Cannabidiol (CBD) is believed to affect memory in beneficial ways. There is evidence that CBD protects against potential impairments in memory caused by tetrahydrocannabinol (THC). [1,2,3] CBD has also demonstrated therapeutic possibility against disorders that intersect with memory, such as post-traumatic stress disorder (PTSD) , anxiety , and addiction . It has even been called a nootropic, purposed to boost cognitive performance and combat functional decline. However, less is known about how CBD exerts these effects.
Recently, a group of scientists from the University College of London investigated the how behind CBD’s impact on memory.  They explored cerebral blood flow (CBF), which describes the circulation of blood through veins and arteries in the brain. The researchers explained that “no study has investigated the association between regional CBF and memory task performance under acute CBD.”
Three hours prior to the CBF scans, fasting subjects (15) consumed capsules with either 600 mg CBD or a placebo. Researchers scanned brain areas associated with memory, including the hippocampus, amygdala, and orbitofrontal cortex (OFC). They also collected blood samples. After this (roughly 4.5–5.5 hours after consumption), the subjects performed a series of memory tests. These included prose recall (episodic memory), the N-back task (working memory), and digit span (working memory). All participants underwent both CBD and placebo trials (crossover design, 1-week washout).
Statistical analysis revealed that CBD caused a significant increase in CBF to the hippocampus. An increase was also observed in the OFC, but it failed to reach significance. The image below, reprinted from the open-access study, illustrates CBF in the hippocampus with the color scale indicating perfusion as mL/100 g/min.
Reprinted from: Bloomfield MAP, et al. 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. 2020;34(9):981-989. License: Creative Commons Attribution 4.0 International.
In general, CBD did not affect memory performance in otherwise healthy subjects. The exception was a significant correlation between CBD-induced blood flow to the OFC and one of the N-back tasks. Affected participants reacted faster. The authors reason that “the OFC is involved in [working memory], particularly emotion and/or face processing working memory.”
Ultimately, they conclude that “higher resting hippocampal blood flow is associated with better memory performance,” which could have major implications for disorders affecting the hippocampus. These include, among others, Alzheimer’s disease.  Even so, the precise mechanisms governing CBD’s effects on memory remain to be elucidated.
- Bloomfield MAP, et al. 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. 2020;34(9):981-989.
- Schoeler T, Bhattacharyya S. The effect of cannabis use on memory function: an update. Subst Abuse Rehabil. 2013;4:11-27. doi:10.2147/SAR.S25869
- Hindocha C, et al. Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: A randomised, double-blind, placebo-controlled study in cannabis users. Eur Neuropsychopharmacol. 2015;25:325–334.
- Elms L, et al. Cannabidiol in the treatment of post-traumatic stress disorder: A case series. J Altern Complement Med. 2018;25(4):392-397. doi:10.1089/acm.2018.0437
- Blessing EM, et al. Cannabidiol as a potential treatment for anxiety disorders. Neurotherapeutics. 2015;12(4):825-836. doi:10.1007/s13311-015-0387-1
- Knopf A. CBD may help prevent relapse in abstinent heroin addicts. Alcoholism & Drug Abuse Weekly. 2019;31:3-4. doi:10.1002/adaw.32382