Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test.
This trial found only the 300 mg dose helped — 150 mg and 600 mg did nothing — so how would I know whether any over-the-counter CBD product is anywhere near a dose that has ever been tested?
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: The disclosure states that STI-Pharm supplied the CBD at no cost and that four authors are co-inventors of a fluorinated-CBD patent; the University of São Paulo has licensed that patent and holds an agreement with Prati-Donaduzzi to develop a synthetic CBD product for indications including anxiety disorders. Public grant money plus donated study drug and patent interests is why funding is recorded MIXED.
One cannabidiol product is FDA-approved: Epidiolex (plant-derived purified CBD oral solution), indicated for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, or tuberous sclerosis complex in patients 1 year and older.
Fifty-seven healthy men were randomised to 150 mg, 300 mg, or 600 mg of oral CBD or placebo before a simulated public speaking test. Only the 300 mg dose significantly reduced anxiety; 150 mg and 600 mg were no different from placebo. More CBD is not better, and the dose that worked here is far above what retail CBD products deliver.
Worth asking
This trial found only the 300 mg dose helped — 150 mg and 600 mg did nothing — so how would I know whether any over-the-counter CBD product is anywhere near a dose that has ever been tested?
Source
Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test. — Linares IM, Zuardi AW, Pereira LC, et al. (2019)
Reputable peer-reviewed journal
Read the source: https://doi.org/10.1590/1516-4446-2017-0015
DOI: 10.1590/1516-4446-2017-0015
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Mixed public and industry funding
- Published in
- Reputable peer-reviewed journal
- Sample size
- 57
- Preregistered
- No
- Conflicts disclosed
- Yes
- Independent of proponent
- No
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Where we put this study in context
Questions
How strong is the evidence behind this?
Resolv rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 58 out of 100 on our published rubric. One caveat travels with that badge: The disclosure states that STI-Pharm supplied the CBD at no cost and that four authors are co-inventors of a fluorinated-CBD patent; the University of São Paulo has licensed that patent and holds an agreement with Prati-Donaduzzi to develop a synthetic CBD product for indications including anxiety disorders. Public grant money plus donated study drug and patent interests is why funding is recorded MIXED. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Cannabidiol presents an inverted U-shaped dose-response curve in a simulated public speaking test. — Linares IM, Zuardi AW, Pereira LC, et al. (2019). Published in: Reputable peer-reviewed journal. DOI: 10.1590/1516-4446-2017-0015. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Mixed public and industry funding. The researchers were not independent of whoever benefits from the result. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is cannabidiol, cbd, hemp extract, cbd oil, epidiolex, full-spectrum hemp FDA approved for this use?
No. Its current status is: Not FDA-evaluated for this use. One cannabidiol product is FDA-approved: Epidiolex (plant-derived purified CBD oral solution), indicated for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, or tuberous sclerosis complex in patients 1 year and older.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.