LAUSR

We studied the association between individual and contextual variables and the use of tobacco, alcohol, or cannabis in the last 30 days preceding the study, considering the hierarchical nature of students nested in schools. We used the 7th Chilean National School Survey of Substance Use (2007) covering 45,273 students (aged 12-21 years old) along with information from 1465 schools provided by the Chilean Ministry of Education. Multilevel univariable and multivariable logistic regression models were performed. We found a significant intra-class correlation within schools for all substances in the study. Common (e.g., availability of pocket money, more time spent with friends, poor parental monitoring, poor school bonding, bullying others, and lower risk perception of substance use) and unique predictors (e.g., school achievement on national tests) were identified. These findings may help in planning and conducting preventive interventions to reduce substance use.