The primary aim was to investigate how CBD influences cerebral blood flow (CBF) in regions involved in memory processing. It was conducted under a randomised, crossover, double-blind design in which 15 healthy participants were administered CBD or a placebo on separate days. Regional CBF was measured at rest using arterial spin labelling 3h after drug ingestion. Working memory was assessed with the digit span (forward, backward) and n-back (0-back, 1-back, 2-back) tasks, and a prose recall task was used (immediate and delayed) to assess episodic memory.
CBD increased CBF in the hippocampus (mean (95% confidence intervals) = 15.00 (5.78–24.21) mL/100 g/min, t14 = 3.489, Cohen’s d = 0.75, p = 0.004). There were no differences in memory task performance, but there was a significant correlation whereby greater CBD-induced increases in orbitofrontal CBF were associated with reduced reaction time on the 2-back working memory task ( r= −0.73, p = 0.005).
This may be the first study to find that acute CBD increases CBF in the hippocampus. This supports the view that CBD has region-specific haemodynamic effects in the human brain. If replicated, the finding that acute CBD increases CBF in the hippocampus may be relevant for hippocampal disorders, since higher resting hippocampal blood flow is associated with better memory performance, although this relationship is not entirely clear. With its key role in learning and memory, the hippocampus is an important therapeutic target across multiple neuropsychiatric disorders including Alzheimer’s disease.
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