Screening for Cannabis Use in Primary Care Catches More Cases — But Getting People Into Treatment Remains Hard

What the researchers found

Implementation increased cannabis screening from 9 to 153 per 10,000 visits (17-fold) and newly identified CUD from 10 to 17 per 10,000 visits. Treatment initiation for CUD increased by 0.5-1 per 10,000 visits (p=0.006). However, treatment engagement did not significantly change (p=0.147). Treatment initiation and engagement for any drug use disorder overall did not change.

Why it matters

This is the first large-scale trial showing that systematic cannabis screening in primary care can work — dramatically increasing detection and starting more people on treatment. But the engagement gap means screening alone isn't enough.

The numbers in context

Pre: 244,542 patients, 942,400 visits. Post: 287,696 patients, 1,087,565 visits. Screening: 9→153/10,000 visits. New CUD: 10→17/10,000. Treatment initiation: +0.5-1/10,000 (p=0.006). Engagement: no change (p=0.147). 19 sites randomized.

How the study worked

Stepped-wedge cluster-randomized trial across 19 sites in a large primary care system (January 2016 - July 2018). Implementation strategies: practice facilitation, EHR decision support, performance feedback. Pre-post analysis of screening, diagnosis, and treatment rates using EHR and claims data.

What this study cannot tell us

Pre-post comparison within a stepped-wedge design may be confounded by temporal trends. Cannabis legalization changes during the study period may have affected results. Implementation fidelity varied across sites. Treatment engagement definition may be too strict.

How to read the evidence

Stepped-wedge cluster-randomized design across 19 sites with over 2 million visits provides strong evidence for screening effectiveness, with clear demonstration of the engagement gap.

When this study was published

Published 2026, analyzing 2015-2019 implementation data from a large US healthcare system.

The bigger picture

The screening-to-treatment gap — more people identified but no more engaged in treatment — is the central challenge for integrating cannabis care into primary care. It mirrors challenges seen with depression screening and suggests structural barriers beyond detection.

Questions still open

• What barriers prevent identified CUD patients from engaging in treatment? Would integrated treatment (same visit, same provider) improve engagement? Should screening be paired with brief intervention rather than referral?

Common questions

Read the original research

Implementing Care for Cannabis and Other Drug Use in Adult Primary Care: Outcomes of a Cluster-Randomized Implementation Trial.

American journal of preventive medicine, 70(1), 108112

Citation

Matson, Theresa E; Johnson, Eric; Bobb, Jennifer F; Graham, Vina F; Kiel, Linda M; Lee, Amy K; Lapham, Gwen T; Caldeiro, Ryan M; Bradley, Katharine A; Angerhofer, Julie E. (2026). Implementing Care for Cannabis and Other Drug Use in Adult Primary Care: Outcomes of a Cluster-Randomized Implementation Trial.. American journal of preventive medicine, 70(1), 108112. https://doi.org/10.1016/j.amepre.2025.108112

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