What is THC (Tetrahydrocannabinol) and How Does it Work?

This article introduces you to THC (Tetrahydrocannabinol) and explains how this compound, found in the cannabis plant, can be used for medical purposes as well as providing some advice about dosing THC and how it interacts with CBD.

Table of contents
  1. What is THC?
  2. How Does THC Affect the Body?
  3. How is THC Processed or Metabolized By the Body?
  4. How Do CBD and THC Interact with Each Other?
  5. What Medical Benefits and Uses Does THC Have?
  6. How Much THC Should I Use?
  7. What Are the Risks of THC?
  8. How Do I Overcome THC’s Negative Effects?
  9. Are There Any Other Psychoactive Cannabinoids?
  10. What is Tetrahydrocannabinolic Acid (THCA)?
  11. Are There Legal Forms of THC Available by Prescription?
  12. Which Medical Marijuana Strains Are High in THC?
  13. Is THC a Good Choice for You?
  14. THC Key Takeaways
Download Free Guide to THC

THC is the main psychoactive compound found in the cannabis plant, and directly attaches itself to receptors (CB1 receptors) in the brain. THC is often the cannabinoid found in the highest concentrations in the cannabis plant. Many people demonize THC, thinking it is the “non-medical” part of cannabis, but it actually works in tandem with CBD for enhanced therapeutic effects. Our bodies could be said to produce its own natural THC, called anandamide. Alongside endorphines, serotonin and dopamine, anandamide plays a role in enjoyment, pleasure and bliss. When we have a shortage of this natural THC, using THC derived from cannabis plants could be used as a replacement.

THC could be very useful for the treatment of chronic pain, autoimmune disorders, cancer, nausea, multiple sclerosis, Parkinson’s Disease, Alzheimer’s Disease, and insomnia. Another interesting thing about THC is that, if we weren’t trying to figure out how it works, we wouldn’t have discovered the endocannabinoid system (ECS).

If there are any scientific terms you do not understand, check out our glossary.

What Is THC?

THC stands for tetrahydrocannabinol, which is one of 150 cannabinoids found in the cannabis plant. A cannabinoid is a class of compounds that interact with the body’s own natural endocannabinoid system (ECS).

Other names for tetrahydrocannabinol include trans-delta9-THC, or delta-9-THC. The chemical formula for THC is C21H30O2. THC is the main psychoactive component of the cannabis plant, and is a partial agonist of both the CB1 and CB2 receptors. This means that THC can partially turn on CB1 receptors in the brain (hence the psychoactivity) and the CB2 receptors in the immune system (hence the anti-inflammatory effects). This makes THC an effective painkiller, and could also be useful as an anti-inflammatory, spasticity, antiemetic (nausea/vomiting prevention), appetite stimulant, and a treatment for an overactive bladder.

Chemical formula for THC, tetrahydrocannabinol. C21H3002
THC chemical formula, C21H30O2. Source. Author: Erzebethh, Pixabay.com.

How Does THC Affect the Body?

The effects of THC include elation, anxiety, tachycardia, short-term memory recall issues, sedation, relaxation, and pain-relief. The psychoactive effects of THC are thought to be due to the activation of CB1 receptors and inhibition of the enzyme fatty acid amide hydrolase (FAAH), which increases the amount of anandamide available in the body.

THC also stimulates cells in the brain to release dopamine. Dopamine is seen as the main hormone associated with pleasure, but this is not entirely accurate. Rather, dopamine plays a role in motivation and reward-seeking behavior, as opposed to pleasure directly. This combination affects a person’s memory, pleasure, movements, thinking, concentration, coordination, and sensory and time perception.

Using THC results in the decrease of the concentration messenger, cAMP (cyclic adenosine monophosphate). cAMP is associated with several important biochemical processes, including the regulation of glycogen, sugar, helping hormones pass through plasma membrane, and lipid metabolism.

The indirect effect of THC on dopaminergic neuron.
The indirect effect of THC on dopaminergic neurons. Cannabinoid receptor activation reduced calcium ion influx, reducing vesicle fusion, reducing GABA release. Reduced GABA in synapse decreases the influx of chloride ions into the dopaminergic neuron. This reduced inhibition increases dopaminergic excitability, hence increased dopamine release. Author: Mariska Twaalfhoven. Source

How is THC Processed or Metabolized By the Body?

THC is metabolized mainly to the metabolites 11-Hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) and 11-Nor-9-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC or THC-COOH) in the liver. 11-OH-THC is particularly psychoactive, and edibles are more readily metabolized into this metabolite compared to vaping cannabis. Basically, eating cannabis is stronger than vaping it or using a tincture, as it passes through the liver and turns into a more potent version of THC.

Metabolism occurs mainly in the liver by cytochrome P450 enzymes CYP2C9, CYP2C19, CYP2D6, and CYP3A4.

How Do CBD and THC Interact with Each Other?

