As the laws and processes for prescribing and dispensing medicinal cannabis in Australia continue to improve, more patients are asking ‘what is the difference between CBD and THC’?

CBD and THC are both cannabinoids derived from the cannabis plant, however, they are different in many ways – from how they interact with the endocannabinoid system, the side effects they may cause and the laws and legalities that differ between them. Let’s take a closer look at their differences below.

Please note: CDA Clinics does not endorse the use of medicinal cannabis without lawful prescription. Just like any medicine, medicinal cannabis may have both positive and negative side effects on the user and should only be prescribed to patients by a health professional with the authority and expertise to do so. Patients considering medical cannabis are advised to speak to their doctor or a CDA clinician first to see if it’s a suitable therapy. 

Cannabinoid Effects

The most significant difference between THC and CBD is their effects and how they interact with the endocannabinoid system in the human body.

Tetrahydrocannabinol (THC) is a psychoactive cannabinoid that is responsible for the main intoxicating effects cannabis produces. THC is a powerful cannabinoid that interacts with your endocannabinoid system by binding to and interacting with the CB1 and CB2 receptors in the human body.

The CB1 receptors are primarily found in the brain and central nervous system. The CB1 receptors can also be found in lower densities in the peripheral nervous system, as well as the reproductive, adipose and connective tissues.  Depending on their location, CB1 receptors moderate:

  • Memory
  • Mood
  • Motor function
  • Sleep
  • Perception of pain

CBD, also known as cannabidiol, is a non-psychoactive cannabinoid that does not produce intoxicating effects. CBD targets the CB2 receptors, which are found primarily in cells of the immune, reproductive, respiratory and cardiovascular systems. CB2 receptors influence most physiological processes including:

  • Immune function
  • Inflammation
  • Digestion
  • Blood sugar levels
  • Weight management
  • Neuroprotection
  • Nociception
  • Synaptic plasticity

Side effects of THC and CBD

All medicines bring with them potential side effects. The Therapeutic Goods Administration Australia (TGA) states that the known side effects of medical cannabis treatment for both CBD and THC products include:

  • Decreased or increased appetite
  • Dry mouth
  • Diarrhoea
  • Fatigue and sedation
  • Vertigo
  • Nausea and vomiting
  • Fever

One of the key side effects that THC may cause that CBD does not is coordination problems and red eyes. This is primarily due to the psychoactive component that THC contains that CBD does not. To minimise side effects from these medicines, it is important that eligible patients use a titration dosing method.

The Legality of THC and CBD

Another key difference between CBD and THC is their legalities.

In Australia, CBD is classified as a schedule 4 drug and THC is classified as a schedule 8 drug. The drug schedule is dependent on the CBD and THC cannabinoid content in the medicine:

  • A cannabis medicine is schedule 4 when the total THC content is below 2%.
  • A cannabis medicine is schedule 8 when the total THC content exceeds 2%.

The TGA defines a schedule 4 medicine as a prescription only medication and defines a schedule 8 medicine as a controlled drug.

Australian patients taking medical cannabis must be aware that it is illegal to drive with any THC in their system. This is due to the psychoactive component in THC that CBD does not contain. It is vital to discuss with your doctor whether your product may contain any THC.

While CBD alone doesn’t commonly cause any impairment, please always check your state legislations and consult with your doctor to see whether you can drive on the specific cannabis medicine you have been prescribed.

It’s also important to understand that having a medical cannabis script or TGA approval documentation is not a valid defiance against prosecution under Australian laws.

Choosing between CBD or THC

With such key differences between these two cannabinoids – from the laws surrounding them, the potential side effects that they can cause and the receptors they bind to within your body – deciding which cannabinoid is right for you should be left up to a health professional that is trained in medicinal cannabis therapies.

If you are interested in plant-based alternatives as a treatment option, please speak to your doctor or a medical cannabis clinician.