https://www.selleckchem.com/products/sodium-2-1h-indol-3-ylacetate.html Little is known about changes in alcohol and cannabis co-use over time in adolescents and young adults. We sought to describe the natural course of alcohol and cannabis co-use from age 12 to 17 and 20 to 31 and to describe frequent (i.e., ≥ once/month) binge drinking (i.e., ≥ 5 drinks/occasion) and cannabis use from age 20 to 31. Data were drawn from two longitudinal studies conducted in Montréal, Canada AdoQuest ( = 1,852) and the Nicotine Dependence in Teens (NDIT) study ( = 1,293). Complete data on alcohol and cannabis were available for 620 12-17-year-olds (58% female) followed from 2005 to 2011 in AdoQuest, and 673 20-31-year-olds (56% female) followed from 2007 to 2020 in NDIT. We reported proportions of co-use, exclusive drinking ("drinking"), exclusive cannabis use ("cannabis use"), frequent co-use, frequent binge drinking, and frequent cannabis use by age and sex. Co-use rose from 2% at age 12-13 to 23% at age 17, was stable at 44% at age 20 and 24, and then decreased to 37% at age 31. Drinking rose from 20% to 51%, and cannabis use was consistently rare (< 2%). During young adulthood, frequent co-use declined from 21% at age 20 to 12% at age 31, and frequent binge drinking declined from 29% at age 20 to 22% at age 31. Frequent cannabis use increased from 6% at age 20 to 11% at age 31. Alcohol and cannabis use should be studied as time-varying behaviors. Co-use patterns should be monitored over time in this population. (PsycInfo Database Record (c) 2021 APA, all rights reserved). Alcohol and cannabis use should be studied as time-varying behaviors. Co-use patterns should be monitored over time in this population. (PsycInfo Database Record (c) 2021 APA, all rights reserved). Recent work has attempted to uncover heterogeneity in experiences of victimization. However, few studies have included important trauma-related characteristics such as known perpetrator, fear of life or injury, and n