Uneven effects of twenty years of Chile's cannabis policy implementation in cannabis onset.

BACKGROUND: In Chile, Laws 19366 and 20000, implemented in 1995 and 2005 respectively, regulated and sanctioned cannabis' personal use, cultivation and trafficking.

METHODS: We use thirteen biannual cross-sectional national surveys data from 1994 to 2018 to examine the effect of Laws 19366 and 20000-using the rate of individuals incarcerated per 100000 population due to drug-related crimes as proxy-on the age of onset of cannabis use over time. We estimate the effect of these policies using a mixed proportional hazards framework that models the transition to first cannabis use in 47,832 individuals aged 12-21.

RESULTS: Overall, changes in these laws did not affect the transition to first cannabis use. However, increases in the rate of individuals incarcerated were associated with decreases on the age of onset of cannabis use in females and individuals living in affluent neighborhoods or in specific regions.

CONCLUSION: We find no evidence of cannabis policy changes affecting the age of onset of cannabis use across all individuals aged 12-21. Policy effects associated with decreases in cannabis onset age in females and individuals from affluent neighborhoods or specific regions can be explained by using theoretical frames that recognize specific dynamics of cannabis supply and demand.