Background: Over the previous two decades, the prevalence of cannabis use has risen among the population in Mexico. Aims: To estimate the sex- and age-specific rates of onset of cannabis use over time. Design: Time-to-event flexible parametric models with spline specifications of the hazard function. Stratified analysis by sex, and control for temporal trends by year of data collection or decennial birth-cohort. Setting: Mexico. Participants: Pooled sample of 141,342 respondents aged between 12 and 65 years from five nationally representative cross-sectional surveys, the Mexican National Surveys of Addictions (1998, 2002, 2008, 2012) and the Mexican National Survey on Drugs, Alcohol, and Tobacco Consumption (2016). Measurements: We estimated age-specific rates of onset of cannabis as the conditional rate of consuming cannabis for the first time at a specific age. Findings: Age-specific rates of onset of cannabis use per 1,000 individuals increased over time for both females and males. Peak rates per 1,000 ranged from 0.935 (95%CI= [0.754,1.140]) in 1998, to 5.390 (95%CI= [4.910,5.960]) in 2016 for females; and from 7.510 (95%CI= [5.516, 10.355]) in 1998, to 26.100 (95%CI= [23.162,30.169]) in 2016 for males. Across decennial birth-cohorts, peak rates of onset of cannabis use per 1,000 individuals for females ranged from 0.342 (95%CI= [0.127,0.898]) for those born in the 1930s, to 14.600 (95%CI= [13.200,16.100]) for those born in the 1990s; and for males, from 4.900 (95%CI= [0.768, 7.947]) for those born in the 1930s, to 38.700 (95%CI= [32.553,66.341]) for those born in the 1990s.
Conclusion: Rates of onset of cannabis use for males are higher than for females; however, the change across recent cohorts of the rates of onset has increased at a faster rate among females. Our findings can inform and improve the implementation of policies around cannabis use by identifying subpopulations by age, sex, and birth-cohort that are at the highest risk of initiating cannabis consumption