Sociodemographic measures included gender, race/ethnicity, age, education, employment status, and marital status. Substance use measures (with response options in italics) included: number of cannabis joints or joint equivalents per day on days in which cannabis was used in the past 12 months; frequency of cigarette use in the past 12 months (every day, 5–6 days/week, 3–4 days/week, 1–2 days/week, 2–3 days/month, once a month or less); number of cigarettes per day in the past 12 months; age started smoking cigarettes; and use of at least 50 cigars, use of a pipe at least 50 times, use of snuff at least 20 times, and use of chewing tobacco at least 20 times (yes, no) since the Wave 1 interview. Mixing of tobacco with cannabis was not assessed. Utilization of treatment for drugs or alcohol was defined as seeking professional or non-traditional treatment in the past 12 months. Professional treatment included outpatient visits to a physician, psychologist, or any other professional; inpatient treatment in a drug detoxification or rehabilitation unit, or hospital ward; and treatment in an emergency department. Non-traditional treatment was
