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What is CBD (Cannabidiol)?
What is CBD?

CBD and THC are the two primary active ingredients in marijuana.

You may be familiar with the most prominent and well-known components of cannabis: THC. THC has many effects on the body, and is the compound responsible for getting you high when you consume cannabis. CBD, on the other hand, is less present in cannabis. CBD has its own effects on the body, and is becoming increasingly popular for medical uses.

Here we explore the history, effects, controversy and scientific knowledge behind CBD.

What is CBD?

Chemical structure of cannabidiol
Chemical structure of cannabidiol (Photo: Wikimedia Commons)

Cannabidiol (CBD) is one of over 100 naturally-occurring cannabinoids in the cannabis plant. After THC, it is the most prominent component of cannabis and is found most readily in hemp.

Unlike THC, CBD does not produce a “high” that cannabis use is known for. It is therefore generally used more for medicinal rather than recreational purposes.


Although cannabis use has been documented as far back as 2727 B.C.E.1, it wasn’t until the 1940s that chemist Roger Adams first isolated CBD from the cannabis plant2.

In the 1960s, Raphael Mechoulam defined the structures of CBD and THC more precisely with the help of newly available technology3.

Over the next few decades, evidence emerged that cannabis could be used to treat symptoms of arthritis, epilepsy, anxiety, and schizophrenia sparking interest among scientists and doctors.

Legal status

In the United States, cannabis is listed as a Schedule I drug, meaning cannabis possession, use, sale, cultivation and transportation is illegal27.

Recreational and medical use is legal in Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon and Washington. Over 90% of states have also legalized cannabis use for medical purposes28,29.

Hemp stalk (or agricultural hemp) is not included in the legal definition of cannabis, so some producers extract CBD from the stalk and market it as a legal product.

Careful interpretation of the DEA’s statement on marijuana extracts from December 201630,31, however, suggests that this practice is also illegal32.

How CBD Works

How CBD Works
(Photo: Shutterstock)

Cannabis flowers are not soluble in water, so they do not produce any effect when consumed directly.

CBD is fat-soluble, meaning that it can be administered in oils and butters. CBD oils can be ingested directly, vaporized or put into pill form.

CBD oil can also be added into recipes while cooking to make a CBD-infused food. Because CBD is fat-soluble, it can also enter the brain.

The endocannabinoid system

Once in the body, cannabinoids like CBD are processed by the endocannabinoid system. This system involves chemical messaging in the brain and body via cannabinoid receptors33.

Cannabinoid receptor 1 (CB1) is found mostly in the brain and nervous system, while cannabinoid receptor 2 (CB2) is found mostly in other organs of the body.

These receptors influence pain sensation, mood, appetite, movement and memory, and can be acted on by 3 classes of cannabinoids:

• Endocannabinoids: produced by the body
• Phytocannabinoids: produced by plants such as marijuana e.g. CBD
• Synthetic cannabinoids: created in a laboratory

How CBD works in the body

THC is a partial agonist of the CB1 and CB2 receptors, meaning that it weakly activates those receptors34.

CBD also acts on both CB1 and CB2 receptors, but less readily than THC and in different ways, producing an opposite response at the CB2 receptor than THC35.

Along with cannabinoid receptors, CBD activates serotonin receptors, which may explain how it works as an antidepressant, anti-anxiety and neuroprotective substance36.

CBD also acts on some types of opioid receptors, which could potentially underlie some of its pain-relieving effects37.

CBD also modulates Transient Vanilloid Receptor type 1 (TPVR-1), a receptor that is activated by the spicy-food molecule capsaicin, potentially further implicating CBD as an analgesic and anti-inflammatory38.

Recently, a new cannabinoid receptor called GPR55 was identified in brain areas related to reward. CBD has been found to act on this receptor, and will likely shed more light on how CBD exerts its actions in the body39.

Once CBD has exerted its effects on the body, it is mostly excreted through in the urine. The half-life (time it takes for the dose of a drug to be reduced by half) of CBD is 9 hours40.

