Factors associated with illegal substance use initiation among young students in Mexico City.

INTRODUCTION AND AIMS To assess risk factors for illegal substances use initiation in a cohort of Mexican high-school teenage students. DESIGN AND METHODS Longitudinal study of a cohort of 10th grade students, with follow up at the time of their enrolment in college (3-4 year follow up). The associations of parental educational level, alcohol abuse in the family, employment status, experiences of physical and sexual aggression, sexual initiation, emotional distress and previous legal substance use at the baseline measurement, with the initiation of illegal substance use were explored. RESULTS The follow-up analysis was carried out in 21,616 at-risk students. The incidence of substance use initiation was 7%. Male gender (odds ratio 3.86, 95% confidence interval 3.45, 4.32), a higher father's education level, sexual initiation for women (odds ratio 2.67, 95% confidence interval 1.49, 4.79] and use of legal substances at baseline were associated with risk of substance use initiation. DISCUSSION AND CONCLUSIONS The social circumstances surrounding adolescents influence their risk of illegal substance consumption. Although the complex network of factors affecting substance use requires further exploring, young people at risk can be identified and should receive preventive attention.