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Why Does Cannabis Produce THC?

December 16, 2016
As we learned in an earlier installment this week, humans and most other animals have what’s called an “endocannabinoid system” (ECS). The ECS includes a network of receptors throughout the body that allow us to feel high when THC is consumed. But is that the reason we have an ECS to begin with – to get high?


What is the endocannabinoid system and what is its role?

The short answer: Nope. The cannabis-induced euphoria we feel is probably best thought of as a biological afterthought. Our ECS allows us to get high, but that’s not why we have it. We know this because the ECS existed long before humans forged any sort of relationship with the cannabis plant. In fact, the ECS was around before the cannabis plant even existed.

The Endocannabinoid System, B.C. (Before Cannabis)

Historical records show that humans have used hemp resources for over 7,000 years and have harnessed cannabis’s medical properties for at least 3,000 years. While our human bond with cannabis is no doubt an ancient one, organisms were built to interact with it long before the cannabis plant even evolved. But how do we know that?

The endocannabinoid system (ECS) is not unique to humans – it exists in all kinds of animals. Tracing the widespread development of the ECS back in time and across many different species, it’s clear that this system has played an important biological role for a very, very long time. In fact, key components of the ECS evolved hundreds of millions of years ago, long before the dinosaurs.

Major pieces of the endocannabinoid system evolved hundreds of millions of years ago. The endocannabinoid system (ECS) is widespread throughout the animal kingdom, and its major components first evolved long before humans or Cannabis existed. The major ECS receptors, CB1 and CB2, are probably present in all vertebrates (animals with a backbone), but not insects. A major ECS enzyme called FAAH has likely been around since the first animals with a nervous system evolved.

Researchers at Queen Mary University of London use knowledge of evolution and brain development to posit their theory on the possible age of the ECS:

“The expression of [the CB1 receptor] in so many different brain regions suggests that endocannabinoid signalling has been a fundamental and widely employed mechanism of synaptic plasticity throughout more than 400 million years of vertebrate brain evolution. Moreover, there is evidence that at least some of the physiological/behavioural roles of endocannabinoid signalling that have been discovered in mammals are also applicable to non-mammalian vertebrates, suggesting evolutionarily ancient origins.”

Tracking the history of cannabis evolution through its closest relatives, researchers estimate that cannabis evolved between 34 million and 6.38 million years ago, long after the ECS had evolved in animals. If the endocannabinoid system predates the earliest species of cannabis, one might wonder why the ECS first evolved. The answer lies within chemicals the body naturally produces, called “endocannabinoids.”


Cannabis Evolution: What Do We Know About the Plant’s Earliest Origins?

Maintaining Balance: Endocannabinoids and Homeostasis

The reason our ECS is so important to our overall health and wellness is because it plays a crucial role in regulating some major biological functions. Our body seeks to maintain a narrow operative balance, or “homeostasis,” and cannabis-like compounds can help our bodies achieve this equilibrium which is so critical for our health.

Our ECS was built for natural compounds produced by the body. Endocannabinoids are molecules created by cells to regulate biological functions in the body and brain. Anandamide and 2-AG are the two major endocannabinoids.

The CB1 receptor, a major player in the ECS, is the receptor responsible for initiating THC’s psychoactive effects. But the CB1 receptor doesn’t exist for the purpose of allowing THC to get us high—it exists so that endocannabinoids like anandamide and 2-AG can activate it as part of the body’s constant effort to maintain homeostasis. With this critical function in mind, it isn’t difficult to see why it is that the ECS evolved so long ago. It’s been helping regulate complex biological systems since long before cannabis even existed.


Why does cannabis get you ‘high’ and make you feel good?

Why Does Cannabis Produce Cannabinoids?


If getting high isn’t the reason we have an ECS, why does the cannabis plant produce a psychoactive compound like THC in the first place? The simple answer is for survival. Cannabis grows in many different geographies and climates; from tropical, hot equatorial regions to cold, harsh mountains, cannabis has successfully adapted to a spectrum of environments with the help of protective features like cannabinoids.

Cannabinoids like THCA (which converts to THC with heat and over time) are produced in tiny glands on the surface of the plant called trichomes. Trichomes appear on many plant species and serve to protect in a variety of ways, including:

  • Defending against insect herbivores
  • Defending against frost in colder habitats
  • Minimizing water loss in windy habitats
  • Preventing of overheating in dry, open habitats
  • Attracting pollinators or prey 

What separates cannabis from a majority of other trichome-producing plants is the psychoactive properties of its constituents, namely THC. To understand why a plant makes psychoactive compounds, take caffeine and nicotine for example. Caffeine and nicotine are natural pesticides that help deter insect predators from eating these plants. So this is one potential role that a compound like THC could conceivably play: to help ensure survival by deterring predators from eating it.


