Cannabis plus opioid co-dependence worsens cognitive impairment beyond opioids alone

What the researchers found

The OD+CD group completed significantly fewer categories on the Wisconsin Card Sorting Test than healthy controls and had more non-perseverative errors. Both OD and OD+CD groups showed verbal working memory deficits. Interestingly, the OD+CU (cannabis use without dependence) group performed better than controls on one trail-making measure.

Why it matters

Cannabis is often viewed as relatively benign compared to opioids, but when combined with opioid dependence, cannabis dependence appears to add measurable cognitive burden. This has implications for treatment planning and cognitive rehabilitation.

The numbers in context

496 participants (97.5% men). OD+CD: fewer WCST categories completed, more non-perseverative errors than HC. OD and OD+CD: more verbal working memory 2-back errors than HC. OD+CU: fewer TMT-B errors than HC.

How the study worked

Cross-sectional controlled study comparing cognitive function across 268 opioid-dependent (OD), 58 OD with cannabis use (OD+CU), 115 OD with cannabis dependence (OD+CD), and 68 healthy controls using SPM, WCST, IGT, TMT, and n-back tests.

What this study cannot tell us

Overwhelmingly male sample (97.5%). Cross-sectional design cannot determine if cognitive deficits preceded or resulted from substance use. Cannabis use versus dependence distinction is clinical, not biological.

How to read the evidence

Reasonable sample sizes with appropriate controls and validated neuropsychological tests, but cross-sectional design and overwhelmingly male sample limit generalizability.

When this study was published

2025 publication.

The bigger picture

The unexpected finding that cannabis use (without dependence) was associated with better performance on one measure challenges simple additive models of substance-related cognitive impairment and suggests moderate cannabis use may not compound opioid-related deficits.

Questions still open

• Why did cannabis use (without dependence) appear protective on trail-making performance?
• Do the additive cognitive deficits of cannabis+opioid dependence reverse with dual abstinence?

Common questions

Read the original research

Neurocognitive Dysfunctions in People with Concurrent Cannabis Use and Opioid Dependence: A Cross-Sectional, Controlled Study.

Journal of psychoactive drugs, 57(1), 71-83

Citation

Ghosh, Abhishek; Shaktan, Alka; Verma, Abhishek; Basu, Debasish; Rana, Devender K; Nehra, Ritu; Ahuja, Chirag K; Modi, Manish; Singh, Paramjit. (2025). Neurocognitive Dysfunctions in People with Concurrent Cannabis Use and Opioid Dependence: A Cross-Sectional, Controlled Study.. Journal of psychoactive drugs, 57(1), 71-83. https://doi.org/10.1080/02791072.2024.2308213

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