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the effects of cbd on the brain

Keywords: Cannabis (marijuana); cannabidiol; delta9-tetrahydrocannabinol; functional MRI; neuroimaging.

Copyright © 2021 Batalla, Bos, Postma and Bossong.

Background: Accumulating evidence suggests that the non-intoxicating cannabinoid compound cannabidiol (CBD) may have antipsychotic and anxiolytic properties, and thus may be a promising new agent in the treatment of psychotic and anxiety disorders. However, the neurobiological substrates underlying the potential therapeutic effects of CBD are still unclear. The aim of this systematic review is to provide a detailed and up-to-date systematic literature overview of neuroimaging studies that investigated the acute impact of CBD on human brain function. Methods: Papers published until May 2020 were included from PubMed following a comprehensive search strategy and pre-determined set of criteria for article selection. We included studies that examined the effects of CBD on brain function of healthy volunteers and individuals diagnosed with a psychiatric disorder, comprising both the effects of CBD alone as well as in direct comparison to those induced by ∆9-tetrahydrocannabinol (THC), the main psychoactive component of Cannabis. Results: One-ninety four studies were identified, of which 17 met inclusion criteria. All studies investigated the acute effects of CBD on brain function during resting state or in the context of cognitive tasks. In healthy volunteers, acute CBD enhanced fronto-striatal resting state connectivity, both compared to placebo and THC. Furthermore, CBD modulated brain activity and had opposite effects when compared to THC following task-specific patterns during various cognitive paradigms, such as emotional processing (fronto-temporal), verbal memory (fronto-striatal), response inhibition (fronto-limbic-striatal), and auditory/visual processing (temporo-occipital). In individuals at clinical high risk for psychosis and patients with established psychosis, acute CBD showed intermediate brain activity compared to placebo and healthy controls during cognitive task performance. CBD modulated resting limbic activity in subjects with anxiety and metabolite levels in patients with autism spectrum disorders. Conclusion: Neuroimaging studies have shown that acute CBD induces significant alterations in brain activity and connectivity patterns during resting state and performance of cognitive tasks in both healthy volunteers and patients with a psychiatric disorder. This included modulation of functional networks relevant for psychiatric disorders, possibly reflecting CBD’s therapeutic effects. Future studies should consider replication of findings and enlarge the inclusion of psychiatric patients, combining longer-term CBD treatment with neuroimaging assessments.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

THC closely mimics a naturally occurring cannabinoid named anandamide which binds to the CB1 receptors, which are responsible for many of THC’s psychoactive effects. As the psychoactive cannabinoid binds to anandamide’s CB1 receptors even more closely than anandamide, which is known as ‘the bliss molecule.’ It inhibits the release of other neurotransmitters. This helps explain the feelings of euphoria associated with the ‘high’ from cannabis.

However, we still need further clinical trials involving humans to confirm CBD’s positive neurological effects.

Understanding CBD

The cannabinoid’s effects on the brain appear to be many and profound, but we need more confirmatory studies. We advise all readers to steer clear of CBD sellers that try to portray cannabidiol as a ‘cure-all.’ There is no question that the existing research is exciting, but it would be irresponsible to draw too many conclusions just yet.

A study by Cheng et al., published in the Journal of Alzheimer’s Disease in 2014, found that long-term CBD treatment “prevents the development of social recognition memory deficits in Alzheimer’s disease transgenic mice.” The researchers also wrote that CBD exerts anti-inflammatory, antioxidative, and neuroprotective properties in vitro and in vivo.

CBD’s antipsychotic effects relate to its impact on anandamide. Scientists link higher levels of the bliss molecule with a decrease in psychotic symptoms. A study by Leweke et al. published in Translational Psychiatry in March 2012, looked into the effect of CBD on anandamide production.