarettes/day at six months, 673 participants), and relapse to smoking at six months (yes = 1, no = 0, in 502 participants who had stopped smoking at one month). Change in cigarettes/day is a continuous variable calculated as follows: cigarettes/day after six months minus cigarettes/day at the beginning of the study, a negative value means a decrease in cigarettes/day.