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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.
Keywords: Cannabis (marijuana); cannabidiol; delta9-tetrahydrocannabinol; functional MRI; neuroimaging.
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.
CB1 and CB2 are the main cannabinoid receptors, though scientists are confident that there are more. CB1 receptors are mainly found in the central nervous system (CNS). They help regulate mood, pain, coordination, and other crucial functions. CB2 receptors are primarily in the immune system. They have an impact on inflammation and pain.
CBD is one of over 110 cannabinoids produced by cannabis. It is also abundant in the hemp plant. THC is famed for its ability to cause an intoxicating high. In contrast, CBD is non-intoxicating. Nonetheless, there is evidence that both compounds have possible therapeutic effects. This is part of the reason why CBD for sale is now an exciting proposition.
CBD’s impact on CB2 receptors may help reduce oxidative stress. Cannabidiol also appears to have antioxidant properties. According to a study published in the Journal of Alzheimer’s Disease in 2014, CBD products’ long-term usage led to antioxidative and anti-inflammatory effects.
The Difference in How THC & CBD Impact Receptors
In contrast, CBD has a significantly less potent effect on the ECS’s receptors. It only binds loosely to CB1 receptors. This action actually blocks the receptors, thus reducing the effects of THC.
Unfortunately, an excessive level of free radicals could result in the loss of DNA particles. This is especially the case if the body doesn’t create enough antioxidants. This process is linked to medical conditions such as Parkinson’s and Alzheimer’s.
Relatively few people have heard about the process of excitotoxicity in the brain, yet it plays a huge role in neurodegenerative diseases. It is a term used to describe the damage caused when the brain cells become excessively active due to too much stimulation. Excitotoxicity can happen after a stroke, traumatic brain injury, or even hearing loss.
There is also a possibility that CBD reduces oxidative stress, which occurs at the cellular level. Cells produce free radicals whenever they generate energy. Environmental toxins also produce this waste product. The body utilizes antioxidants to deal with free radical production and ensure the damage they cause is minimized.