Tobacco and Cannabis Smoke Are Both Linked to Lower Dopamine Receptor Levels
People who tested positive for tobacco and/or cannabis metabolites had 13% lower striatal dopamine D2 receptor availability on PET imaging, particularly in the nucleus accumbens and putamen.
Quick Facts
What This Study Found
Individuals positive for urine metabolites of tobacco and/or cannabis had an average 13.1% lower D2 receptor availability across all striatal subregions compared to negative individuals, with the most significant differences in reward-related brain areas.
Key Numbers
29 participants. 13.1% average lower D2 BPND in analyte-positive group (range: 6.6-20.0%). Significant differences in nucleus accumbens and putamen. No effects of alcohol use disorder.
How They Did This
Cross-sectional PET imaging study using [11C]raclopride in 29 participants, comparing striatal D2 receptor availability between those with quantified positive vs. negative urine metabolites for nicotine (cotinine) and THC (THCA).
Why This Research Matters
Lower D2 receptors in reward circuits are associated with addiction vulnerability and reduced reward sensitivity. Finding that both tobacco and cannabis smoke lower D2 availability suggests shared mechanisms of combustible smoke impact on the brain's reward system.
The Bigger Picture
This study uniquely uses objective biomarkers (urine metabolites) rather than self-report to classify smoke exposure, revealing that combustible smoke products — regardless of source — may share neurotoxic effects on dopamine systems.
What This Study Doesn't Tell Us
Very small sample of 29. Cross-sectional design cannot determine if low D2 preceded or resulted from substance use. Cannot separate tobacco from cannabis effects within the positive group.
Questions This Raises
- ?Do non-combusted cannabis products (edibles, vapes) also affect D2 receptors?
- ?Are the D2 changes reversible with smoking cessation?
Trust & Context
- Key Stat:
- Evidence Grade:
- Novel use of biomarker-verified exposure improves on self-report studies, but very small sample limits confidence in the findings.
- Study Age:
- Recent study introducing objective metabolite verification to PET imaging research on substance effects on dopamine systems.
- Original Title:
- Lower striatal dopamine D2 receptor availability in individuals who test positive for quantitated urine metabolites of tobacco and/or marijuana smoke.
- Published In:
- Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco (2025)
- Database ID:
- RTHC-08003
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Does smoking cannabis lower dopamine receptors?
This small PET study found 13% lower D2 receptor availability in people positive for tobacco and/or cannabis metabolites. The study couldn't separate the effects of each substance, but both involve combustible smoke.
What does lower D2 availability mean?
D2 receptors are part of the brain's reward system. Lower availability may mean reduced reward sensitivity, which is associated with seeking more intense stimulation and potentially addiction vulnerability.
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Cite This Study
https://rethinkthc.com/research/RTHC-08003APA
Yoder, Karmen K; Carpenter, Samantha; Hile, Karen L; Dzemidzic, Mario; Durazzo, Timothy C. (2025). Lower striatal dopamine D2 receptor availability in individuals who test positive for quantitated urine metabolites of tobacco and/or marijuana smoke.. Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco. https://doi.org/10.1093/ntr/ntaf249
MLA
Yoder, Karmen K, et al. "Lower striatal dopamine D2 receptor availability in individuals who test positive for quantitated urine metabolites of tobacco and/or marijuana smoke.." Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco, 2025. https://doi.org/10.1093/ntr/ntaf249
RethinkTHC
RethinkTHC Research Database. "Lower striatal dopamine D2 receptor availability in individu..." RTHC-08003. Retrieved from https://rethinkthc.com/research/yoder-2025-lower-striatal-dopamine-d2
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.