When screening for harmful alcohol or cannabis use, we need to avoid focusing only on addiction.
While both substances are potentially addictive (severe use disorder), it is their respective toxicity and impairment properties that carry by far the larger burden of disease (mortality and morbidity) and overall health costs. Thus screening with tools designed mainly to detect probable addiction can miss the mark by a wide margin.
Whereas indicators of addiction are heavily based on reported loss of use-control and related harms, the much larger group at risk can be identified by routinely asking all adult patients how much they use. This can be done once a year along with other aspects of annual medicals.
In the case of alcohol, we can relate their responses in average number of standard drinks per week to evidence-based lower risk drinking guideline upper thresholds: about 10 standard drinks per week for women and 15 drinks for men.
In the case of cannabis we can minimally ask about frequency of use. Daily or near daily use raises the risks for mental health and other harms.
Patients can then be advised and provided with materials guiding them toward making healthier choices about levels of consumption, as well as urging safer modes of use.