BlogWhat is the difference between THC and CBD?

What is the difference between THC and CBD?

8 min read

Sam North

What is the difference between THC and CBD?

Next up in our new patient series, we are going to take a brief but in-depth look at how the cannabinoids that dominate the cannabis-based medicine scene, THC and CBD, differ from one another, and how they can also work in harmony to provide relief for a range of medical conditions.


The two dominant cannabinoids produced by cannabis plants are THC (tetrahydrocannabinol) and CBD (cannabidiol). To date, researchers have isolated more than one hundred different of these special compounds from cannabis, but only these two have been thoroughly researched.

From the different therapeutic effects to the legality and potential side effects, we will quickly cover all you need to know. By the end of today's write-up, you will be equipped with a deeper understanding of THC and CBD and how they may help you on your journey towards improved health.

THC: the psychoactive cannabinoid with therapeutic value

THC is the cannabinoid that made cannabis famous.

It's the psychoactive compound responsible for the characteristic 'high' associated with recreational marijuana use, and the main reason cannabis has just emerged from more than a century of demonisation, prohibition, and social stigma.

But there's more to THC than just being the plant's main psychoactive ingredient. It also has a bunch of potential therapeutic effects, making it valuable for medical applications.

What medical benefits does THC offer patients?

A few of the key therapeutic effects of THC include:

  • Pain relief - Chronic pain is the condition most commonly treated with cannabis-based medicines here in the UK, and THC has been found to be the primary cannabinoid responsible for the plant's pain-relieving effects.
  • Nausea and appetite stimulation - THC has been shown to help alleviate vomiting and nausea and boost appetite.
  • Muscle relaxation and spasticity - THC has been associated with reduced muscle stiffness and spasticity in patients with MS.
  • Mental health conditions - There is evidence to support the use of THC as a treatment for anxiety disorders, although dosage sizing is very important.
  • Inflammation - THC has shown anti-inflammatory properties and may help with conditions such as arthritis, Crohn's disease, and gastroenteritis.

Is THC legal in the UK?

Yes, but only when it has been prescribed by a specialist registered with the General Medical Council (GMC). Recreational marijuana use remains illegal in the UK.

CBD: the non-psychoactive cannabinoid gaining attention

The truly meteoric rise of CBD over the past decade or so should come as no surprise.

Not only has it been found to offer a multitude of potential therapeutic effects, but unlike THC, CBD is non-psychoactive. Taking medical-grade CBD products will not cause you to feel 'high' whatsoever, but they can have a calming influence on the mind and body.

What medical benefits does CBD bring to the table?

The current body of clinical research is ever-growing, but so far, researchers have found that CBD may bring relief from:

  • Epileptic seizures - CBD oil has been found to be the most effective phytocannabinoid for controlling and reducing the frequency of seizures in many different conditions, with a focus on rare, treatment-resistant forms of epilepsy.
  • Mental health issues - CBD's interactions with serotonin and GABA receptors in the brain may provide relief from anxiety and depression.
  • Inflammation - Like THC, CBD has anti-inflammatory properties and may help with chronic pain, arthritis, and other inflammatory conditions.
  • CBD's antioxidant properties may play a role in the neuroprotective effects of the cannabinoid and offer a potential treatment option for neurodegenerative diseases.

Is CBD legal in the UK?

Yes, but with a few caveats.

'Over-the-counter' CBD products are only legal if they have less than 1mg of THC per product/container.

These products may not be subject to as stringent oversight or regulation as medical-grade CBD products, so it's always best to consult with a specialist before taking them.

What are the potential side effects of THC and CBD?

Although the psychoactivity of THC can cause issues for some patients, both cannabinoids have been found to have a high safety profile with minimal side effects.

As with any treatment, though, there are potential side effects to be aware of.


  • Psychotropic effects - The most well-known side effect of THC is the feeling of being 'high' or euphoric. These effects can benefit some patients, but others may find them unpleasant.
  • Dry mouth and eyes - THC consumption has been associated with decreased saliva production and dry, red eyes.
  • Impaired memory and cognition - Some studies have found that chronic use of THC can lead to impaired short-term memory and cognitive function.
  • Increased heart rate - THC administration has been linked to an increased heart rate, which may be problematic for patients with pre-existing conditions.


  • Drowsiness or fatigue - CBD's calming effects may make some patients feel drowsy or fatigued after taking it.
  • Nausea or diarrhoea - CBD may cause these gastrointestinal side effects when administered in high doses.
  • Drug interactions - CBD can interact with certain medications, potentially affecting their effectiveness. Consult with a specialist before taking CBD if you are on any other medications.


What is medical cannabis?

In the simplest terms, medical cannabis relates to any products or medications derived from the cannabis sativa L. plant that are administered to treat medical conditions and alleviate symptoms.

When did medical cannabis become legal in the UK?

Cannabis-based therapy options became legal almost 6 years ago here in the UK, in November 2018.

Will the NHS cover my medical cannabis costs?

There are two routes for patients to seek a prescription.

Currently, the NHS will only provide cannabis prescriptions for three conditions - two rare types of severe epilepsy, vomiting or nausea caused by chemotherapy, and muscle stiffness caused by MS.

For all other conditions, new patients will need to work with a private medical cannabis clinic like Releaf.

What are cannabinoids?

There are three types of cannabinoids.

  • Endocannabinoids - Endogenous cannabinoids are naturally produced within the human body and interact with endocannabinoid receptors, regulating many bodily functions such as appetite, sleep, and mood.
  • Phytocannabinoids - These come from plants, such as cannabis, and interact with our body's endocannabinoid receptors, but slightly differently from the endocannabinoids.
  • Synthetic cannabinoids - Cannabinoids that are lab-created. Nabilone, an NHS-prescribed CBPM used to treat the nausea and vomiting caused by chemotherapy, contains a synthetic version of THC. 

Both endocannabinoids and phytocannabinoids bind with endocannabinoid system receptors throughout our brain and body to produce a range of therapeutic effects. 

THC and CBD: finding the right balance for your treatment

As with any medical treatment, finding the right balance for your unique health needs is essential. Thankfully, there is now a wide range of medical-grade THC and CBD products available, allowing specialists to really fine-tune dosages and tailor treatment plans.

If you think that cannabis-based medicines may be the right option for you, reach out at any time. We are committed to helping patients start out with this complementary, natural treatment option. Our team of patient support staff and specialists are here to answer any questions you may have and guide you towards the best possible treatment plan for your specific needs.

If you want to learn more, check out our blog and education section for more in-depth readi

It is important to seek medical advice before starting any new treatments. The patient advisors at Releaf are available to provide expert advice and support. Alternatively, click here to book a consultation with one of our specialist doctors.

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Sam North, a seasoned writer with over five years' experience and expertise in medicinal cannabis, brings clarity to complex concepts, focusing on education and informed use.

Our articles are written by experts and reviewed by medical professionals or compliance specialists. Adhering to stringent sourcing guidelines, we reference peer-reviewed studies and scholarly research. View our editorial policy.

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