Latent class analysis of substance use: Comparison of two American Indian reservation populations and a national sample

Objective: Our goal was to carefully examine disparities in substance use between two American Indian reservation communities and a national sample. We sought to identify characteristic patterns of use-both across and within samples-that could be used to inform intervention efforts aimed at reducing disparities. Method: Latent class analyses were used to identify subgroups within each sample that were characterized by distinctive patterns of use of alcohol and eight drugs; the use patterns and prevalence of subgroups were then compared across samples. American Indian data were from the American Indian Service Utilization, Psychiatric Epidemiology, Risk and Protective Factors Project (AI-SUPERPFP; N = 2,647), which comprised participants from two distinct cultural groups in the Southwest (SW; n = 1,244; 57% female) and Northern Plains (NP; n = 1,443; 52% female). National data were from the public use file of the 1999 National Household Survey of Drug Abuse (NHSDA; N = 39,152; 52% female). Results: Four classes of lifetime users (abstainers, primarily alcohol users, primarily alcohol and marijuana users, and polysubstance users) and three classes of past-year users (abstainers, primarily alcohol users, and alcohol and drug users) were identified in each sample (SW, NP, NHSDA). Despite consistency in classes of users found across these samples, there were notable sample differences in class prevalence. The modal class for lifetime use, for example, was primarily alcohol users in the SW and NHSDA, and primarily alcohol and marijuana use in the NP. The concordance of lifetime and past-year use classes also varied across the three samples, and examination of past-year abstainers in conjunction with lifetime-use class suggested potentially important differences in the stability of substance-use patterns over time. Conclusions: Our findings highlight the utility of latent class techniques for understanding substance use, comparing substance use across populations and identifying key points of intervention, prevention, and treatment within different communities.