Marijuana use among American Indian adolescents: a growth curve analysis from ages 14 through 20 years.

OBJECTIVE

To describe the developmental course of marijuana use among a group of American Indian adolescents, aged 14 through 20 years.

METHOD

A group of 1,766 American Indian adolescents from 3 culture groups provided repeated measures of 30-day marijuana use twice a year across a 3-year period. Linking 5 age cohorts, hierarchical linear modeling was used to model a curvilinear trajectory of marijuana use. Gender and community differences were examined as well.

RESULTS

Support was found for a "maturational" model of marijuana use across time: Use increased in middle adolescence, peaked in later adolescence, and began to decrease in early adulthood. Both gender and community differences in trajectories were significant as well.

CONCLUSIONS

Marijuana use among American Indian adolescents follows a clear developmental trajectory. Growth curve analysis can provide an additional tool for studying the effects of interventions that may not be apparent in a traditional evaluation design.