Please use this link to access this publication. Abstract Background Amidst cannabis legalization efforts and laws, we do not fully understand how the youngest frequent cannabis users fare during young adulthood. This study aims to 1) examine the prevalence of cannabis use during adolescence, and 2) investigate links of frequent (i.e., weekly or daily) teenage cannabis use with psychopathology and functional well-being at age 20—compared to no or occasional use. Methods Data came from a prospective-longitudinal cohort study (assessments from 2004 to 2018, from ages 7–20) in an urban setting (N = 1482). Substance use was assessed with self-reports between ages 13 and 20. At age 20, participants reported on psychopathology (psychotic...