Cannabidiol, also known as CBD, is one of the many active ingredients present in the cannabis plant. In 2018, cannabidiol (Epidiolex®) was approved in the US for the treatment of two rare forms of childhood epilepsy. Preclinical studies have suggested potential neuroprotective properties of cannabidiol, including improved cognitive functions and decreased inflammation. However, most clinical studies have shown a lack of cognitive improvement, and no data exist for long-term treatment in humans. Cannabidiol can affect the activity of many medications, and mild side effects are common, including liver problems and gastrointestinal issues.
Many clinical trials have been carried out, but no data exist for long-term treatment in healthy adults. Our search identified:
No studies have tested whether cannabidiol can prevent dementia or cognitive decline. In a double-blind randomized controlled trial of 27 healthy adults, cannabidiol treatment for 2 days did not have any significant effects on cognitive measures or mood . Clinical trials in schizophrenia patients also failed to show significant improvements in cognitive functions with cannabidiol treatment . Long-term studies are needed to evaluate the effects of cannabidiol on cognitive health.
Preclinical studies have shown that cannabidiol treatment prevents cognitive dysfunction in models of Alzheimer's disease , Parkinson's disease , memory impairment , and brain injury . Some proposed mechanisms include increased numbers of brain cells , increased levels of a protein (i.e., BDNF) that protects brain cells , decreased inflammation in the brain , and decreased levels of proteins that drive cell death .
Recreational use of cannabis seldomly causes permanent psychological disorders depending on the individual's sensitivity, including cognitive impairment, anxiety, paranoia, and increased risks of psychosis or drug addiction . Tetrahydrcannabinol (THC) appears to be responsible for many of these negative effects, while cannabidiol appears to counteract them .
No studies have tested cannabidiol specifically in dementia patients. Cannabidiol treatment prevents cognitive dysfunction in rodent models of Alzheimer's disease , but these benefits have not been confirmed in people with dementia. A randomized double-blind clinical trial showed that Nabilone, a synthetic cannabinoid, may be effective in treating agitation in people with Alzheimer's disease .
Cannabidiol may negatively affect liver function  and therefore, your doctor may monitor your liver enzyme levels before and during treatment . Other common side effects include drowsiness, decreased appetite, and gastrointestinal issues such as diarrhea . Cannabidiol interacts with many drugs, including anti-anxiety medications (e.g., citalopram, sertraline, alprazolam), anti-seizure medications (e.g., valproate), sleeping pills, opioid medications (e.g., buprenorphine, propoxyphene), lipid-lowering drugs (e.g., atorvastatin, lomitapide), blood thinners (e.g., clopidogrel), non-steroidal anti-inflammatory drugs (e.g., acetaminophen, diphenhydramine, naproxen), and drugs for multiple sclerosis (e.g., leflunomide, teriflunomide).
NOTE: This is not a comprehensive safety evaluation or complete list of potentially harmful drug interactions. It is important to discuss safety issues with your physician before taking any new supplement or medication.
Cannabidiol (sold as Epidiolex®) is available by prescription to treat two rare forms of childhood epilepsy. In seizure disorders, the initial dose is 2.5 mg/kg twice daily taken orally, then increased to 5 mg/kg twice daily . There are other cannabidiol-containing products on the market that are labeled as "dietary supplements," but the amount of cannabidiol contained is not always reported accurately on the product label and they may contain cannabis constituents other than cannabidiol .
More information on side effects is available on Drugs.com.
Check for drug-drug and drug-supplement interactions on Drugs.com.