Respiratory sinus arrhythmia as a predictor of substance use among early adolescents Risk behaviors that cause negative health outcomes, such as substance use or sexual risk behaviors, typically begin in adolescence. Identifying those most at risk in early adolescence is critical for prevention interventions. Emotion regulation plays an important role in reducing adolescent risk but detecting those who are vulnerable because of deficits in emotion regulation during early adolescence is challenging due to poor adolescent insight into these still-developing emotional processes. Respiratory sinus arrhythmia (RSA), an index of heart rate variability that is influenced by the parasympathetic nervous system, is an established marker of emotion regulation processes. RSA does not rely on self-report and may be useful for early identification of risk. Our team has developed a novel virtual reality party task with which to assess emotion regulation patterns in adolescents. Pilot data in our laboratory using this task suggest that adolescents with a history of substance use exhibit slower return to baseline RSA (measured at rest) after exposure to a challenging situation (referred to as recovery RSA) compared to non-using peers. This may suggest that recovery RSA is a relevant index of emotion regulation related to risk behaviors, as emotional triggers often occur in rapid succession in real-world risk situations. The proposed study will prospectively examine RSA's utility in predicting adolescent risk behaviors (substance use and sexual risk) among a sample of 280 early adolescents (ages 12.0-12.5 years) for a period of 24 months. We will also evaluate whether emotion regulation in the context of a substance use and sexual risk-taking situation (the virtual reality party) is more useful in predicting risk behavior than a computer risk-taking task (the Balloon Analogue Risk Task). We also will examine strategies for defining recovery RSA, given inconsistencies in the current literature. The current proposal advances the field by combining virtual reality and RSA collection to assess emotion regulation with the aim of identifying markers of those most vulnerable to engaging in risk behaviors at an early age, thus innovating the science of prevention.