What is Tetrahydrocannabinol (THC)?

Alternaleaf Team
Written by
Alternaleaf Team
Apr 14, 2023
Last updated:
May 2, 2024

Tetrahydrocannabinol (THC) is a key active ingredient in medical cannabis. One of the more than 100 cannabinoids found in the cannabis plant, THC is perhaps the most well-known and the one responsible for cannabis' more infamous psychotropic effects.

Read on for the lowdown on THC and how it’s used in medicine.

What Is THC?

The cannabis plant contains dozens of chemically active compounds called cannabinoids. Each of these cannabinoids interacts with receptors throughout our body, including our brain, nervous system and immune system.

THC may be the best known cannabinoid and it was the first to be discovered in 1964. Famous for its euphoric and psychoactive properties, it's responsible for the signature “high” associated with cannabis use.

It’s also one of the most common cannabinoids. Along with CBD, THC makes up the majority of active cannabinoids in most strains of cannabis. Other cannabinoids like CBN and CBG occur in much smaller quantities.

How Does THC Work?

THC affects our bodies by binding to receptors in our endocannabinoid system (ECS). These receptors are designed to recognise endocannabinoids, which are chemicals that occur naturally in our body and have similar structures to cannabinoids.

When we consume THC, it bonds to specific receptors called CB1 receptors. These exist primarily in our brain and nervous system but also other organs such as the gastrointestinal system.

One of the most well-known effects of THC is a feeling of euphoria, commonly referred to as a "high." THC can also cause an increase in appetite, commonly known as "the munchies," as well as a decrease in anxiety and pain. However, THC can also have some negative side effects, such as impaired coordination and memory, along with paranoia and anxiety.

It's important to note that the effects of THC can vary depending on the individual and the method of consumption. Smoking or vaping cannabis can result in a quicker onset of effects, whereas consuming edibles can result in a delayed onset and stronger, longer-lasting effects.

What's the Difference Between THC and CBD?

THC and CBD occur together in the cannabis plant in varying quantities. Some strains may have lots of THC and minimal CBD, or vice versa, while others will have an equal amount of both.

The ratios of THC to CBD matter because each cannabinoid affects our bodies and brains differently. While THC is a psychoactive compound affecting our mind and perception, CBD has a more subtle effect on the body. CBD is not psychotropic and doesn't cause a "high". However, it still has medicinal effects and is often prescribed for pain, inflammation, and anxiety.

Understanding the difference between THC and CBD is helpful when understanding your prescription and the different options available. Depending on your condition, symptoms, and lifestyle, you may benefit from a different combination of THC and CBD.

What Is THC Prescribed for?

In Australia, doctors can prescribe medical cannabis for any condition if it benefits the patient. There is no restricted list of qualifying conditions that are approved for treatment with cannabis, which is the case in other countries. The only requirement is that patients must have a chronic condition that has lasted for longer than 3 months and that has proven resistant to traditional treatment methods.

Patients will work with a doctor to discuss their current health concerns, medical history and past treatment options. Then the doctor will determine the best course of action, including a possible prescription for THC-containing medical cannabis.

Medical cannabis products in Australia are categorised based on their THC and CBD content. Most common medical cannabis products contain a combination of THC, CBD and  other cannabinoids.

Working with a doctor to determine the right product, dose, and strain for your condition and needs is essential. For example, a high-THC product may work well for chronic pain in one patient but not another. Equally, a high-CBD product may be more suitable in some circumstances, depending on the patient and their symptoms.

Medical Benefits of THC

Research suggests that THC could be a promising treatment for a wide variety of conditions. In studies, THC has been used to alleviate symptoms of conditions such as chronic pain, multiple sclerosis and chemotherapy-induced nausea and vomiting.

THC has also been found to have potential in treating mental health conditions, such as post-traumatic stress disorder (PTSD) and anxiety (although this is more notable at low levels; higher THC doses can exacerbate anxiety symptoms). However, more research is needed to fully understand the potential benefits and risks of using THC for mental health conditions.

Is THC Safe?

Medicinal cannabis containing THC is considered a “relatively safe drug,” by the TGA, the Australian Journal of General Practice and other trusted organisations. Overconsumption of THC-rich cannabis is rare, with the most common adverse side effects being dizziness, anxiety and a racing heart.

THC is classified as a Schedule 8 medicine in Australia and can be prescribed by doctors under the TGA Special Access Scheme. This means that while medicinal cannabis hasn’t been approved for general use, doctors can request access to prescribe it if they believe a patient will benefit and other treatments have been tried.

However, there are some circumstances where THC is not recommended. In particular, it’s not recommended that children or teenagers use THC. Additionally, if a patient has a family history of psychosis, THC could make them more vulnerable to experiencing psychosis or schizophrenia.

How Much THC is There In Cannabis?

The concentration of THC in cannabis can vary widely depending on the strain, growing conditions and method of cultivation. In general, THC concentrations are highest in the  buds of the female cannabis plant, which is where the majority of medical cannabis flower comes from.

Traditionally, cannabis with a THC concentration of 0.3% or higher was considered to be marijuana, while cannabis with a lower THC concentration was considered to be hemp. However, these definitions have become more nuanced as the use of cannabis has become more widespread.

Typically, medical cannabis flower will have a THC concentration between 18% and 30%, although most strains are between 22-25%. Your doctor will prescribe a THC level suitable for your level of experience and comfort. Strains with more than 25% THC are generally not advised for inexperienced cannabis users.

It's important for patients to be aware of the concentration of THC in the products they are using, as higher concentrations can result in stronger effects and increased risk of negative side effects. Additionally, some individuals may be more sensitive to THC than others, so if you're new to medical cannabis you should always follow the maxim of "start low and go slow".

Is THC Right For You?

THC is one of the main active compounds in medical cannabis and is responsible for many of its psychoactive and therapeutic effects – along with its potential, less pleasant side-effects. But how THC might affect you will depend on the dose, method of delivery and your genetics, experience and  condition.

To find out if THC could benefit your chronic condition, book a consultation with a doctor at a medical cannabis clinic or your local GP. They'll be able to support you in finding the right treatment for your chronic condition.

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