CBD:THC ratio explained

The use of cannabis for medicinal purposes is becoming more and more accepted throughout many countries. With the increased use of these medicines, the CBD:THC ratio is becoming more important. As popularity grows, research is being done to further understand the therapeutic benefits of different combination formulations and doses.

Currently, in New Zealand, only one medicinal cannabis product (Sativex) has been approved by Medsafe. This is for use as an add-on treatment for the symptoms of moderate to severe spasticity due to multiple sclerosis (MS). Sativex contains equal amounts of CBD and THC (a 1:1 ratio).

However, a broader range of CBD:THC combinations are being investigated to treat other indications, such as pain, epilepsy, anxiety, sleep disorders, etc. These combinations range from CBD-dominant to THC-dominant, for example, CBD:THC 20:1 through to CBD:THC 1:10.

Understanding which combination to use on individual patients is challenging. The following sections provide guidance to help understand how the ratio of CBD:THC works so that going forward you can improve the effectiveness of medicinal cannabis.

Understanding CBD and THC

Cannabidiol (CBD) and tetrahydrocannabinol (THC) are both natural compounds found in plants of the Cannabis genus. Although both compounds interact with the body’s endocannabinoid system, the effects of these two compounds are very different. THC binds to CB1 receptors in the brain and causes feelings of euphoria or ‘a high’. CBD binds weakly to the CB1 receptor and only when THC is present. CBD does not produce euphoria or ‘a high’.

CBD and THC can be combined in medicinal products in different ratios to produce different therapeutic effects. Because the use of medical cannabis is a relatively new area in medicine, there is still a lot of research to be done in this area. We are still learning what ratios are best for managing various conditions.

What is a CBD:THC ratio?

The ratio of CBD to THC indicates the amount of CBD compared to the amount of THC in a dose. For example, a ratio of 1:1 would mean that the amount of CBD and THC are the same in each dose. A CBD:THC ratio of 20:1 would mean that there is 20 times the amount of CBD in a dose compared to THC. Changing the ratio of CBD to THC allows for a tailor-made product that utilises the unique effects of either CBD, THC, or both for a particular patient or clinical effect.

What are the most common ratios?

Cannabis cultivars grown for the recreational market have seen a steady increase in THC content, paired with a decrease in CBD. Smoking these varieties will give the user a more potent ‘high’, but this might come at the cost of some therapeutic effects.

Medical use of CBD and THC has changed that, allowing specific ratios of CBD:THC to be selected to provide the greatest clinical benefit for each patient. Now, most medicinal cannabis products are higher in CBD than THC. Pure CBD products are considered to have less than 0.3% THC. The trend has moved towards cultivating plants or producing products that have a higher CBD to THC ratio. Ratios of CBD:THC can range between >20:1 all the way to 1:10. As a general rule of thumb, anything higher than a CBD:THC ratio of 10:1 should not elicit a high.

CBD:THC ratio for pain

By changing the ratio of CBD to THC, you are able to target and manage different types of pain.

Mild to moderate pain due to inflammation (think arthritis-type pain) can be managed well with CBD-dominant products such as CBD:THC 20:1 and 10:1. These ratios will be unlikely to induce any intoxicating effects.

Neuropathic pain, from disease or damage to the nervous system, might be better treated by increasing the ratio of THC towards a balanced ratio, 1:1. The exact ratio will depend on the severity of the condition and how well THC can be tolerated by the patient.

Very severe pain, such as cancer pain, may require THC-dominant medications. It is important to understand that THC-dominant products may induce euphoria and sedation, so care needs to be taken.

CBD:THC ratio for anxiety

Smoking cannabis can induce paranoia or extreme anxiety in certain people, so it seems counterintuitive that you could use medical cannabis preparations for the management of anxiety.

CBD has demonstrated efficacy in treating various forms of anxiety and is commonly used for this purpose. However, recreational use of high-THC cannabis is associated with increased anxiety, particularly in high doses. Reports suggest that THC has a dose-dependent effect on anxiety, where at low doses THC may be anxiolytic (reduce anxiety) but at higher doses can be anxiogenic (cause anxiety). Therefore, CBD-dominant products (CBD:THC >10:1) are likely to provide the most beneficial treatment, and in some cases, pure CBD with no THC present may be the best product to treat anxiety.

CBD:THC ratio for insomnia

Insomnia is a widespread problem and has been linked to illnesses ranging from depression to cardiovascular disease to dementia. Many allopathic medications used in the management of insomnia have adverse side effects, such as daytime drowsiness or addiction.

THC is well-known to have sedating properties via its action at the CB1 receptor; however, its use alone can cause increased anxiety and lead to other undesirable effects. By adjusting the ratio of CBD:THC, it is possible to block these undesirable effects while still retaining sedating properties. A current study is looking at a CBD:THC ratio of 20:1 in the treatment of chronic insomnia. If you are taking medicinal cannabis for other indications, it may be possible to investigate adding a slightly higher dose of THC at night-time to maximise the sedating effects and reverting to the lower THC ratio for daytime use.

How to pick the best CBD:THC ratio for your patient

At the time this blog was published (January 2021), the only available medical cannabis in New Zealand contains a ratio of CBD:THC at 1:1; however, going forward you will be able to prescribe your patient other preparations of CBD:THC at a ratio that is optimal for what they want to achieve. The following is a rough guide of what to expect from different ratios:

CBD:THC at a ratio of 1:2

This preparation contains twice as much THC as CBD and will have intoxicating effects, especially for new or naive users. The presence of some CBD in the preparation will dampen some side effects of the higher THC, such as paranoia, but not all. This ratio would be better suited for people who have been using medical cannabis on a chronic basis, e.g., for intractable nausea, poor appetite, or glaucoma, and have developed a high degree of tolerance.

CBD:THC at a ratio of 1:1

This preparation contains equal amounts of CBD and THC and, depending on the dose, is likely to cause symptoms of euphoria or intoxication, especially in people who are naive to cannabis use. If using this ratio, it would be prudent to start with low doses and increase slowly according to tolerance.

CBD:THC at a ratio of between 2:1 and 4:1

Preparations with this ratio of CBD to THC can be psychoactive, especially to people who have poor tolerance for THC. The increased CBD does have beneficial effects and causes some dampening of the effects of THC.

CBD:THC at a ratio of more than 10:1

CBD:THC ratios >10:1 generally produce no intoxicating effects and are ideal for patients that are not able to take THC during the day (e.g., due to driving or work). Where the condition to be treated does not require THC, these products may help provide relief for certain conditions without any intoxication of the patient. This is a really safe dose for those people who want to experience the beneficial effects of CBD without the psychoactive effects of THC.

The bottom line

There is definitely an advantage to being able to adjust the ratio of CBD:THC in your medical cannabis preparation. This will allow you to maximise the particular benefits that you want while minimising any unwanted negative side effects. Currently, the standard preparation contains a fixed ratio of CBD:THC; however, going forward new research may strengthen the argument for flexible dosing.

THC is psychoactive and may impair your ability to undertake certain tasks, such as driving or operating machinery. CBD is non-psychoactive and non-sedating and can be safely used at much higher doses than THC.

With all medicinal cannabis, it is important to start with a low dose and gradually increase it over a few days. This is particularly important for compositions containing THC. Remember: START LOW and GO SLOW.

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