variability in their class size. Fourth, while self-report of perceived peer use is commonly studied, and does not significantly differ from actual peer use52, it is possible that it is less objective than reports by peer nominees53. Furthermore, as we did not have reports of concurrent peer cannabis use at older ages (and the sample has a diverse age range at final assessment), we cannot speculate whether trajectory membership was associated with subsequent affiliations with cannabis-using peers. Fourth, we binned frequency of use data into 20-unit intervals and this may have obscured the identification of smaller classes. For instance, our method combined those using 1–2 times in the past year with those who may have used cannabis 15–20 times. However, sensitivity analyses with 10-unit intervals provided similar results. It is also possible that reported frequency at the upper end of use was imprecise (e.g., using 550 vs. 600 times).
