Cannabis use shortened methadone treatment retention, except in patients with schizophrenia | Research

The takeaway

Among 877 methadone patients followed for up to 24 years, cannabis use was associated with shorter treatment retention (6.0 vs 9.1 years), but this effect was not observed in the 50 patients with schizophrenia or chronic psychosis.

Addiction medicine specialists, psychiatrists treating dual diagnosis patients, and methadone program administrators.

Cannabis users stayed 3 years less, except in schizophrenia patients

What the researchers found

Cannabis-using methadone patients had significantly shorter cumulative retention (6.0 years) than non-users (9.1 years). However, among 50 patients with schizophrenia/chronic psychosis, cannabis use was not associated with reduced retention. Survival was shorter for schizophrenia patients who did not use cannabis.

Why it matters

Cannabis use during methadone treatment is common and controversial. This study suggests its effects on treatment retention may differ based on psychiatric comorbidity, with a potentially neutral or even protective role in psychosis patients.

The numbers in context

877 patients total. 50 (5.7%) had schizophrenia/chronic psychosis. Non-psychosis cohort: cannabis users 6.0 years retention vs non-users 9.1 years (p<.001). Psychosis cohort: cannabis users 9.9 years vs non-users 7.9 years (p=.5). Survival shorter for psychosis non-cannabis-users (15.2 years) vs non-psychosis non-users (18.5 years, p=.009).

How the study worked

Retrospective cohort of 877 methadone maintenance patients with DSM-IV psychiatric diagnoses, followed from June 1993 to December 2017. Cannabis use assessed by urine drug screens at admission and after one year.

What this study cannot tell us

Small psychosis subgroup (n=50, only 9 cannabis users). Retrospective design. Cannabis use measured only at two timepoints. Cannot account for chronicity or quantity of cannabis use.

How to read the evidence

Moderate: large cohort with long follow-up, but retrospective design and very small psychosis subgroup.

When this study was published

Published in 2022.

The bigger picture

The idea that cannabis might not harm, and could potentially benefit, opioid treatment retention in patients with psychosis challenges the uniform prohibition of cannabis in addiction treatment settings.

Questions still open

Why might cannabis not harm retention in psychosis patients? Could cannabis be self-medicating psychiatric symptoms in ways that support treatment? Would prospective studies with larger psychosis samples confirm these findings?

Common questions

How much shorter was retention for cannabis users?

Cannabis-using patients stayed in methadone treatment an average of 6.0 years compared to 9.1 years for non-users, a difference of over 3 years.

Why was schizophrenia an exception?

The reasons are unclear. The very small subgroup (only 9 cannabis users with psychosis) limits interpretation. Cannabis may be self-medicating symptoms that would otherwise cause treatment dropout, but this is speculative.

Should methadone programs allow cannabis use?

This study cannot answer that directly. It suggests the relationship between cannabis and treatment outcomes may be more nuanced than blanket policies assume, particularly for patients with psychiatric comorbidities.

Read the original research

Cannabis use is associated with lower retention in methadone maintenance treatment, but not among schizophrenic- and other chronically psychotic patients.

Journal of addictive diseases, 40(2), 183-191

View on PubMed ↗Publisher’s paper ↗

Citation

Volkov, Ilan; Schreiber, Shaul; Adelson, Miriam; Shoshan, Stacy; Peles, Einat. (2022). Cannabis use is associated with lower retention in methadone maintenance treatment, but not among schizophrenic- and other chronically psychotic patients.. Journal of addictive diseases, 40(2), 183-191. https://doi.org/10.1080/10550887.2021.1962209