What are trichomes and why do they exist on cannabis?

THC may serve another role as an anti-microbial. Plants have to worry about germs just like animals do. However, they do not have an immune system like animals, so they tend to produce chemical cocktails to help guard against infections. Raphael Mechoulam, the chemist who first isolated THC in 1967, speculated to Leafly that this may be the case for compounds like THC. “Plants do not have an immune system,” he told us. “Hence they guard themselves with specific chemicals.”

Studies do in fact show that cannabinoids, including THC, have anti-microbial properties. However, according to ethnobotanist Robert C. Clarke, the idea that THC defends against pests or microbes is not well supported by his experiences in cannabis gardens. “Pest populations can become rampant indoors under lights and in glasshouses,” Clarke said, “and the highest THC clones are no more resistant to pathogens and pest infestations than lower THC clones.”

This theory doesn’t necessarily stand in opposition to the idea that it may serve a defense function; THC might be effective at repelling only certain insect pests, or guarding against specific species of microbes but not others.


Spider Mites, Fungus Gnats, and Root Aphids: How to Deal With 3 Common Cannabis Pests

THC specifically may protect the plant from ultraviolet light. Researchers at the University of Maryland exposed cannabis plants from different areas of the world to UVB rays through irradiation and found that they produced more THC than those that were not exposed, suggesting a protective function. This kind of protective role also makes sense considering the type of environment where cannabis thrives: open areas with lots of direct sunlight.

Even though we can’t pinpoint the exact reason that cannabis evolved to produce THC or other cannabinoids, this patchwork of theories all point to some protective function for these compounds. It’s clear that they can benefit us, too, thanks to our ECS. In this way, the relationship we share with cannabis amounts to far more than getting high, but something much more vital with roots in our ancient history.


Elphick, Maurice R. “The Evolution and Comparative Neurobiology of Endocannabinoid Signalling.” Philosophical Transactions of the Royal Society B: Biological Sciences 367.1607 (2012): 3201–3215. PMC. Web. 15 Dec. 2016. [PDF]
Herkenham M, Lynn AB, Little MD, et al. Cannabinoid receptor localization in brain. Proc Natl Acad Sci USA. 1990;87(5):1932-6. [PDF]
Esra M. M. Ali; Aisha Z. I. Almagboul; Salwa M. E. Khogali; Umelkheir M. A. Gergeir. Antimicrobial Activity of Cannabis sativa L. 2012. [PDF]
Nakamura A, Osonoi T, Terauchi Y. Relationship between urinary sodium excretion and pioglitazone-induced edema. J Diabetes Investig. 2010;1(5):208-11. [PDF]

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Bailey Rahn

Bailey is a senior content manager at Leafly, specializing in strains and health. She's spent 7+ years researching cannabis products, spreading patients’ stories, and exploring healthy ways of integrating cannabis into daily life.

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  • maxwood

    The “Ethnobotany” article sets out a theory that even if phytocannabinoids predated contact with animal endocannabinoids, they increased in prominence and importance in the last few millenia when (a) humans began to exploit cannabis seed and stalks for food, thatching and cooking fires and (b) some of the seeds fell into and germinated among human dungpiles or outhouses.

  • BenSamizdat

    Cannabinoids are acids the plant makes as a defense mechanism in response to UV light.
    33 million years ago a series of asteroids smacked into our planet, creating instant deserts and floods.
    C4 plants adapted to fill the empty niche, beginning very high up in the mountains, now become islands.
    Because the mountains are so high, a large band of UVB light hits all plants.
    UVB and UVC sever DNA, forcing life at high elevations to evolve and adapt.
    Cannabis adapted pumping its resin glands full of acids that block UV light.
    This is not a question of “may”.
    Hundreds of scientific papers, magazine articles and books have been published proving that this is how it works.
    This article suggests that the researchers at Queen Mary University are on to something.
    But in reality, they are asking questions that were answered decades ago and everyone has long since moved on.
    Which makes me ask myself “what is really going on here?”
    The question this article really has, is why do those cannabinoids make people high?
    The ECS should really be called the Endo Anandamide System.
    Anandamide is used by many organisms as a reward to force them to hunt and consume nutritional elements.
    If the deep sea fish living in total darkness eats some seaweed and this is fortifying, the brain adapts to release anandamide.
    This makes the fish seek out the same or similar seaweed until the brain says “we have enough of those minerals and vitamins”.
    Cannabinoids act as agonists and antagonists for certain nerve cells.
    What we are discovering is that plaques can cover nerve cells and that cannabinoids flush out these receptors.
    This heals us, therefore our brains have adapted to say “cannabis is good!”.
    The process of evolution took at least 200,000 years and probably several million.
    This began 7 million years ago when our Chimpanzee and Bonobo ancestors left the jungle to investigate this wonderful smell.
    The smell was burning fields of cannabis that covered much of the world.
    We know this because almost ALL higher life forms have evolved to take in cannabinoids.
    That includes reptiles, birds and mammals.
    This can only have happened under forced circumstances that took place over hundreds of thousands of years.
    Hence, “burning fields” being the only explanation.
    Merry Christmas!

