The application of group-based trajectory analysis with a zero-inflation specification to understand adaptations in alcohol and marijuana use among sexual minorities during the emerging adulthood period is underutilized. We propose a series of four steps in the application of group-based trajectory analysis for outcomes that follow a zero-inflated distribution. In addition, using a longitudinal cohort study of emerging adult sexual minority men (n = 597) we provide an example of how to obtain group-based trajectory profiles of alcohol and marijuana use among emerging adult sexual minority men with a zero-inflated specification. In addition, we examined racial/ethnic differences in trajectory profiles. Findings suggest that there were five distinct alcohol and marijuana use trajectories that were reliably predicted by racial/ethnic identity for alcohol but not marijuana utilizing the zero-inflated specification. A summary of findings and concluding remarks related to the utility of this modeling technique are presented.
Predicting trajectories of substance use during emerging adulthood: Exploring the benefits of group-based trajectory modeling for zero-inflated outcomes
Testing, Psychometrics, Methodology in Applied Psychology, 27 (3), 291-311. doi: 10.4473/TPM27.3.1.