Sustained Availability of Dedicated High School Health Courses and Adolescent Substance Use.

Importance: Adolescent substance use remains a leading preventable cause of morbidity and mortality in the US. Evidence is limited on whether sustained availability of dedicated school-based health coursework is associated with lower substance use prevalence at scale. Objective: To estimate whether sustained availability of a dedicated high school health course was associated with lower student-reported past 30-day substance use prevalence. Design, Setting, and Participants: This cohort study included California public high schools that participated in the California Healthy Kids Survey and were linked to annual University of California Office of the President course lists. Participants included high school students in grades 9 and 11 who completed the California Healthy Kids Survey high school between the 2017 to 2018 school year and the 2023 to 2024 school year. Data were analyzed from January to February 2026. Exposure: School year availability of at least 1 standalone health course that was approved by the University of California Office of the President. Availability was defined as sustained when present for at least 2 consecutive school years. Main Outcomes and Measures: Seven binary indicators of any past-30-day substance use: alcohol use, binge drinking, cigarette smoking, drug use, marijuana use, prescription drug misuse, and vaping. Difference-in-differences with 2-way fixed effects and prespecified event-study analyses were used. Results: The analytic sample included 1 942 640 student survey responses from 915 public high schools across 345 districts and 3499 school years; mean (SD) grade was 10.1 (1.0), and 942 180 responses (48.5%) were from female students. Sustained availability of a dedicated health course was associated with lower school year prevalence of vaping (-1.36 [95% CI, -2.15 to -0.57] percentage points), marijuana use (-1.22 [95% CI, -1.95 to -0.49] percentage points), alcohol use (-1.11 [95% CI, -1.91 to -0.30] percentage points), and binge drinking (-0.70 [95% CI, -1.17 to -0.24] percentage points). Estimates for drug use, prescription drug misuse, and cigarette smoking were smaller and had 95% CIs that included 0. Conclusions and Relevance: In this cohort study of California public high schools, sustained availability of a dedicated health course was associated with modestly lower prevalence in several common forms of adolescent substance use. These findings suggest that sustained, dedicated health coursework may be a scalable component of school-based substance use prevention.