CBD + THC interaction

The combination of THC and CBD is more complex than simply taking the sum of effects of CBD and THC. CBD can slow clearance of THC from the body, thus increasing the amount of THC that remains in the body.

There is also some evidence that CBD blocks the action of THC on the CB1 receptor, effectively helping to curb the paranoia or anxiety that can be experienced from using THC41.

The relative levels of THC and CBD within a strain of cannabis or an extract are important.

A high THC to CBD ratio (levels of THC compared to CBD) will produce more of a “high” feeling for the user, and provide therapeutic benefit for some people. A low THC to CBD ratio yields more therapeutic effects and virtually no “high”42.

Entourage effect

In addition to THC and CBD, the cannabis plant is composed of many other cannabinoids, terpenes and flavonoids. Researchers don’t yet know the effects of each component, and exactly how they interact with each other.

There is evidence, however, that suggests that these compounds work better together than on their own in what’s known as the “entourage effect”43.

Some believe that the greatest therapeutic benefits come from taking plant sources that preserve the entourage effect rather than using extracts or synthetic compounds.

Interactions with other drugs

Among many therapeutic effects, CBD is also known to inhibit the cytochrome P-450 enzyme system, a system in the liver that breaks down many commonly prescribed drugs44.

Because CBD inhibits this system, the metabolism of drugs that rely on this pathway may be slowed down when also taking CBD.

Interaction effects can vary greatly between people, so it is always recommended that you speak with your doctor before adjusting the combination or dosage of any medications you are taking.

Effects of CBD

Medical Marijuana
(Photo: Gordon Swanson/Shutterstock)


CBD has been reported to have many benefits to people suffering from a wide range of symptoms and conditions45:

  • Neuroprotective
  • Pain relief
  • Relieves anxiety
  • Antidepressant
  • Lowers blood pressure
  • Antioxidant
  • Reduces cancer cell growth
  • Reduces inflammation

Although there are many reports of people benefitting from CBD in a variety of ways, the mechanisms of action underlying these effects are still widely unknown.

Medical Uses

The scientific study of CBD is still new, but researchers are looking at the potential for CBD as a treatment for many different diseases, some of which are listed below:

  • Alzheimer’s Disease- anti-inflammatory, antioxidant, prevents cell death in cell and animal models of Alzheimer’s47
  • Anxiety- reduces muscular tension, restlessness, fatigue and concentration problems48
  • Cancer- may have protective effects in breast cancer, slows growth of many other types of cancer49
  • Cardiovascular disease- reduces size of damaged area via antioxidant and anti-inflammatory properties in cell and animal models50
  • Chron’s disease and Inflammatory bowel disease- reduction in disease activity51
  • Depression- Anti-depressant in genetic rodent model of depression, some human evidence as well52
  • Diabetes- Improved secondary effects on the heart (heart attack, fibrosis)53
  • Digestion- stimulates appetite, an important factor for those suffering from illnesses that decrease appetite54
  • Epilepsy- Anticonvulsant, reduction in seizures for both children and adults with treatment-resistant epilepsy55
  • Huntington’s Disease- Neuroprotective, antioxidant in mice, no current observed benefits to humans56
  • Hypoxia-Ischemia Injury- Short term neuroprotective effects, inhibition of oxidative stress and inflammation in rodent models57
  • Inflammatory disease- Anti-inflammatory in cell and animal models, inhibition of cellular inflammatory pathways58
  • Infection- Activity against methicillin-resistant Staphylococcus aureus (antibiotic- resistant MRSA)59
  • Nausea and Vomiting –  Effective against chemotherapy and other therapy-induced nausea, suppression of nausea in rats60
  • Multiple Sclerosis- Anti-inflammatory and immunomodulation in mice61
  • Pain- Analgesic for patients with treatment-resistant neuropathic pain62
  • Parkinson’s Disease- Attenuation of dopaminergic impairment in animal models, neuroprotection, reduced agitation, nightmares and aggressive behaviour in humans63
  • Rheumatoid Arthritis- Inhibition of TNF-a in animal models (a protein involved in inflammation)64
  • Schizophrenia- Relief from psychotic symptoms65
  • Social Anxiety- Improved social interactions in rodent models of anxiety and stress, reduced social anxiety in humans66

Safety and Side Effects

Cannabis prescription
(Photo: poylock19/Shutterstock)

How safe is CBD?

