Comorbid Trajectories of Cigarette Smoking, Alcohol Use, and Marijuana Use from Mean Ages 14–37 Years (N=806).
Note: The substance use scales were coded as follows: Cigarette smoking - none (0), less than daily (1), 1–5 cigarettes a day (2), about half a pack a day (3), about a pack a day (4), and about 1.5 packs a day or more (5). Alcohol use (beer, wine, or hard liquor) - none (0), 3 times a month or less (1), once a week or several times a week (2), 1 or two drinks every day (3), and 3 or more drinks every day (4). Marijuana use - none (0), a few times a year or less (1), once a month (2), several times a month (3), once a week (4), several times a week (5), and daily (6).