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What Is THC? A Scientific Look into Tetrahydrocannabinol


Delta-9 tetrahydrocannabinol is indisputably the most well known component of the cannabis plant, and those three letters—THC—are almost as recognizable as the iconic marijuana leaf.

Many people only know tetrahydrocannabinol as the main cause of marijuana intoxication and see it as simply a tool for getting high, but the full story of this compound is a lot more complex.

What is THC?

Tetrahydrocannabinol (THC) is the most abundant cannabinoid (an active chemical compound unique to cannabis) found in the cannabis plant. Most of the plant’s THC is located in trichomes, which are resinous glands located on the flowers of fully grown female plants.

THC trichomes

The way THC and most of the other cannabinoids (there are around 100 other cannabinoids currently identified) produce effects in humans is by interacting with the endocannabinoid system, an intricate network of cellular receptors (and activators) in charge of maintaining health and balance in the body.

You might be wondering why does the cannabis plant need THC in the first place?

Well, THC is not needed for growth, reproduction, or general development of the cannabis plant. Its function is most likely to protect the plant from outside attacks, acting like a vigorous immune system against herbivores, pests, viruses, bacteria and parasites.

Its other function is that it decreases the effects of the sun’s harmful UV radiation, because it absorbs UV-B rays. The majority of THC is located on the trichome glands of the flowers, which are found on the exposed outer surface of the flowers.

This mechanism ensures the survival of the plant, but humans have a neat way of discovering nature and so we soon realized that this compound also produces intoxication and sedation.

Tetrahydrocannabinol (THC) is a chemical compound found only in the cannabis plant. It serves as a defense mechanism, protecting the plant from various predators, bacteria, parasites and also the radiation of the sun.

The discovery of THC

Cannabis was greatly under-investigated before one man came along.

This figure, dubbed as the “Godfather of THC”, is Raphael Mechoulam, now a well-established and famed Israeli organic chemist.

At the start of the 1960s, Raphael was working as a researcher at the Weizmann Institute of Science in Rehovot, Israel. Mechoulam had a deep-rooted fascination with cannabis, and was astonished that there weren’t any serious studies being done on this amazing plant.

He decided to take matters into his own hands, and through a connection with the Weizmann Institute’s director he was able to acquire 5 kilograms of impounded Lebanese hash from Tel Aviv’s police department.

Mechoulam has said in his interviews that this was an under-the-table, unofficial type of deal, so he felt pretty nervous transporting such a massive quantity of hash on the bus ride from Tel Aviv back to Rehovot.

Raphael Mechoulam

After getting the required material for his research, Dr. Mechoulam and his team first successfully isolated an important cannabinoid, the non-intoxicating CBD (cannabidiol), in 1963.

One year later, tetrahydrocannabinol was discovered. The researchers mapped its structure and were able to synthesize THC.

After these breakthroughs,  Dr. Mechoulam no longer needed to use the services of the illegal market to get the hash required for his work. The Israeli Ministry of Health began supplying his team with all the material they needed.

Dr. Mechoulam also discovered the endocannabinoid system (ECS) in humans.

ECS has a role in regulating pain, memory, mood, and a number of other processes in humans. It consist of cellular activators (anandamide and 2AG) and receptors (CB1 and CB2).

Endocannabinoids are moleculary similar to cannabinoids found in cannabis, however they are produced naturally within our bodies.

An important endocannabinoid is anandamide.

It plays a role in regulation appetite, motivation, pain and pleasure and it is currently of interest to researchers due to its role in the extinction of unnecessary memories. Anandamide lasts for a short period of time which is measured in minutes (unlike THC which can affect us for several days).

One of the most important functions of the endocannabinoid system is to maintain homeostasis, the stable balance of functioning within the body.

Our endocannabinoid system is also activated when we consume cannabis.

Dr. Mechoulam has stated that he has never tried cannabis, refusing to compromise the validity and integrity of his research.

“I have never used it,” he said. “As I did research and we had an official supply of cannabis, obviously if we had used it for non-scientific reasons if people had come to know about it that would have stopped our work. Basically, neither I nor my students were interested.”

Tetrahydrocannabinol was discovered in 1964 by the Israeli organic chemist Dr. Raphael Mechoulam. The famed chemist also made several other important contributions to the science of cannabis, such as the discovery of the endocannabinoid system, and the isolation of CBD.

How THC affects the brain and the body

Parts of the ECS that are in charge of reacting to stimuli are called cannabinoid receptors, and THC has a strong binding affinity for them. Simply put, it attaches to CB1 and CB2 receptors.