CBD is generally considered very safe. It is non-psychoactive and does not alter motor function or memory. It has very low toxicity, with no documented properties that lead to damage of DNA.

However, some studies have shown that CBD can slow the metabolism of drugs that pass through the liver72. It is important to talk to your doctor about potential interactions between CBD and any drugs or supplements you are taking.

There are some animal studies that have demonstrated that CBD can decrease fertility, but reports of the opposite in humans73.

One study found that very high doses of CBD (above 200mg per kg of body weight) were toxic to lethal levels in some monkeys after causing respiratory failure and cardiac arrest74.

Dosing information

CBD has been prescribed for many patients67. Some examples of dosing for specific disorders can be found below:

CBD products have been used by many patients with various conditions. According to the Mayo Clinic, CBD may be taken in the following dosages:

Increase appetite – 1mg CBD by mouth (with 2.5mg THC) for 6 weeks

Chronic pain – CBD doses ranging from 2.5-20mg for average of 25 days

Epilepsy – 200-300mg by mouth daily for 4.5 months

Huntington’s Disease – 10mg/kg by mouth for 6 weeks

Sleep disorders – 40-160mg by mouth

Multiple Sclerosis – 2.5mg-120mg Sativex (2.5mg CBD / 2.7mg THC) for up to 8 weeks

Schizophrenia – 40-1280mg by mouth for 4 weeks

Rheumatoid arthritis – 6 sprays Sativex (2.5mg CBD / 2.7mg THC) daily before bed

Glaucoma – 20-40mg CBD under the tongue (Note: 40mg of CBD or more may increase eye pressure)

Without a prescription, there are other ways to figure out what dose of CBD may work best for you68.

Is CBD safe for children?

Most information regarding the safety of CBD use in children is anecdotal75. Many parents report that CBD has treated their children’s epilepsy in unprecedented ways, and some doctors have started prescribing CBD to kids for this purpose76,77.

However, no formal research has been conducted on the safety of long-term CBD use in children78. There is currently no good understanding of the developmental effects of CBD, although THC has been shown to negatively impact development79.

The use of any pharmaceutical comes with risks to be weighed against any potential benefits. Although there still isn’t scientific evidence for the safety of CBD use in kids, for many parents, the relief that CBD gives their children is nothing short of miraculous.

Is CBD safe for pets?

Unlike THC, there are no reports that CBD has any toxic effects in dogs. The metabolism of CBD in humans and dogs is reported to be largely similar80, but there are some small differences in the by-products of the CBD breakdown process. Neither the short- or long-term effects of these differences are well known.

Dog treats containing CBD have been used to treat pain and inflammation resulting from cancer, arthritis and epileptic seizures. Some owners have also reported that CBD helps their dogs with separation anxiety, fear of thunderstorms, fireworks, car rides, visits to the vet and anxiety around other animals81. CBD treats have also been used to increase appetite in animals suffering from serious health problems.

Hemp seed oil has been developed as a supplement to thicken fur, reduce shedding and prevent dandruff in dogs based on essential fatty acids found in hemp oil82.

Although less popular than use in dogs, there is some reported use of hemp products in cats to treat cancer, anxiety and arthritis83.

Despite some people claiming benefits of CBD use in pets84, safe and effective CBD dosages have not been established. If you believe that your pet would benefit from CBD, it is always recommended that you speak with your veterinarian before giving your pet any supplements.