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The rise in interest in CBD has led to a plethora of CBD based products flooding the health market.
Medical versus popular opinion can be divided on whether CBD is of use in health or not.
In this article we take a look at the evidence behind CBD and certain health conditions.
What is CBD?
CBD is short for cannabiodiol and is one of over 100 compounds, called cannabinoids, that are found in the cannabis plant.
Unlike another commonly known cannabinoid, THC, CBD does not have psychoactive effects.
This means it won’t cause a ‘high’ that is associated with using marijuana.
How CBD is Thought to Work
CBD is claimed to be beneficial for a vast amount of very different conditions, usually when this occurs it evokes scepticism and disbelief: how can one compound affect the whole body?
The way in which CBD is thought to work is through interacting with the endocannabinoid system.
The endocannabinoid system in the body involves naturally produced fat soluble cannabinoids, such as anandamide and 2-AG, which can act on specific receptors in the body and brain to give an effect.
These receptors, CB1 and CB2, are distributed throughout the body and the brain. CB1 receptors are mainly found in the brain and spinal cord but are also present in the reproductive, urinary and GI tract.
CB2 receptors are mostly concentrated in immune cells and some nerve cells (1).
Each receptor may respond to different cannabinoids or may be influenced by many cannabinoids.
The endocannabinoid system is known to influence several functions in the body and can play a role in:
- Metabolism
- Mood
- Sleep
- Reward and pleasure
- Appetite
- Memory and learning
- Pain
- Inflammation
- Immune function
- Cardiovascular function
- Digestion
- Reproduction and fertility
- Nerve protection
Whilst some people believe that CBD has a mild ability to bind to CB1 and CB2 receptors, others think that its effects come from inhibiting enzymes that directly breakdown the natural endocannabinoids, like anandamide, therefore increasing their levels (2).
It has also been shown that CBD may act on other receptors in the body which play a role in mood and anxiety (3) and pain and inflammation (4).
This may explain why CBD is gaining popularity for a wide range of health conditions.
CBD in Health
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Epilepsy
The evidence for the use of cannabis derived compounds such as CBD is well established in cases of epilepsy.
In fact, CBD is available as prescription medicine for the treatment of epilepsy (5).
The mechanism behind the benefits of CBD in epilepsy isn’t fully known but it is thought to be due to CBD having neuroprotective effects.
One study showed that CBD reduced the toxicity of the major excitatory neurotransmitter glutamate (7).
CBD was first used to treat children with severe forms of epilepsy, such as Dravet syndrome and Lennox-Gastaut syndrome (LGS).
These types of epilepsy are hard to manage and often resistant to traditional anti-seizure medications.
CBD may not only reduce seizures but also improve behaviour, alertness, communication and sleep (8,9).
Professional guidance on use in epilepsy is always advisable, particularly as some interactions with anti-seizure medications may occur (10).
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Neurodegenerative Conditions
The development of neurodegenerative conditions is complex and often involves many factors.
Parkinson’s is characterised by a loss of motor function and gives classic signs of shaking, rigidity and slowing of movements.
The neuroprotective effects of CBD may be down to a reduction in oxidative stress (11).
Oxidative stress occurs when the body is overwhelmed by damaging molecules called free radicals.
Studies also show that symptoms associated with Parkinson’s such as psychosis or sleep related issues may also benefit from CBD use (12,13). An improvement in quality of life is also reported (14).
Alzheimer’s affects around three quarters of a million people in the UK.
It involves neuroinflammation and oxidative stress – current treatment unfortunately does not slow or stop progression of the disease.
Studies in animal models of Alzheimer’s show that CBD has anti-inflammatory, neuroprotective and antioxidant activities (15).
Data from animal studies also indicate that some cognitive abilities may be preserved or in some cases returned (16).
Research into the use of CBD in Alzheimer’s is ongoing and further human studies may give a clearer indication of the potential benefits of CBD in Alzheimer’s.
Like other neurodegenerative conditions, multiple sclerosis involves neuro-inflammation and it also involves an over active immune system, which essentially attacks the protective sheath surrounding nerves.
