The purpose of this study was to identify subgroups of early adolescents based on their history of initiation and recent substance use, examine changes in their subgroup membership across two waves, and evaluate whether sociodemographic characteristics were associated with longitudinal changes in substance use patterns. Methods: Participants were 1,811 early adolescents (72% Black, 53% female) attending middle schools in neighborhoods with high rates of violence and residents with incomes below the federal poverty level. Latent class analysis identified subgroups of adolescents with different substance use patterns at two waves 3 months apart. Latent transition analysis then examined changes in subgroup membership over time and the impact of sex, grade, and time of year on the likelihood of transitioning subgroups. Results: Four patterns were identified: Non-use (76% of sample at wave 1, 73% at wave 2), Initiation (11%, 13%), Alcohol Use (7%, 7%), and Polysubstance Use (6%, 7%). Instability in membership in the Alcohol Use and Polysubstance Use subgroups across waves indicated that early adolescents varied in the number of types of substances they used across 3-month intervals. Female adolescents and eighth grade students were most likely to endorse past 30-day polysubstance use. Conclusions: These findings indicate that membership in substance use subgroups changes even across several months, and that older middle school students are more likely to report polysubstance use. Early adolescence is an important period for early interventions to prevent stability and escalation of use among those who have initiated substance use.
(Publisher abstract provided.)