group assignment. Participants who reported complete abstinence (not even a puff of a cigarette) for at least the 7 days prior to the assessment were asked to complete an in-person visit for biochemical verification of abstinence. Saliva cotinine testing was performed for participants who reported abstinence at a given time-point using a gas–liquid chromatography method (66). Cotinine is the major proximate metabolite of nicotine and has a much longer half-life than nicotine, making it the preferred biomarker for tobacco use.