    • Thanks, Very Informative. You should Write a Book around this Subject and perhaps the Overall Benefits of Cannabis, Connecting the Data as well. The Article ‘feels’ Apologetic that we ‘get High’ from THC, and there is that supposed Implication that Researchers are ‘on to something new’ to make it seem Timely and Relevant to today. I’d be VERY INTERESTED in Your Book. All the Best, 😉

    • TD

      Wait. Where is the evidence about the giant burning cannibis fields?

  • Darius A Stokes

    THC is actually a great web producer a good contract with a shielding or building material or clothing can work with.Insects use it to create film or slim or material. It reflects light so there goes your invisible shielding. You just have to encode the film residue. It also shields your brain from harmful lights. Use a room just for spider mite other work well they love making silk they just don’t like being bothered and they will get big on you.

    • Hemp Association

      You are what you eat (and your thoughts).

      Essential Nutritional Cannabis/Hemp virtually eliminates Consumptive Waste. In the process, the environment for Bacteria and Virus-hosting Bacteria is greatly reduced.

      Cannabinoid Acids act as Bio-Industrial Pestilence Ridders to remove Virus-hosting Bacteria and Cannabis/Hemp Proteins Hemaggluinate Virus from the blood stream by resonating so it cannot attach to Red Blood Corpuscles. Protein, Virus-attached is passed over by the Kidneys and excreted as waste.

      This cleansing process along with re-generation and generation of nerve growth generates Genetic Expression of DNA to replace what has been referred to as “black Goo”, or infested Consumptive Waste with Plant-based Diet to fuel replacement Genetic Expression.

      (See: Bruce Lipton, PhD, Genetic Expression

      The result is the body not only embraces the sunlight and radiation, it can Regulate and Modulate these as Source Energy. Plants like the Sun. After all, the body runs on Energy, and there are examples of those who can sun gaze today and seem to run off this energy.

      I won’t even go into the manipulation of the Bacteria and Virus that result from the Food-System Diet, but here are the patents. Dr. Richard Alan Miller, A-Team is the expert on gut and bacterial manipulation. Dr Loos on the devices. Dr Lipton on Genetic Expression. Dr. Montagier on Virus & Resonance, and I am living efficacy.


      Subliminal acoustic manipulation of nervous systems
      US 6017302 A

      Nervous system manipulation by electromagnetic fields from monitors
      US 6506148 B2

  • Hemp Association

    Cannabis DOES NOT produce THC.

    THCA-Synthase is the PRODUCT of Cannabis.
    CBDA-Synthase is the PRODUCT of Hemp.

    THCA-A is the ENZYMATIC SYNTHESIS of the PRODUCT of Cannabis and CBGA.
    CBDA is the ENZYMATIC SYNTHESIS of the PRODUCT of Hemp and CBGA.

    Cannabis CANNOT produce, NOR synthesize THC.
    Hemp CANNOT produce, NOR synthesize CBD.

    THC is the Non-Enzymatic DECARBOXYLATE of the SYNTHESIS of the PRODUCT of Cannabis.


    (April, 2008 – At Fifth National Clinical Conference on CannabisTherapeutics, April, 2008 in Pacific Grove, CA. Arno Hazecamp, PhD, commission by the Dutch government’s Office of Medicinal Cannabis, researches chemical composition of cannabis tea, finding relatively high concentrations of THCA (THC Acid) rather than THC (decarboxylated).

    Video Cued:

    • John Holden Schmalz

      You’re so very wrong, it’s not even funny. Hemp is Cannabis. While academics continue disputing taxonomy, google “cannabis afghanica” and then read up, and check out wikipedia…

      Whether the plant is Cannabis sativa, Cannabis indica indica or Cannabis indica afghanica determines whether it produces THCA or CBDA or any other cannabinoids in varying amounts, but it’s all cannabis. Do Linnaeus some justice.

  • lovingc

    It is also possable that THC improves the spread and survival by being eaten (seeds) and spread in feces by birds.

  • Darius A Stokes

    THC is basically a product that’s becoming sap so that insects can use it for other products.

  • Jeff Hoke

    Still does not mean that smoking cannabis is not simply using drugs to get high.

    • misterveritas666

      So? Your point? My body, my right. Butt out.

    • Oddity

      ok, boomer

  • Plant cannabinoids are called phytocannabinoids.