Over 20+ years, cannabis use at admission to methadone treatment increased in Las Vegas (where cannabis was legalized) but not in Tel Aviv, and cannabis use predicted shorter treatment retention in both settings.
Addiction medicine specialists, methadone clinic administrators, and policymakers evaluating cannabis legalization effects on substance abuse treatment.
Cannabis use at methadone admission increased in legalized Las Vegas but not Tel Aviv
What the researchers found
The Las Vegas clinic (1,724 patients) had lower one-year retention than Tel Aviv (1,014 patients): 46.4% vs. 74.4%. Cannabis and benzodiazepine misuse at admission increased in Las Vegas but not Tel Aviv. Cannabis at admission predicted shorter retention in Las Vegas, and cannabis after one year predicted shorter retention in Tel Aviv. Age at admission and retention rates decreased in Las Vegas but increased in Tel Aviv.
Why it matters
Cannabis legalization may increase cannabis use among opioid-dependent individuals in treatment, and this study suggests that cannabis use is associated with worse methadone treatment outcomes regardless of the legal context.
The numbers in context
1,724 Las Vegas patients, 1,014 Tel Aviv patients. One-year retention: 46.4% LV vs. 74.4% TA. Cannabis at admission increased in LV only. Cannabis predicted shorter retention in both clinics (different time points).
How the study worked
Retrospective comparison of patient characteristics and outcomes at two methadone maintenance treatment clinics over 20 years (Las Vegas) and 27 years (Tel Aviv). Admission characteristics, urine drug screens at months 1 and 13, and cumulative retention analyzed by year of admission.
What this study cannot tell us
Retrospective chart review with many potential confounders. Two clinics in very different cultural and healthcare contexts. Cannabis use determined by urine screens and charts, not standardized assessment. The clinics differed in many ways beyond cannabis legality.
How to read the evidence
Long-term two-site comparison with objective urine data, but many confounders and fundamental differences between clinics and countries.
When this study was published
2021 study analyzing 20-27 years of data. One of few studies comparing methadone outcomes across jurisdictions with different cannabis laws.
The bigger picture
As cannabis legalization expands, its impact on addiction treatment outcomes for other substances deserves attention. This cross-national comparison suggests legalization may increase cannabis use in vulnerable populations.
Questions still open
- Would cannabis-specific interventions within methadone programs improve retention? Does the type or frequency of cannabis use matter for treatment outcomes? Could differences in healthcare systems explain some retention differences?
Common questions
Did cannabis legalization hurt methadone treatment outcomes?
Why was retention so different between the clinics?
Read the original research
Trend differences over 20 years between two methadone maintenance clinics, one with and one without cannabis legalization.
Journal of addictive diseases, 39(2), 226-233
Citation
Adelson, Miriam; Smith, Dinita; Peles, Einat. (2021). Trend differences over 20 years between two methadone maintenance clinics, one with and one without cannabis legalization.. Journal of addictive diseases, 39(2), 226-233. https://doi.org/10.1080/10550887.2020.1848248
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