People who use both cannabis and tobacco together may actually perform better cognitively than those who use either substance alone | Research

The takeaway

A systematic review of 39 studies found converging evidence that cannabis and nicotine/tobacco co-use may offset each other's cognitive and brain functional impairments, with co-users showing similar performance to non-users on working memory and brain connectivity.

Addiction researchers, cessation program designers, dual-substance users

Co-users showed similar working memory and brain function to non-substance users

What the researchers found

People who co-used cannabis and nicotine/tobacco showed similar working memory performance, resting-state brain connectivity, and task-based brain activation compared to people without substance use. This suggests the two substances may offset each other's cognitive effects. Structural and molecular brain findings were inconsistent. Animal research was sparse but aligned with human memory findings.

Why it matters

Cannabis and tobacco are the most commonly co-used substances worldwide. Understanding that their combined effects on the brain may differ from either alone has implications for both treatment and risk assessment.

The numbers in context

39 studies reviewed; 4 databases searched; outcomes: cognition, brain structure, brain function, molecular markers; co-users showed similar working memory to non-users; structural findings inconsistent

How the study worked

Systematic review following PRISMA guidelines, searching four databases for human and animal studies examining associations between cannabis-nicotine/tobacco co-use and cognition, brain structure, brain function, and molecular outcomes. 39 studies were reviewed.

What this study cannot tell us

Heterogeneous study designs and measures across 39 studies. Cannot determine whether the offsetting effect is truly protective or reflects methodological confounds. Most studies were cross-sectional. Animal research was sparse.

How to read the evidence

Moderate: systematic review with PRISMA methodology covering 39 studies, but heterogeneous findings especially for structural and molecular outcomes.

When this study was published

2026 systematic review of human and animal studies on cannabis-tobacco co-use.

The bigger picture

This counterintuitive finding challenges the assumption that combining substances always worsens outcomes. If cannabis and nicotine partially compensate for each other's cognitive effects, cessation programs may need to consider the order and timing of quitting each substance.

Questions still open

Does the cognitive offsetting effect persist with long-term co-use? If someone quits one substance but not the other, do the protective effects disappear? Is the mechanism pharmacological (nicotine compensating for THC) or behavioral?

Common questions

Does using cannabis and tobacco together affect the brain differently than using just one?

Yes. This review found that people who use both showed cognitive performance and brain function similar to non-users, suggesting the two substances may partially cancel out each other's effects.

Does this mean co-use is safe?

No. The cognitive offsetting effect does not negate the respiratory, cardiovascular, or other health risks of both substances. The review also found inconsistent results for brain structure and molecular outcomes.

Read the original research

Cannabis and nicotine/tobacco co-use and its association with cognitive and neural outcomes: A systematic review.

Neuroscience and biobehavioral reviews, 180, 106480

View on PubMed ↗Publisher’s paper ↗

Citation

Yeap, Zac J S; Argote, Mathilde; Nadler, Emma; He, Pinning; Parvaz, Muhammad A; Rabin, Rachel A. (2026). Cannabis and nicotine/tobacco co-use and its association with cognitive and neural outcomes: A systematic review.. Neuroscience and biobehavioral reviews, 180, 106480. https://doi.org/10.1016/j.neubiorev.2025.106480