We recommend reading our page on how CBD works. The interaction between THC and CBD is complex, but here’s a general guide, which is based upon mostly anecdotal reports:

  • All THC, no CBD = short-lived but intense psychoactive effect.
  • Lots of THC, some CBD = longer-lived but less intense psychoactive effect.
  • Equal amounts of THC and CBD = few psychoactive effects. There may be some, but they are likely to be more gentle.
  • High amounts of CBD, little or no THC = no psychoactive effects.

CBD is actually a CB1 antagonist, but with a weak affinity for the CB1 receptor, meaning it doesn’t bind to it very strongly. This means it can block or buffer THC’s effects to some extent, depending on dosage and ratio. A 1:1 CBD:THC ratio effectively reduces THC’s psychoactive effects. More CBD than THC, and THC’s psychoactivity is reduced to a minimum, if felt at all. Other terpenes and cannabinoids also impart their effects, so it is best not to forget about these.

ALT Text: THC chemical formula. C21H30O2. Chemical structure of CBD, C21H30O2.
Atakan, Zerrin. (2012). Cannabis, a complex plant: different compounds and different effects on individuals. Therapeutic advances in psychopharmacology.

What Medical Benefits and Uses Does THC Have?

When dosed appropriately, THC has multiple medical benefits, and can be used for:

THC can be used to help reduce or eliminate pain, increase the amount of time and quality of sleep, increase appetite, and decrease muscle spasticity and tremors. In older people, small amounts of THC can be used to potentially improve memory and promote neurogenesis.

THC may be generally more useful for adults aged 25 or over, except in certain medical cases. This is because THC can negatively impact the developing brain. We recommend consulting a doctor before giving THC to a minor, or if you are under the age of 25.

Schematic showing high-level multi-step process of neurogenesis and gliogenesis.
Schematic showing high-level multi-step process of neurogenesis and gliogenesis. Neural stem cells have the potential to generate all neural cell types, such as neuron (neuronal progenitor), astrocytes and oligodendrocytes (glial progenitors). Author: Audrey Effenberger. Source | CC BY-SA 4.0

How Much THC Should I Use?

You needn’t use psychoactive amounts of THC to take advantage of its benefits. The usual recommendation is around 2.5 mg of THC once or twice a day, only increasing if you feel the THC isn’t helping you. In more severe cases of chemotherapy-induced nausea, 5 mg of THC three to four times a day may be recommended.

These are the sorts of dosage guidelines for the use of dronabinol, which is a synthetic form of THC that is sometimes prescribed to cancer or AIDS/HIV patients, and occasionally those who suffer from chronic pain or multiple sclerosis. Those who find such doses overwhelming may use CBD to balance out these effects. The trade name for dronabinol is Marinol or Syndros.

What Are the Risks of THC?

You should not use THC at all if you suffer from schizophrenia, a schizotypal disorder or any mental health problem that could cause mania, extreme delusions or hallucinations. CBD may be more useful for such mental health problems due to its antipsychotic effects.

While THC generally decreases pain, it can also increase sensitivity to pain in some people. There could be several reasons why, including individual differences in individual’s endocannabinoid systems (ECS). Using too much THC can cause drowsiness, cotton-mouth, euphoria, and tachycardia. Higher amounts can result in lethargy, slurred speech, decreased motor coordination, anxiety/paranoia, and postural hypotension.

As for other drugs THC that are contraindicated by THC, there are some. THC interferes with the metabolization and/or increases the effects (acts synergistically) of opioids, benzodiazepines, sedatives and anti-rejection medication for organs. Caffeine may act synergistically with THC. Some say myrcene can also increase THC’s sleepy effects. Myrcene can be found in hops and mangoes.

Download Free Guide to THC

How Do I Overcome THC’s Negative Effects?

There are several strategies to overcome a negative cannabis experience. Overall, we recommend the following.

  1. Relax – drink some water, put your feet up, listen to some relaxing music, and remember that it will all be over soon.
  2. Use cannabidiol (CBD) in equal ratios to THC (e.g. if using 2.5 mg THC, use 2.5 mg CBD). This can help buffer THC’s negative effects.
  3. Expose yourself to pinene. Pinene is found in pretty much every cannabis strain, and can also be used to counteract some of THC’s negative effects. Pinene has a “refreshing” effect on many people. Taking a walk through some woods or green spaces can be helpful. Pine trees, spruce trees, chamomile, saffron, parsley, rosemary, sage, mint and oregano all contain pinene.
  4. Chew on black peppercorns. Chewing on a few black peppercorns may help alleviate some of the anxiety associated with overconsumption of THC.
  5. Follow a hot showers with capsaicin cream. THC and CBD can desensitize the receptor, TRPV1, which is responsible for heat detection. Hot showers and capsaicin cream can reawaken TRPV1 receptors, and the negative effects of THC will subside.

Are There Any Other Psychoactive Cannabinoids?