Once enriched with THC, they “inform” other parts of the ECS to perform various chemical processes inside our body.

Cell sites that react to THC are located in three sections of our brain:

  • The hippocampus—located in the temporal lobe of the brain and responsible for memory formation. The effects of THC on the hippocampus can affect short term memory.
  •  The frontal cortex—where our thought processes occur and cannabinoid receptors in this part of the brain can regulate our thought patterns. THC causes the firing of neurons to be quicker than usual, which results in a more flowing train of thought that is closely linked with creativity.
  •  The cerebellum—in charge of movement and general coordination which is why we tend to feel slightly clumsy and uncoordinated when high.

The increased release of dopamine is another crucial factor for THC intoxication, and this chemical is a part of the primal reward system for desirable behaviors like reproduction and eating. Dopamine levels spike when the surge of THC reaches the brain, causing us to feel joyous, content, and euphoric.

Because of each individual’s unique personal chemistry, these effects can be happen in a lesser or greater amount.

While the majority of ECS cells are located in the brain and in the central nervous system, these cells are also found in many other parts of the body, including our reproductive organs, skin, and digestive tract.

Once THC reaches these cell receptors of the ECS, it causes a chain reaction that makes various parts of our body perform differently than usual, and as we know, also makes us feel quite different than we normally do.

While people usually need some time to get used to the cognitive and behavioral changes that THC creates (because they can be quite overwhelming at first), a whole series of reactions unnoticeable by our mind also happen at the same time.

Tetrahydrocannabinol engages the receptors of our endocannabinoid system, which when activated trigger a wide range of different chemical processes within the body.

Health benefits of THC

Because the THC-caused effects are profoundly diverse, we’re going to separate them into three stand-alone categories, where we’ll elaborate in great detail the short-term, medicinal, and long-term effects of tetrahydrocannabinol.

Before we start I should mention just a few general positive effects of THC, which include:

  • Better mood
  • Pain relief
  • Relaxation
  • Stress relief
  • Increased sociability

Short-term effects of THC

These are all immediate effects that happen after we ingest THC.

When we consume THC through smoke or vapor (with vaping, smoking, dabbing etc), effects happen within minutes.

With oral consumption (like capsules, oils and edibles), the initial effects start happening after about 30-60 minutes. The duration of the effects is also prolonged, lasting much longer than smoking or vaping.

A person’s unique individual chemistry is essential for the perception of the effects of THC, so one user might experience some of them in a far greater amount than somebody else. You can easily figure out how your body reacts to THC after just taking it once.

Another factor is the strain of cannabis used, as well as the concentration of THC of that particular strain, and the quantity of other cannabinoids and terpenes present in the strain in question.

Here are the main short term effects:

  • Euphoria
  • Uncontrolled laughter
  • Feeling uplifted and energetic
  • Sense of relaxation
  • Increased appetite (a.k.a the munchies)
  • Increased heart rate
  • Red eyes
  • Dry mouth (so-called cotton mouth effect)
  • Feeling drowsy and dizzy
  • Relief from pain
  • Feeling of physical heaviness
  • Decreased spatial memory (you’ll get lost more easily)
  • Decreased body temperature
  • Anxiety and paranoia (these issues tend to happen more to people who are particularly sensitive to THC)
Short term effects can be described as the immediate sensations associated with THC consumption. The intensity of these effects greatly vary from person to person.

THC benefits (medical)

Cannabis can help to treat symptoms of an astonishing number of diseases and health conditions.

Probably the most amazing use of THC is in its battle against cancer cells. The animal clinical tests have shown that the THC compound causes cancer cells to commit autophagy (or cell “suicide”), and thus stopping the proliferation and growth of certain tumors.

Also, the anti-inflammatory qualities of THC makes this natural chemical a great aid for a wide range of modern diseases that have their root cause in inflammation such as the majority of autoimmune diseases, depression and neurodegenerative illnesses.

Some of the conditions that THC (cannabis) has been proven to help include:

Cannabis is the most versatile medicinal plant known to man, and its main constituent (THC) is responsible for a colossal range of benefits, for numerous conditions that are listed above.

Long-term effects and side-effects of THC

The research on the long-term effects of THC (and cannabis in general) is still quite limited. The scientific studies conducted so far frequently offer conflicting results but there is general agreement on some negative long-term effects of THC use..

Increased tolerance

If you frequently consume large quantities of cannabis, your body becomes more tolerant to THC and other cannabinoids. This means you’ll need to consume larger amounts of cannabis to achieve the same effect, and for genuine pot-lovers this is a very frustrating occurrence.

