In a naturalistic study using legal-market cannabis, THC impaired verbal recognition memory as expected—but adding CBD didn't provide the protective effect that some earlier research had suggested.
Cannabis consumers choosing products by THC:CBD ratio, harm reduction advocates, and researchers studying cannabinoid interactions.
What the researchers found
The idea that CBD might counteract THC's cognitive effects has been a popular hypothesis in cannabis research—and a selling point for balanced THC:CBD products. This study put it to a direct test using legal-market flower.
One hundred sixteen participants were randomly assigned to one of three strains: THC-dominant, roughly 1:1 THC:CBD, or CBD-dominant. They completed verbal recognition memory tasks in two sessions (baseline and after use), allowing within-person comparison.
THC impaired verbal memory accuracy, consistent with decades of prior research. The key question was whether adding CBD would buffer that effect. It did not. The 1:1 THC:CBD strain produced memory impairment similar to the THC-dominant strain—no protective CBD effect was observed.
The CBD-dominant strain, predictably, showed the least memory impact. But this isn't because CBD protected against THC—it's because the CBD-dominant strain contained very little THC to begin with.
This is one of the first studies to test the CBD-protection hypothesis with legal-market products rather than lab-controlled preparations, making it more generalizable to real-world use. The null finding for CBD protection is important for consumers choosing products based on the belief that balanced ratios are cognitively safer.
Why it matters
Many consumers choose 1:1 THC:CBD products specifically because they believe CBD will protect against THC's cognitive effects. This study found no evidence for that protective effect on verbal memory, which is one of THC's most reliable cognitive impacts. If the protection hypothesis doesn't hold for the most well-documented cognitive effect, it may not hold for other effects either.
The numbers in context
N = 116 (40 THC-dominant, 38 1:1 THC:CBD, 38 CBD-dominant). THC reduced verbal recognition memory accuracy. 1:1 THC:CBD strain did not protect against THC's memory effects. CBD-dominant strain showed least impairment.
How the study worked
Naturalistic observational study. 116 participants randomly assigned to three legal-market flower strains: THC-dominant (n=40), 1:1 THC:CBD (n=38), or CBD-dominant (n=38). Two experimental sessions with verbal recognition memory testing before and after cannabis use.
Who was studied
N=116 adults aged 18-65, 54% female, using legal cannabis products in the US.
What this study cannot tell us
Naturalistic design means participants used cannabis in their normal setting (less control than a lab). Flower products vary batch-to-batch in actual cannabinoid content. Only verbal recognition memory tested—CBD might protect other cognitive domains. The 1:1 ratio is one specific balance; other ratios might behave differently. Acute effects only—chronic use patterns weren't examined.
How to read the evidence
Randomized assignment to legal-market strains with within-person comparison—stronger than most naturalistic designs, though less controlled than lab-based studies.
When this study was published
Published in 2025 using legal-market products, reflecting what consumers actually purchase.
The bigger picture
This challenges a finding cited in several earlier studies and adds nuance to RTHC-00155's alcohol + cannabis memory data. RTHC-00155 found sex differences in memory effects from combining cannabis and alcohol; this study tests whether the cannabis formulation itself (specifically the THC:CBD ratio) moderates memory effects. The answer—at least for recognition memory—appears to be no. This has implications for harm reduction strategies that recommend balanced strains.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Does CBD protect against THC effects on other cognitive domains (executive function, attention) even if not on memory? Would very high CBD doses relative to THC show a protective effect? Should harm reduction messaging about balanced strains be revised?
Read the original research
Naturalistic investigation of cannabis strains varying in THC and CBD ratios and verbal recognition memory.
Frontiers in psychology, 16, 1685412
Frontiers in Psychology is a reputable journal focusing on psychological research and its applications.
Citation
Paulich, Katie N; Place, Christian; Giordano, Gregory; Carpenter, William B; Curran, Tim; Bidwell, L Cinnamon. (2025). Naturalistic investigation of cannabis strains varying in THC and CBD ratios and verbal recognition memory.. Frontiers in psychology, 16, 1685412. https://doi.org/10.3389/fpsyg.2025.1685412
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