Yes. Other psychoactive cannabinoids include:

  • Cannabinol (CBN) – mildly psychoactive. THC breaks down into CBN as it ages. CBN may be particularly useful for insomnia.
  • Tetrahydrocannabivarin (THCV) – a CB1 receptor antagonist in lower doses, and a CB1 receptor agonist in higher doses. This means that THCV can both decrease and potentiate THC’s psychoactive effects, depending on dosage. THCV has biphasic effects.
  • Tetrahydrocannabiphorol (THCP) – a particularly potent and psychoactive cannabinoid that has a high affinity for CB1 receptors. THCP could be 30 times more potent than THC, but is not usually found in high concentrations.
  • Tetrahydrocannabutol (THCB) – shows an affinity for both CB1 and CB2 receptors, and may be a partial agonist of the CB1 receptor. Has a greater affinity for CB1 receptors than THC, so is also potentially more psychoactive than THC.
  • Delta-8-THC – Differs from delta-9-THC by only a few atomic bonds, but has a lower affinity for CB1 receptors. This makes delta-8-THC psychoactive, but not to as great an extent as delta-9-THC.

It is possible to utilize the above cannabinoids in combination with THC in order to create a greater psychoactive effect. In fact, using the above in such a manner can reduce the amount of THC needed for psychoactive effects! Similarly, you can also use terpenes and cannabinoids to reduce THC’s psychoactive effects. Check out our cannabinoid and terpenoid table if you’d like to know more.

CBD also produces a physiological effect, so could be seen to be psychoactive, even if it’s not psychoactivity in the traditional sense. CBD also buffers or “blocks” THC when used in equal or greater amounts.

What is Tetrahydrocannabinolic Acid (THCA)?

Some of our clients have asked about THCA, which is what THC is before it becomes THC. There is some debate as to whether or not THCA has any therapeutic value, but some have claimed that there is.

THCA is the non-psychoactive, non-decarboxylated, acidic precursor to THC. THCA is found in raw and live cannabis, and is converted into THC as the cannabis ages or is heated up. When the carbon group of THCA is removed by heat (i.e. smoking or vaping), it is converted into THC and produces psychoactive effects.

THCA’s chemical formula is C22H30O4. THCA may also have anti-inflammatory properties. Many use THCA as an alternative to THC in order to reduce psychoactive effects whilst also retaining some of its inflammation-beating properties. THCA may be particularly useful for children because of this.

Chemical structure of THCA - Tetrahydrocannabinolic Acid. Removing CO2 converts THCA to THC.
Chemical structure of THCA. Removal of CO2 turns THCA into THC. Author: Cacycle. Source

Yes. THC is available in synthetic form in the United States, going by the name dronabinol (trade name Marinol or Syndros). It is usually prescribed for cancer patients, AID/HIV patients or those undergoing chemotherapy. Dronabinol is a Schedule III substance, despite being more psychoactive and less tolerable than THC. Another form of synthetic THC is also available on prescription, called nabilone (brand name Cesamet).

Which Medical Marijuana Strains Are High in THC?

There are many types of cannabis that contain high amounts of THC. White Widow, White Rhino (aka Medicine Man), Bruce Banner, Jack Herer, Sour Diesel, Girl Scout Cookies, Chemdawg and Gelato are examples of cannabis varieties that contain high amounts of THC. The best way to know what varieties have high concentrations is to ask the budtender at the dispensary which strains have tested highest for THC.

Cannabis strain Jack Herer, a variety known for high amounts of THC. Generic term is Bedrocan.
Jack Herer cannabis strain. Source.

Is THC a Good Choice For You?

THC has been unfairly demonized, with many now believing that only CBD is “medical” part of the cannabis plant. Yet, THC has a number of potential medical uses, and can even help make CBD more effective via the entourage effect. Therefore, it is best to remain open-minded towards THC, and use it in small doses (and on some occasions higher doses) in order to get benefits from it.

Remember – THC Key Takeaways:

  • THC is the main psychoactive cannabinoid found in cannabis, as it is a partial agonist of CB1 receptors in the brain.
  • CBD and pinene may be used to balance out THC’s psychoactive effects.
  • THC is not the non-medical part of cannabis. THC has multiple medical uses, including as a painkiller/distractor, antiemetic, appetite stimulant, neuroprotective antioxidant, and a way to treat spasticity and tremors.
  • Low doses of THC may be useful for treating a number of conditions. You do not have to get “stoned” or “high” to get THC’s benefits. Anxiety, insomnia, nausea and chronic pain may be successfully treated with the use of THC and a mixture of other cannabinoids and terpenes.

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Written by
Dipak Hemraj
Dipak Hemraj

Dipak Hemraj is a published author, grower, product maker, and Leafwell’s resident cannabis expert. From botany & horticulture to culture & economics, he wishes to help educate the public on why cannabis is medicine (or a “pharmacy in a plant”) and how it can be used to treat a plethora of health problems. Dipak wants to unlock the power of the plant, and see if there are specific cannabinoid-terpene-flavonoid profiles suitable for different conditions.

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