The course of cannabis use seems to be less generalizable than the course of smoking and drinking. Previous research found inconsistent trajectories for cannabis use, including high-stable, inverted U-shaped, and decreasing trajectories. In the RIWA study cannabis declined monotonically from a prevalence rate of 26% at age 16 to 13% at age 29, in line with Lee et al. (2010) and Terry-McElrath and O’Malley (2011). Similar to the course of cannabis use and in line with previous evidence, deviance decreased linearly from a 1-year prevalence rate of 40% at age 16 to 11% at age 29.
