Recruitment and Sample
RECRUITMENT
We recruited participants during early spring of two consecutive years, in the final semester of students’ senior year in high school. Each cohort participated for two full years, from the spring of recruitment through the spring of their second year (fourth semester) in college. We controlled for potential cohort effects by using cohort as a covariate in outcome analyses. The population from which we drew our sample comprised all students admitted to two consecutive first-year university classes, at a single university in the Pacific Northwest region of the United States (CONSORT diagram in We recruited parent-student dyads, contacting students and their parents or caregivers first by letter and email, with follow-up telephone calls explaining the study. To be enrolled in the study, both the student and one parent or caregiver had to agree to participate and then had to complete a baseline survey. Our final sample size was slightly more than our target (The student sample was representative of the university’s first-year student population: 49.6% female and 32.5% first-generation students. (At the time we recruited for the study, the administrative database allowed for only binary gender identification.) Fifty-nine percent (59%) of students reported their race/ethnicity as White, 17.4% as Hispanic/Latinx, 4.5% as Black/African American, 1% as American Indian/Alaska Native, 5.1% as Asian, 0.7% as Hawaiian/Pacific Islander, and 11.3% as two or more races. Average age at recruitment was 18.2 (SD = 0.36, range = 16.7—19.6).Eighty-six percent (There were no statistical differences between groups at baseline on the substance use outcomes. Retention from baseline to first semester was 96% for parents and 94% for students. There was no differential attrition across conditions between the baseline and follow-up surveys.