Single dose of CBD increased blood flow to the hippocampus in healthy adults | Research

The takeaway

A 600mg dose of CBD significantly increased cerebral blood flow to the hippocampus, a key memory-processing region, in a small crossover trial of 15 healthy participants.

Researchers studying CBD mechanisms, people interested in CBD and brain health

CBD increased hippocampal blood flow with a medium-to-large effect size (d = 0.75)

What the researchers found

CBD increased cerebral blood flow in the hippocampus by an average of 15 mL/100g/min compared to placebo (Cohen's d = 0.75, p = 0.004). Greater CBD-induced increases in orbitofrontal CBF correlated with faster reaction times on a working memory task (r = -0.73, p = 0.005).

Why it matters

The hippocampus is central to memory formation, and showing that CBD increases blood flow there suggests a potential mechanism for CBD's therapeutic effects in conditions involving memory dysfunction.

The numbers in context

Hippocampal CBF increase: 15.00 mL/100g/min (95% CI: 5.78-24.21), Cohen's d = 0.75. Orbitofrontal CBF and 2-back reaction time correlation: r = -0.73, p = 0.005.

How the study worked

Randomized, crossover, double-blind design with 15 healthy participants receiving 600mg oral CBD or placebo on separate days. Cerebral blood flow measured at rest using arterial spin labelling MRI 3 hours after ingestion. Memory assessed via digit span, n-back, and prose recall tasks.

What this study cannot tell us

Very small sample (15 participants); single-dose design; no differences in actual memory task performance were detected; only healthy participants studied.

How to read the evidence

Small randomized crossover trial (n=15) with a single dose in healthy volunteers.

When this study was published

Published in 2020.

The bigger picture

These findings point to a possible mechanism by which CBD could influence conditions associated with altered memory processing, including Alzheimer's disease, PTSD, and schizophrenia.

Questions still open

Would repeated CBD dosing produce sustained changes in hippocampal blood flow? Would similar effects appear in people with memory-related conditions?

Common questions

Did CBD actually improve memory in this study?

No significant differences in memory task performance were found between CBD and placebo sessions. However, greater blood flow increases in one brain region did correlate with faster reaction times on a working memory task.

Why is increased hippocampal blood flow potentially important?

The hippocampus plays a central role in forming new memories. Several conditions involving memory dysfunction, such as Alzheimer's disease and PTSD, show altered hippocampal function, so increased blood flow there could be therapeutically relevant.

Read the original research

The effects of acute cannabidiol on cerebral blood flow and its relationship to memory: An arterial spin labelling magnetic resonance imaging study.

Journal of psychopharmacology (Oxford, England), 34(9), 981-989

View on PubMed ↗Publisher’s paper ↗

Citation

Bloomfield, Michael A P; Green, Sebastian F; Hindocha, Chandni; Yamamori, Yumeya; Yim, Jocelyn Lok Ling; Jones, Augustus P M; Walker, Hannah R; Tokarczuk, Pawel; Statton, Ben; Howes, Oliver D; Curran, H Valerie; Freeman, Tom P. (2020). The effects of acute cannabidiol on cerebral blood flow and its relationship to memory: An arterial spin labelling magnetic resonance imaging study.. Journal of psychopharmacology (Oxford, England), 34(9), 981-989. https://doi.org/10.1177/0269881120936419