Despite marijuana use doubling among Chilean adolescents between 2009 and 2013, the massive school strike and occupation movement of 2011 had no detectable causal effect on substance use.
Read this if you want to understand whether social disruptions like school strikes actually increase youth drug use.
Marijuana use doubled among Chilean teens, but school protests were not the cause
What the researchers found
Marijuana use among Chilean adolescents doubled between 2009 and 2013, coinciding with a massive student movement in which hundreds of schools were occupied by students. However, after controlling for secular trends and school characteristics using a fixed-effects difference-in-difference model, there was no evidence that schools directly affected by strikes and occupations had different substance use outcomes.
The increase in marijuana use appeared to be part of broader social changes occurring among the school-age population rather than a consequence of the protest movement itself. Neither marijuana initiation, marijuana use, alcohol use, nor heavy use showed any causal link to school occupations.
Why it matters
Social movements and disruptions to normal routines are often blamed for increases in youth substance use. This study provides rigorous causal analysis showing that the dramatic 2011 Chilean school occupation movement, despite affecting large numbers of adolescents, was not responsible for the contemporaneous increase in marijuana use.
The numbers in context
Marijuana use doubled from 2009 to 2013 among Chilean adolescents. No significant causal effect of school occupations on: marijuana initiation, marijuana use, alcohol use, or heavy use. Data spanned 2005-2015, grades 9-12.
How the study worked
School-level aggregated panel design using five waves of the National Drug Surveys among Secondary Students (2005-2015) for students in grades 9-12. Fixed-effects difference-in-difference models compared schools that were occupied during 2011 with those that were not, before and after the movement.
What this study cannot tell us
Ecological design using school-level aggregated data may miss individual-level variation. The movement was widespread, making it difficult to find true "control" schools. Other unmeasured factors may have changed simultaneously. The study cannot identify what did cause the marijuana increase if not the movement.
How to read the evidence
Panel study using difference-in-difference analysis, a strong quasi-experimental design for causal inference. Good methodology but limited by school-level aggregation.
When this study was published
Published in 2017. The study provides a useful methodological template for evaluating claims that social disruptions cause substance use changes.
The bigger picture
The finding that a major social disruption did not drive substance use increases challenges common assumptions about the causes of changing drug use patterns. Instead, the increase in Chilean adolescent marijuana use appears to reflect broader cultural shifts in attitudes toward cannabis that affected the entire youth population regardless of their involvement in protests.
Questions still open
- What broader social changes drove the doubling of adolescent marijuana use in Chile? Do other social disruptions (natural disasters, pandemics) have different effects on youth substance use? Would individual-level data reveal subgroup effects masked by school-level aggregation?
Common questions
If the protests didn't cause the increase, what did?
How did they determine the protests weren't the cause?
Read the original research
School collective occupation movements and substance use among adolescents: A school-level panel design.
Drug and alcohol dependence, 176, 21-27
Citation
Castillo-Carniglia, Alvaro; Kaufman, Jay S; Pizarro, Esteban; Marín, José D; Wintemute, Garen; Cerdá, Magdalena. (2017). School collective occupation movements and substance use among adolescents: A school-level panel design.. Drug and alcohol dependence, 176, 21-27. https://doi.org/10.1016/j.drugalcdep.2017.02.025