What happens to your brain when you get high

If you were around in the United States in the 80s and 90s, you may remember the classic anti-drug advertisement, “This is your brain on drugs.” In the short television ad, we see an egg and are told, “this your brain.” Then the egg is cracked into a frying pan and the “brain” gets fried as the narrator declares: “This is your brain on drugs. Any questions?”

Well, we’ve got a lot of questions. But instead of oversimplifications in frying pans, let’s look to the research for answers. 

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How cannabis interacts with your brain 

Cannabis interacts with your brain via the endocannabinoid system (ECS). The ECS is primarily responsible for maintaining balance — or homeostasis — in many of our bodily functions, such as sleep, hunger, pain, inflammation, mood, and memory. 

The ECS contains receptors throughout the body, including the brain, which can be activated by endocannabinoids — natural chemicals produced by our bodies — but also cannabinoids from the cannabis plant. 

Once absorbed into our bloodstream, these chemicals in cannabis, like THC and CBD, are distributed throughout the body where they can cause some impressive effects. 

When THC or CBD trigger reactions in the brain, they can lead to a wide variety of effects, such as slight changes in coordination, euphoria, or feeling anxious, relaxed, disoriented, confused, or “high.” Your memory can be impaired, and pain or nausea may be relieved or heightened depending on the dose. 

What does THC do to your brain?

THC is particularly relevant because it activates CB1, a receptor found in many regions in the brain like those responsible for memory (the hippocampus) and emotion (amygdala). When THC reaches those receptors, it starts a chain reaction that alters certain processes and signals in the body¹

These processes can also influence neurotransmitters that affect your mood, sleep, and pain, like GABA, dopamine, and serotonin. This is what causes many of the effects cannabis can have, including pain relief, relaxation, and the euphoria we usually describe as a “high.” ^{2 3}

CBD, another prevalent cannabinoid in cannabis, works a little differently. CBD can block part of THC’s effect, altering how it impacts the brain and lessening its disorienting psychotropic effects.⁴

In addition, CBD can increase anandamide — known as the “bliss molecule” — by decreasing certain enzymes that break it down.⁵

Cognitive effects of cannabis 

While there is some evidence that mild cognitive impairment can result for chronic users, the data is fairly inconclusive. Some studies show no difference at all between cannabis users and non-users, while other studies have found mild deficits for long-term cannabis users. Notably, these cognitive impairments are far less intense than what we see with alcohol in both the short and long term.⁶

There is also evidence that suggests some medical cannabis users, such as those with ADHD or Tourette’s, may do better cognitively using cannabis than abstaining from it.  Furthermore, if it helps conditions such as chronic pain, depression, anxiety, or other chronic diseases that impact cognition, it may have a beneficial impact.⁷

Cannabis can impact people differently, depending on a number of variables, including brain chemistry, which is largely determined by genetics. Those who say “cannabis just isn’t for me” may be on the right track, since it may be a matter of genetics and endocannabinoid tone. 

Can marijuana lead to long-term damage? 

While cannabis doesn’t actively kill brain cells like alcohol does, researchers have voiced concerns about its effects on the brain. For one thing, some studies show changes like grey matter reduction to certain parts of the brain. These changes weren’t tied to functional differences between cannabis users and non-users, but it is well established that grey matter is a very important tissue in the brain.⁸

Effects of marijuana on teenage brain

There has also been some evidence suggesting that adolescent cannabis use before age 16 is tied to lowered IQ (by up to 6 points) later in life. Other studies using twins, where one twin uses cannabis and one doesn’t, found that these drops in IQ aren’t necessarily correlated with cannabis use — but might be related to other factors that lead to both lowered IQ and higher rates of cannabis use. 

