A parallel-process latent growth curve model was used to model alcohol and marijuana use (vs. nonuse). Participation in team sports and gender were considered to be time-invariant covariates. The sample consisted of 8,179 youth from the National Survey of Parents and Youth. Data were collected over four yearly rounds. Analysis revealed that being part of a competitive sports team was related to a lower probability of marijuana initiation, but to increased rates of alcohol use over time. Males had significantly higher levels of marijuana initiation and decreases in rates of alcohol use over time; females had significantly greater rate of increase in alcohol use over time. Analysis suggests that youth involved in sports are less likely to use marijuana over time. This information may help to uncover other predictors of use over time and to inform policy making as well design as effective prevention.
Keywords: NSPY; alcohol abuse; alcohol dependence; alcohol use; health promotion; physical activity; population-based survey.