Symptoms of multiple sclerosis include pain, loss of mobility, muscle spasms and changes in mood.
CBD seems to exert an immune modulatory effect and this, alongside being anti-inflammatory and neuroprotective, has provoked interest in its use in MS.
Studies do indicate that CBD may help with pain and muscle spasms (17).
A prescription oral spray containing CBD and THC is used in the treatment of MS related spasms.
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Mood and Anxiety
One of the many ways in which cannabinoids have been shown to work is by acting on mood influencing receptors such as the 5-HT1A receptor.
CBD has been shown to have antidepressant like effects in mice, this is thought to be down to activation of the 5-HT1A receptor (18).
A reduction in anxiety in rodent studies was also attributed to the action of CBD on the 5-HT1A receptor (19).
In human trials on anxiety in social phobia, pre-treatment with CBD prior to speaking at a public event significantly reduced anxiety and cognitive impairment (20).
Another study also found CBD to reduce symptoms of generalised social anxiety disorder (21).
The use of cannabis has been linked to the development of mental health problems including schizophrenia.
This is though to be down to the presence of the psychoactive compound THC.
CBD is known to have no psychoactive activities and may in fact have antipsychotic actions.
One study showed that using CBD was as effective as standard antipsychotic medication (22).
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Pain and Inflammation
Inflammatory conditions are on the rise and links are being made to conditions not previously thought to involve inflammation.
These include depression, obesity and Type 2 diabetes.
Inflammation is a natural immune response that has useful actions for repair following injury or infection.
But chronic low grade inflammation is known to cause damage in a variety of ways.
CBD may act in several ways to curb inflammation. It has been shown in several studies to improve inflammation in animal models of conditions such as Type 1 diabetes, rheumatoid arthritis, osteoarthritis, and inflammatory bowel disease (23).
This may be down to the fact that CBD has a strong ability to inhibit the production of inflammatory messengers, called cytokines (24).
Although human studies are still in their infancy compared to animal studies, a survey involving people taking CBD for pain issues like back pain, neck pain, fibromyalgia and migraine indicated significant improvements in pain scores which allowed pain medication to be adjusted (25).
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Cardiovascular Disease
In light of the emerging evidence on CBD actions and potential benefits, recent interest has turned to its possible role in cardiovascular health.
It is now known that many cardiovascular issues involve inflammation and in animal studies CBD has been found to have multiple actions that may impact cardiovascular functioning.
CBD is not only anti-inflammatory and has antioxidant properties but may also aid in blood vessel relaxation (26).
In a study involving healthy volunteers, CBD was shown to lower resting heart rate and prevent blood pressure form rising too high after experiencing a stressful event (27).
Rodent studies indicate that CBD may have a cardioprotective effect (28,29).
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Cancer
CBD has been used alongside THC for side effects associated with cancer treatments.
A prescription cannabinoid preparation is licensed for the reduction in nausea and vomiting associated with chemotherapy treatments.
Alongside reducing symptoms, CBD may also possess anti-cancer actions.
In vitro and animal studies indicate it may prevent the growth and spread of tumours (30).
Research conducted on breast, colon, lung and brain cancer cells shows promise (31).
Although these preliminary studies are showing positive results, clinical trials in humans will give a clearer picture of CBD in cancer.
Trials are currently being conducted into the use of cannabinoids in a particular type of brain cancer.
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Contraindications
Research shows that CBD may interfere with the breakdown of certain medications in the liver by inactivating certain enzymes – this may increase the levels of some medications in the blood (32).
As CBD has potentially blood pressure lowering effects, caution should be exercised in those who already have low blood pressure.
There are few side effects related to the use of CBD but at high doses some people have reported diarrhoea, dry mouth and tiredness (33).
This may not be a problem with lower doses. In fact, getting the right dose is vital as effects seem to drop off with too low or too high a dose (34).
The research behind CBD and health is still emerging and although in vitro and animal studies show some promising benefits, further clinical trials in humans are needed to ascertain the full mechanisms and benefits of using CBD.
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