Still, THC can be addictive for approximately 10% of users because of how it stimulates reward centers in the brain. Evidence suggests that young teens may be more susceptible to the addictive qualities of cannabis than older teens and young adults. Cannabis use has also been tied to an increased risk of developing certain mental conditions like schizophrenia — at least for those who are already genetically predisposed.⁹

Potential positive effects

On the other hand, there is also evidence that cannabis can have positive effects on the brain. One study found that long-term cannabis use leads to increased connectivity between certain parts of the brain, which may help compensate for other cognitive deficits it causes. Other studies show cannabis use can decrease Aβ peptides in the brain, a factor that contributes to Alzheimer’s disease.^{10 11}

A final consideration is that not all cannabis is created equally. Different chemovars may contain drastically different cannabinoids and terpenes. Therefore the effects and risks of one type of cannabis could be very different from the effects and risks of consuming another.

So does using cannabis use help or hurt the brain? It certainly won’t fry it like an egg in a hot pan, but the impacts can often depend on who is using it, how they’re using, why they’re using it, and the type of cannabis they’re using.

1. Leslie Iversen, Cannabis and the brain, Brain, Volume 126, Issue 6, June 2003, Pages 1252–1270, https://doi.org/10.1093/brain/awg143
2. Covey, D. P., Mateo, Y., Sulzer, D., Cheer, J. F., & Lovinger, D. M. (2017). Endocannabinoid modulation of dopamine neurotransmission. Neuropharmacology, 124, 52–61. https://doi.org/10.1016/j.neuropharm.2017.04.033
3. Haj-Dahmane, S., & Shen, R. Y. (2011). Modulation of the serotonin system by endocannabinoid signaling. Neuropharmacology, 61(3), 414–420. https://doi.org/10.1016/j.neuropharm.2011.02.016
4. Chye, Y., Christensen, E., Solowij, N., & Yücel, M. (2019). The Endocannabinoid System and Cannabidiol’s Promise for the Treatment of Substance Use Disorder. Frontiers in psychiatry, 10, 63. https://doi.org/10.3389/fpsyt.2019.00063
5. Leweke, F. M., Piomelli, D., Pahlisch, F., Muhl, D., Gerth, C. W., Hoyer, C., Klosterkötter, J., Hellmich, M., & Koethe, D. (2012). Cannabidiol enhances anandamide signaling and alleviates psychotic symptoms of schizophrenia. Translational psychiatry, 2(3), e94. https://doi.org/10.1038/tp.2012.15
6. Leslie Iversen, Cannabis and the brain, Brain, Volume 126, Issue 6, June 2003, Pages 1252–1270, https://doi.org/10.1093/brain/awg143
7. Cooper, R. E., Williams, E., Seegobin, S., Tye, C., Kuntsi, J., & Asherson, P. (2017). Cannabinoids in attention-deficit/hyperactivity disorder: A randomised-controlled trial. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 27(8), 795–808. https://doi.org/10.1016/j.euroneuro.2017.05.005
8. Yücel M, Solowij N, Respondek C, et al. Regional Brain Abnormalities Associated With Long-term Heavy Cannabis Use. Arch Gen Psychiatry. 2008;65(6):694–701. doi:10.1001/archpsyc.65.6.694
9. Sven Andréasson, Ann Engström, Peter Allebeck, Ulf Rydberg, CANNABIS AND SCHIZOPHRENIA A Longitudinal Study of Swedish Conscripts, The Lancet, Volume 330, Issue 8574, 1987, Pages 1483-1486,https://doi.org/10.1016/S0140-6736(87)92620-1
10. Harding, I., Solowij, N., Harrison, B. et al. Functional Connectivity in Brain Networks Underlying Cognitive Control in Chronic Cannabis Users. Neuropsychopharmacol 37, 1923–1933 (2012). https://doi.org/10.1038/npp.2012.39
11. Cao, C., Li, Y., Liu, H., Bai, G., Mayl, J., Lin, X., Sutherland, K., Nabar, N., & Cai, J. (2014). The potential therapeutic effects of THC on Alzheimer’s disease. Journal of Alzheimer’s disease : JAD, 42(3), 973–984. https://doi.org/10.3233/JAD-140093

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