Cannabis use is common and increasingly legal. What do we know, and how can we advise our patients, about when cannabis use becomes problematic enough to be considered cannabis use disorder (CUD)? Do frequency or potency impact that risk?

To gain more insight regarding frequency, researchers reviewed 6 prospective cohort studies encompassing 40,984 participants between ages 15 and 30, with follow-ups spanning from 3 to 17 years. They identified distinct user groups—nonusers, annual users, monthly users, weekly users, and daily users—and then quantified the rates of CUD across these groups. Unsurprisingly, they found that increased use corresponded with heightened CUD risk.

Results

Specifically, compared to nonusers, relative risk (RR) increased by 2.03 for annual users, 4.12 for monthly users, 8.37 for weekly users, and 16.99 for daily users. Transitioning up one usage category more than doubled CUD risk. To offer a clearer perspective, researchers calculated the absolute risk increase (ARI) as well, which is the overall probability of acquiring CUD. If we assume nonusers had a 0% CUD risk, the ARI was 3.5% for yearly users, 8.0% for monthly users, 16.8% for weekly users, and a staggering 36% for daily users.

This risk profile is further complicated by cannabis potency. A different systematic review published the same year found that high-potency products with >10% tetrahydrocannabinol (THC) significantly increased CUD risk compared to lower-potency products, regardless of frequency of use (Petrilli K et al, Lancet Psychiatry 2022;9(9):736–750). Product potency has been steadily increasing over time, with many dispensaries now selling products with THC levels well above 20%.