The Role of Norms in Marijuana Use Among American Indian Adolescents.

American Indian adolescents residing on reservations report high levels of marijuana use. Understanding the relationships between normative mechanisms and marijuana use in this group can be especially important in designing effective strategies to prevent use. Participants were 3446 students identifying as American Indian in grades 7-12 across four academic years (2009-2012) from 45 schools. Multilevel logistic analysis was used to examine the relationships between lifetime, last month, and frequent marijuana use and measures of the normative environment. Descriptive and injunctive norms were distinctly and directly associated with all measures of marijuana use, with family injunctive norms showing a strong relationship to use (0.49 < OR < 0.58 for a 9th grade student). Family injunctive norms moderated the relationship between descriptive norms and lifetime and last month use (OR = 0.79 and 0.82, respectively), with higher family disapproval associated with a weaker relationship between descriptive norms and use. Anticipatory socialization was positively related to all measures of marijuana use, with the relationship stronger for lifetime and last month use than for frequent use (OR = 1.88, 1.74, and 1.30, respectively). A contextual variable of descriptive norms was related to lifetime and last month use (OR = 1.66 and 1.51, respectively) but not frequent use. These findings reinforce the importance of parental norms in reducing the likelihood of using marijuana. In addition, prevention strategies that increase the perception that healthy behaviors not involving marijuana use are an enjoyable way to socialize may be more effective in preventing occasional marijuana use.