In a controlled trial of 28 healthy volunteers, a 1:1 CBD:THC ratio maximally reduced THC-induced psychotic symptoms and neural noise, while higher CBD doses provided no additional protection.
Read this if you choose cannabis products based on CBD:THC ratios and want to understand the science behind optimal ratios.
1:1 was bestThe lowest CBD:THC ratio maximally attenuated psychotomimetic effects; more CBD did not help
What the researchers found
The lowest CBD:THC ratio tested (1:1, using 2.5mg CBD with 0.035mg/kg THC) maximally attenuated both psychotomimetic effects (PANSS positive subscale) and "neural noise" — an electrophysiological biomarker of psychosis. Higher ratios (2:1 and 3:1) did not provide additional protection. Notably, no CBD dose reduced the subjective "high" from THC, suggesting CBD selectively blocks psychosis-relevant effects without eliminating intoxication.
Why it matters
This directly contradicts the assumption that more CBD always means more protection. The finding that the lowest ratio was most effective has major implications for cannabis product design and harm reduction strategies.
The numbers in context
- 28 healthy volunteers (12 women)
- CBD:THC ratios: 1:1, 2:1, 3:1
- 1:1 ratio: PANSS positive ATS=7.83, p_corrected=0.015
- 1:1 ratio: neural noise ATS=8.83, p_corrected=0.009
- No CBD dose reduced subjective "high" (p>0.05 for all)
How the study worked
Double-blind, randomized, placebo-controlled, counterbalanced human laboratory study. Intravenous THC with three CBD:THC ratios. EEG measurement of neural noise. PANSS for psychotomimetic symptoms. Subjective effects ratings.
Who was studied
28 healthy volunteers with at least one prior cannabis exposure
What this study cannot tell us
Small sample (n=28). Intravenous administration differs from typical cannabis use routes. Acute single-dose study. Very low absolute CBD doses (2.5-7.5mg) compared to commercial products.
How to read the evidence
Randomized double-blind placebo-controlled human laboratory study with both subjective and objective biomarkers. High-quality evidence.
When this study was published
Published in 2023. Provides critical dose-ratio data for CBD-THC interaction research.
The bigger picture
The non-linear, potentially inverted-U relationship between CBD dose and protection against THC-induced psychosis challenges both the "more CBD is better" marketing narrative and recent trial results showing no protection at higher ratios.
Questions still open
- Why does additional CBD beyond 1:1 lose protective efficacy?
- Would these results hold with inhaled or oral administration?
- Is there an optimal CBD:THC ratio for different therapeutic applications?
Read the original research
Delta-9-Tetrahydrocannabinol, Cannabidiol, and Acute Psychotomimetic States: A Balancing Act of the Principal Phyto-Cannabinoids on Human Brain and Behavior.
Cannabis and cannabinoid research, 8(5), 846-856
Citation
Ganesh, Suhas; Cortes-Briones, Jose; Schnakenberg Martin, Ashley M; Skosnik, Patrick D; D'Souza, Deepak C; Ranganathan, Mohini. (2023). Delta-9-Tetrahydrocannabinol, Cannabidiol, and Acute Psychotomimetic States: A Balancing Act of the Principal Phyto-Cannabinoids on Human Brain and Behavior.. Cannabis and cannabinoid research, 8(5), 846-856. https://doi.org/10.1089/can.2021.0166