Project MARS: design of a multi-behavior intervention trial for justice-involved youth

Marijuana and alcohol use are associated with increased sexual risk behavior among justice-involved youth. A multi-behavior intervention may reduce all three risk behaviors. The purpose of this study is to examine the relationships among multiple risk behaviors and the Theory of Planned Behavior (TPB) constructs guiding the development of the Motivating Adolescents to Reduce Sexual risk (MARS) intervention. We describe the MARS study design to inform the process through which a multi-behavior intervention trial can be implemented and evaluated. Participants completed questionnaires prior to randomization to one of three interventions. Relationships were found between TPB constructs and risk behavior. A single latent variable was inadequate to capture all three risk behaviors. Interventions to reduce sexual risk behavior can include content related to the role of substance use in influencing sexual risk behavior with only minimal modifications to the curriculum, and preliminary data suggest a common theory can apply across risk behaviors.