Initiation of Intoxication and Marijuana Use Among American Indian and White Youth Living on or Near Reservations

Past studies comparing initiation of marijuana and alcohol use or intoxication have found large differences between reservation-based Indian youth and youth nationally. However, little research has looked at differences by ethnicity for youth who attend the same schools.

Study participants were AI and white students from schools on or near reservations that have at least 20% AI youth enrolled. Yearly recruitment was based on a sampling scheme to approximate the percentage of AI youth residing in six geographic regions.  Four years of student data (2009-2012) from 32 schools in 3 regions (Northern Plains, Southwest, Upper Great Lakes) were used in the present study.  Students were administered The American Drug and Alcohol Survey^TM, a survey that has been refined for use with AI youth.  Initiation of intoxication and marijuana use were measured by items asking “How old were you the first time you got drunk/tried marijuana?”  We utilized a multi-level discrete-time proportional odds model (Singer & Willett, 1993) that allows for inclusion of time-invariant (gender, ethnicity, region) and time-dependent covariates (age) and that properly models right censored data due to some youth not initiating alcohol use before the end of the study. Because the data are cross-sectional, the first step was to construct a retrospective person-period data set following techniques proposed by Reardon, Brennan, and Buka (2002). 

Comparing cumulative rates of intoxication initiation by ethnicity shows that by age 17, 50.4% of white youth had initiated intoxication compared to 61.7% of AI youth.  The hazard model showed that AI youth had, on average, initiation odds ratios 2.3 times those of comparable white youth at all ages.  There were few other significant differences by ethnicity or gender. Turning to marijuana, approximately 2/3 of AIs reported initiating marijuana use by 17 years old, compared to just over 1/3 of white youth.  The hazard model showed a very large difference in initiation between AI and white youth at all ages, though the difference became less with increased age.  An AI 10 year old (or younger) female had odds of initiating marijuana use 10.5 times higher than those of a similar white female. For males, this odds ratio was 7.2. 

This study shows that there are large differences in initiation rates for AI and white youth even when comparing youth who attend the same schools.  Identifying the particular risk factors leading to these persistent differences, given the similar school and community environments, is imperative to better targeting prevention efforts for these youth.