In less-frequent cannabis users, both THC and CBD increased mismatch negativity brain responses, but adding low-dose CBD to THC attenuated this effect, with different patterns in frequent versus less-frequent users.
Neuroscience researchers studying cannabinoid effects on brain function and psychosis biomarkers.
CBD attenuated THC effects on brain biomarkers, varying by use history
What the researchers found
THC and CBD both increased duration and intensity MMN amplitude in less-frequent users. Low-dose CBD added to THC attenuated THC's effect on duration and intensity MMN in less-frequent users. High-dose CBD added to THC had similar attenuating effects in frequent users. The pattern of effects varied as a function of prior cannabis exposure.
Why it matters
MMN is a candidate biomarker for schizophrenia linked to NMDA receptor function. Understanding how cannabinoids affect this marker helps clarify the complex relationship between cannabis and psychosis.
The numbers in context
36 participants (18 frequent, 18 less-frequent users). 5 drug conditions. THC 8mg and CBD 400mg both increased MMN in less-frequent users. Low CBD (4mg) with THC attenuated effects in less-frequent users.
How the study worked
Randomized, double-blind, crossover placebo-controlled study with 18 frequent and 18 less-frequent cannabis users. Five vaporized drug sessions: placebo, THC 8mg, CBD 400mg, THC 8mg+CBD 4mg, THC 12mg+CBD 400mg. Multifeature MMN paradigm with duration, frequency, and intensity deviants.
What this study cannot tell us
Small sample (36 total). Acute effects may not reflect chronic use patterns. MMN changes may not directly relate to clinical outcomes or psychosis risk.
How to read the evidence
Rigorous double-blind crossover design with neurophysiological measures, but very small sample.
When this study was published
Published in 2022.
The bigger picture
The finding that CBD can modify THC's effects on brain biomarkers, but differently depending on use history, highlights the complexity of cannabinoid interactions and the importance of individual differences.
Questions still open
- Do these acute neurophysiological effects predict long-term psychosis risk? What CBD:THC ratio optimally modulates brain responses?
Common questions
What is mismatch negativity?
Did CBD protect against THC effects?
Read the original research
Acute effects of Δ9-tetrahydrocannabinol and cannabidiol on auditory mismatch negativity.
Psychopharmacology, 239(5), 1409-1424
Citation
Greenwood, Lisa-Marie; Broyd, Samantha J; van Hell, Hendrika H; Todd, Juanita; Jones, Alison; Murray, Robin M; Croft, Rodney J; Michie, Patricia T; Solowij, Nadia. (2022). Acute effects of Δ9-tetrahydrocannabinol and cannabidiol on auditory mismatch negativity.. Psychopharmacology, 239(5), 1409-1424. https://doi.org/10.1007/s00213-021-05997-3
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