The best and only way to decrease your tolerance levels is to take a break from THC, and your sensitivity to cannabinoids will quickly recover.

General lack of interest

This is another issue that happens to users who excessively consume THC, and the feelings of apathy and emotional numbness can really interfere with your everyday life. You can fix this issue very easily by giving your body a brief period of time to recuperate from excess THC (7 days should be more than enough).

Problems for those predisposed for psychotic disorders

This particular study showed that frequent THC consumption in people who have a genetic predisposition to schizophrenia and other forms of psychosis can cause the initial symptoms of psychosis to develop earlier.

This is definitely a very bad thing, so if you’re at risk of such illnesses, you should stay away from tetrahydrocannabinol.

Altered memory

One study found that users who frequently enjoy THC experience a slight decrease of verbal memory over long periods of time. This may sound somewhat frightening, but the research showed that (on average) hard-core stoners lose only one word over a period of five years.

It’s essential to note that it’s utterly impossible to have a THC overdose.

An important thing that differentiates cannabis (and THC) from substances such as opioids, is that the receptors of the ECS aren’t stationed in the parts of the brainstem that control breathing. Because of this, too much THC cannot cause serious harm to any of our vital organs.

Scientists have calculated that a person would have to consume 40,000 times more THC than an usual dose (a joint) to overdose on it, which is just undoable in reality, so you can relax and be certain that you’re safe no matter how much THC you’ve ingested.

Another reassuring fact is that this particular study showed no measurable brain damage from THC in adults.


This is not a problem which is directly connected with THC, but rather with smoking cannabis. Even if you’re smoking pure pot with organic rolling papers, over the course of an extended period of time you’ll most likely develop some sort of lung irritation, very commonly bronchitis.

This has nothing to do with THC (or weed for that matter), but is a problem with inhaling burned organic matter since combustion releases unhealthy carbon particles. These issues can be avoided by changing the way you consume cannabis (vaping/edibles being the best options for lung-health).

Prolonged exposure to THC can create several different effects including increased tolerance, feeling of apathy and a slight decrease of verbal memory. Also, people who are genetically predisposed to mental illnesses should avoid THC.

How to consume THC

All marijuana strains and species contain tetrahydrocannabinolic acid, or THCA, and we can consider that THCA is the THC compound, but in its raw natural form.

In its raw form, THCA cannot bind to the receptors of the endocannabinoid system, because it has one atom of carbon that’s stopping it to fit to the receptors of the ECS.

This is why nothing happens when we eat a bud.

In order for us to feel the effects of THCA, heat needs to be applied to cannabis, which removes the excess carbon atom from the THCA compound, and transforms it into the good old psychoactive and medicinally beneficial THC.

This process is called decarboxylation, and it functions exactly the same no matter if you’re smoking, vaping, making canna-butter, or consuming more potent forms of cannabis.


Even though these are the two most prominent cannabinoids found in cannabis, they share very little resemblance. THC is found in much larger quantities than CBD (or cannabidiol), and unlike THC, cannabidiol doesn’t create any mental effects (it’s completely non-psychoactive).

These two chemicals also have a different way of interacting with our bodies.

THC produces its effects by binding to the receptors of our endocannabinoid system, and these receptors, once affected by THC, inform other parts of the ECS to perform various chemical tasks within the body.

CBD, on the other hand, has a completely different approach. It restricts the fatty acid amide hydrolase enzymes (FAAH) which are in charge of destroying our internal endocannabinoids (including anandamide), which then boosts the quantity of our endocannabinoids.

Besides the FAAH restriction, CBD also affects us in a couple of completely diverse ways, from activating our 5-HT1A hydroxytryptamine serotonin receptors (wonderful for anxiety), and TRPV1 receptors (great for mediation of pain perception, body temperature and inflammation).

CBD also diminishes the psychoactive effects of THC, which facilitates the medical benefits of tetrahydrocannabinol, because large doses of THC are known to cause feelings of paranoia and anxiety.

The combination of these two cannabinoids is amazing for treating illnesses and health conditions, because they play so well off each other.

Even though THC and CBD are very different and they access the endocannabinoid system through different “pathways”, they both have their own unique beneficial effects, but also cooperate great together, maximizing their therapeutic potential.

Read next: CBD: the Complete Science Behind Cannabidiol (Feat. Martin A. Lee)

About the author
Marco Medic

A passionate cannabis enthusiast, Marco mainly writes about the latest research on cannabis use in health.

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