Cannabis use among methadone patients increased only in Las Vegas (where legal) and predicted worse treatment retention in both clinics

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.

Adelson, Miriam et al.·Journal of addictive diseases·2021·Moderate EvidenceRetrospective Cohort
RTHC-02948Retrospective CohortModerate Evidence2021RETHINKTHC RESEARCH DATABASErethinkthc.com/research

Quick Facts

Study Type
Retrospective Cohort
Evidence
Moderate Evidence
Sample
N=1,724

What This Study 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.

Key Numbers

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 They Did This

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.

Why This Research 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 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.

What This Study Doesn't 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.

Questions This Raises

  • ?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?

Trust & Context

Key Stat:
Cannabis use at methadone admission increased in legalized Las Vegas but not Tel Aviv
Evidence Grade:
Long-term two-site comparison with objective urine data, but many confounders and fundamental differences between clinics and countries.
Study Age:
2021 study analyzing 20-27 years of data. One of few studies comparing methadone outcomes across jurisdictions with different cannabis laws.
Original Title:
Trend differences over 20 years between two methadone maintenance clinics, one with and one without cannabis legalization.
Published In:
Journal of addictive diseases, 39(2), 226-233 (2021)
Database ID:
RTHC-02948

Evidence Hierarchy

Meta-Analysis / Systematic Review
Randomized Controlled Trial
Cohort / Case-ControlFollows or compares groups over time
This study
Cross-Sectional / Observational
Case Report / Animal Study

Looks back at existing records to find patterns.

What do these levels mean? →

Frequently Asked Questions

Did cannabis legalization hurt methadone treatment outcomes?

Cannabis use at admission increased only in Las Vegas (where legal), and cannabis use predicted shorter treatment retention. However, many other factors differed between the clinics, so a direct causal link to legalization cannot be established.

Why was retention so different between the clinics?

Las Vegas had 46.4% one-year retention versus 74.4% in Tel Aviv. Multiple factors likely contribute, including different healthcare systems, patient populations, and treatment approaches, not just cannabis policies.

Read More on RethinkTHC

Cite This Study

RTHC-02948·https://rethinkthc.com/research/RTHC-02948

APA

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

MLA

Adelson, Miriam, et al. "Trend differences over 20 years between two methadone maintenance clinics, one with and one without cannabis legalization.." Journal of addictive diseases, 2021. https://doi.org/10.1080/10550887.2020.1848248

RethinkTHC

RethinkTHC Research Database. "Trend differences over 20 years between two methadone mainte..." RTHC-02948. Retrieved from https://rethinkthc.com/research/adelson-2021-trend-differences-over-20

Access the Original Study

Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.

This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.