Instruments

The IYDS survey was adapted from the Communities That Care Youth Survey (23, 24). In 2001, in accordance with recommendations for cross-national instrument development (8), all survey measures underwent cognitive pretesting (9). This pretesting has been previously described in detail; in sum, this process included language review and cross-national item adaptation (9). The survey measures have demonstrated longitudinal validity and reliability when administered to participants in Victoria and Washington State (10, 11). Descriptive statistics for Grade 7 demographic characteristics, Grade7–Grade 8 family environment characteristics, Grade 9 measures of attachment to parents, past year alcohol and cannabis use, and young adult problematic alcohol and cannabis use (Age 25), including Cronbach’s Alpha, are provided in Table 1 .

Descriptive statistics for the study variables.

α, Cronbach’s alpha. n/a, scales with one item and therefore a Cronbach’s alpha could not be calculated. %, percent. χ², chi-square. t, t-statistic. M, mean. SD, standard deviation. Female (coded 0 = male, 1 = female); Victoria (coded 0 = Washington State, 1 = Victoria); Accommodation transitions (coded 0 = no transitions, 1 = transitions); Sibling alcohol use (coded 0 = no use, 1 = recent use); Past year alcohol use (coded 0 = no use, 1 = recent use). Statistically significant state differences for continuous variables calculated using independent t-tests. Statistically significant state differences for dichotomous variables calculated using chi-square tests.

Demographic characteristics were measured in Grade 7. Participants reported their age, gender, and the state in which they lived (Victoria or Washington State). A measure of family socio-economic status was created using parent (mother and father) reported highest level of education (e.g., less than secondary school, completed secondary school, completed post-secondary school) and level of family income (ranging from less than $10,000 to $200,000+ per year). Accommodation transitions were measured using the item “Have you changed homes in the past year?” Response options ranged from “yes” (1) through to “no” (4) and were recoded to reflect “have not changed homes” (reference group) versus “changed homes on one or more occasion” (1) in the past year.

Five scales measured characteristics of the family environment in Grades 7 and 8. Family conflict was measured using three items. “People in my family have serious arguments” is an example item. Nine items, including “My family has clear rules about alcohol and drug use” were used to assess family management. For both scales, response options ranged from “definitely no” (1) to “definitely yes” (4) and were reverse coded such that higher scores indicated lower conflict and better management. Three items examined opportunities for prosocial behavior within the family environment. “If I had a personal problem, I could ask my mom or dad for help” is an example. Response options ranged from “definitely no” (1) to “definitely yes” (4). The scale measuring parental attitudes favorable toward drug use included four items, such as “How wrong do your parents feel it would be for you to use cannabis (pot, weed, grass)?” Response options ranged from “very wrong” (1) to “not wrong at all” (4). The influence of sibling alcohol and cannabis use was assessed using two items: “Have any of your brothers or sisters ever drunk alcohol (like beer, wine or liquor/spirits)?” and “Have any of your brothers or sisters ever used marijuana (pot, weed, grass)?”. Response options were dichotomous, “no” (reference group) and “yes” (1). Participant responses for early adolescent family environment characteristics were averaged to obtain a single scale score across the two waves (Grades 7 and 8).

Attachment to parents comprised four items administered in Grade 9, including “Do you feel very close to your mother?” and “Do you share your thoughts and feelings with your father?”. Response options ranged from “definitely no” (1) to “definitely yes” (4). Alcohol use in the past year at Grade 9 was examined using the item “In the past year (12 months), on how many occasions (if any) have you had alcoholic beverages (like beer, wine or liquor/spirits) to drink—more than just a few sips?”. The item “In the past year (12 months), on how many occasions (if any) have you used cannabis (pot, weed, grass)?” was used to measure cannabis use in the past year. Both items were rated on eight-point scales ranging from “never” (1) through to “40+ times” (8) and recoded to reflect “not at all” (reference group) versus “one or more occasions” (1) in the past year.

Problematic alcohol use was measured at age 25 using the 10-items comprising the Alcohol Use Disorders Identification Test (AUDIT; 25). “How often during the last year have you found that you are unable to stop drinking once you had started?” and “How often during the last year has a relative, a friend, or a doctor or other health worker been concerned about your drinking or suggested that you cut down on your drinking?” are example items. Items were answered on a five-point scale of “never” (1), “monthly or less” (2), “2–4 times a month” (3), “2–3 times a week” (4), or “4 or more times a week” (5). Participants reporting no lifetime and no past year alcohol use were included as “never” for problematic alcohol use. Scores across all scale items were summed to form a total AUDIT score (0–35), where higher scores indicated more problematic alcohol use. Total scores were then recoded as per established guidelines into “low risk,” “risky,” “harmful,” and “high risk” alcohol use. Given the low prevalence of high-risk use in the current sample, harmful, and high-risk categories were combined. This is not uncommon with non-clinical samples. The final recoded AUDIT variable reflected levels of problematic use as being “low risk” (0), “risky use” (1), and “harmful/high risk” (2).

Nine items were used to measure problematic cannabis use. “Over the past year (12 months) how often has your use of marijuana caused you to feel anxious or depressed?” and “Over the past year (12 months) how often has your use of marijuana caused you to feel you couldn’t get through the week without it?” are example items. Each item was rated on an eight-point scale ranging from “never” (1) through to “40+ times” (8). Participants reporting no lifetime or past year cannabis use were included as “never” for problematic cannabis use. Scores across all scale items were summed to form a total problematic cannabis use score (0–27), where higher scores indicated more problematic cannabis use. Total scores were then categorized as per established guidelines (26) into “low risk,” “risky,” “harmful,” and “high risk” cannabis use. Given the low prevalence of participants in high and harmful risk categories, the item was recoded to reflect “no risk” (reference group) versus “risky use” (1).