Substance use and early sexual initiation: a study among Brazilian school-aged adolescents

Adolescence is a critical period of biopsychosocial development often marked by engagement in risk behaviors, including psychoactive substance use and early sexual initiation. Emerging evidence suggests a robust association between these behaviors, particularly early sexual debut (i.e. before age 15). This cross-sectional analytical study draws on data from the 2019 National School Health Survey (PeNSE) to examine the relationship between recent psychoactive substance use and early sexual initiation among Brazilian adolescents aged 15-17 years (n = 72,679). Substance use in the past 30 days was assessed for nine substances: alcohol, conventional cigarettes, hookah, electronic cigarettes, clove cigarettes, hand-rolled cigarettes, marijuana, crack and other illicit drugs. Early sexual initiation was reported by 33.3% of participants. Use of all substances was significantly associated with early sexual debut, with the strongest associations observed for crack (adjusted OR = 1.91; 95% CI = 1.56-2.33), marijuana (OR = 1.58; 95% CI = 1.43-1.75), other illicit drugs (OR = 1.50; 95% CI = 1.37-1.64) and alcohol (OR = 1.47; 95% CI = 1.35-1.59). These findings highlight a strong association between recent substance use and early sexual initiation in Brazilian adolescents, underscoring the need for comprehensive, multisectoral public policies that integrate substance use prevention and sexual health education within school, family and healthcare contexts.