Substance Use Assessment Protocol

The use of cigarettes was assessed by one item with response options “I have never smoked” (coded 0), “I used to smoke, but I stopped completely now” (0), “I smoke less than once a week” (1), “I smoke every week, but not every day” (2), and “I smoke every day” (3). The first two response options were both coded 0, as both options indicated no current cigarette use. The use of e-cigarettes and snus was assessed by two additional questions and coded similarly. Alcohol use was measured by one item with response options ranging from 0, “Never”, to 4, “Every week”. Cannabis use and ‘other illicit drug use’ during the previous 12 months were measured with response options ranging from 0, “never”, to 4, “11 or more times”. See Table S1 for a detailed account of all substance use items and their response options.