top of page
Search

How Weed Changes the Brain: Debunking Misconceptions

  • Brittany
  • Nov 5, 2023
  • 7 min read

Since cannabis’ legalization in Canada in 2018, the amount of questions I’ve received about its usage has skyrocketed. Typically, it's some variation of “I’ve heard weed is supposed to help with anxiety, so why does it make me feel so anxious?” or “Why did marijuana make me feel great before and not so great anymore?” These questions are good ones to be asking, especially since the research in this area has been slow to evolve. Anecdotally, some people will notice that cannabis helps with their anxiety in the moment. That means they use it when they feel stressed or anxious and then feel relaxed or distracted when high. However, cannabis has a different impact on our brains and bodies in the long term, especially when it is used regularly. To really understand the relationship between marijuana and anxiety, let’s take a look at studies that have followed participants over a long period of time.


The Relationship Between Cannabis and Anxiety


First of all, we know there is an established connection between anxiety and cannabis. Research from before legalization showed that frequent cannabis users consistently are more likely to have an anxiety disorder, and that people with an anxiety disorder are more likely to use cannabis¹. A very large study followed over 3000 young adults from birth until they were 21 years old. Those who regularly used marijuana from ages 15-21 were much more likely to experience symptoms of anxiety disorders in early adulthood². Earlier this year, a group of researchers did the heavy lifting for us and analyzed 24 different studies on cannabis use and anxiety. They came to the same conclusions: that cannabis use was significantly associated with increased likelihood of developing an anxiety condition³. This means that smoking/absorbing/vaping/eating marijuana products puts you at greater risk for developing anxiety, especially if it’s used long-term. So, what’s considered “long term usage”? Researchers have found that regular use over a period of 6 months is enough to increase anxiety symptoms⁴. If you yourself are a long-term user, you may have noticed that you experience more anxiety or paranoia when it comes to yourself, others, or your health more than you used to. Some may notice that they have more anxious thoughts; others may notice their anxiety in their body. For example, their body is quicker to shake when they are stressed, they’ve experienced panic attacks more often, or their heart races more quickly than it used to when feeling nervous. If you have experienced any of this, research tells us you’re certainly not alone in that experience.


What’s the takeaway?


By this point you might be wondering something like, “Maybe people with high anxiety are just more likely to seek out weed as a possible way to self-medicate. Just because weed users are more likely to have anxiety, doesn’t mean weed causes anxiety.”


This is true- we can’t say for sure that it causes anxiety symptoms. Following that thought then, maybe they are anxious and turning to weed in hopes that it will reduce their anxious symptoms, thoughts, or feelings. These studies show that even after long term use, anxiety symptoms are just as present (and they actually increase). So, we know that, even if people are using cannabis in the hopes that it improves their anxiety, it doesn’t seem to be working how they’d like it to. In fact, when people reduced how much cannabis they were consuming, their anxiety and depression actually reduced, too⁵.

The Highs and Lows of THC


By now, you might be wondering something like, “Ok, these are general statements. We know that there are different strains and potencies of cannabis, and you might be lumping THC and CBD together here. Does the potency make a difference?” Yes, yes it does, you informed consumer of research, you!

Up until this point, the cannabis we’ve been talking about has included some form of the psychoactive component known as THC (tetrahydrocannabinol). It’s THC that is responsible for that feeling of intoxication known as being “high.” When drug tests are testing for marijuana usage, it’s THC that they are detecting in the blood stream or urine. THC is linked to anxiety, physical and mental sedation, and psychotic symptoms like delusions⁶. Part of its link to these symptoms has to do with the fact that it triggers the release of dopamine, a neurotransmitter in our brain that is part of the reward pathway. Unfortunately, sometimes too much of a good thing can be a problem: the "dopamine hypothesis of schizophrenia" suggests that the psychotic symptoms of schizophrenia (like hearing or seeing things that aren't there) are caused from too much dopamine.


When it comes to THC and its negative effects, part of the problem is the strength or potency of the THC content. At very low doses, THC may help reduce anxiety responses by triggering a relaxing or euphoric state, but at high doses it creates problematic effects like the ones mentioned above⁷. So, what’s a high dose? Studies have found that products with THC doses of 10mg or more can increase anxiety and produce a psychotic effect, while a low dose would be considered around 1.0 to 5.0 mg of THC⁸. Part of the problem some people encounter when it comes to THC is that they keep increasing the amount they’re taking. By increasing the strength of their cannabis, they might unintentionally be causing more harm than good.


Why do people increase their THC doses?


Some people are likely to increase their THC doses because they feel they’ve developed a tolerance and no longer get the same “high.” To understand that, we turn our attention to what THC actually does to our bodies. Chemicals in cannabis bind to certain receptors in our body called cannabinoid receptors. Normally, it's our brain’s natural chemical called anandamine that will bind to these receptors, but the structure of THC is similar enough to bind to them as well. These cannabinoid receptors are found throughout our brain and nervous systems⁹. We have a lot of these receptors in our body because they play a role in motivational, emotional, and affective processing. With continued cannabis use, the body starts to reduce the amount of cannabinoid receptors available¹⁰. This “downregulation” is part of the body maintaining balance and making up for the influx of THC. To oversimplify it: over time, the build up of THC in our blood causes receptors to disappear. Cannabis at first binds to all our cannabinoid receptors, then with regular use our body starts to get rid of some of those receptors, which leads to people experiencing differences in how their minds and bodies react to cannabis. Regular cannabis users might be increasing their doses because they are trying to achieve the same type of high they once got; however, the facts are they just don’t have the same receptor sites they used to.


What’s CBD?


CBD, on the other hand, is another type of cannabinoid found in cannabis. It’s CBD that’s been shown to be safe and well-tolerated by healthy people¹¹ and it doesn’t produce the psychoactive effects that THC does. In other words, people don’t get a feeling of being “high” from CBD. Research has shown that people taking only CBD do not report feeling intoxicated¹². When studies talk about the benefits of cannabis, it’s generally CBD they’re referring to. For example, studies have found that CBD has been useful in the treatment of anxiety disorders¹³ and epilepsy¹⁴. While it’s not without its risks, it doesn’t seem to be connected to developing anxiety, delusions, or paranoia like its THC counterpart.


 

Here's the "Too Long; Didn't Read" of it:

  • High doses of THC (typically over 10mg) over long periods of time are linked to the development of anxiety, paranoia, hearing voices other people can't hear, and seeing things that are not really there. Lower doses (1 to 5mg) are not as likely to have negative effects.

  • THC builds up in the blood, which shuts down some of our brain and body's receptors over time, and can lead people to experience different highs than they used to have.

  • When people stop consuming THC, these receptors can actually come back. This means that taking a break from cannabis can help your body "undo" some of the impact THC has had on it.

  • CBD does not cause people to feel high or intoxicated. CBD and THC are not the same thing, and it's possible to have cannabis that has a high CBD content without a high THC content.

  • There's still a lot to be known about how and why cannabis affects the brain and body. Research is continuing to explore this area.


 

References

Battistella, G., Fornari, E., Annoni, J. M., Chtioui, H., Dao, K., Fabritius, M., Favrat, B., Mall, J. F., Maeder, P., & Giroud, C. (2014). Long-term effects of cannabis on brain structure. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 39(9), 2041–2048. https://doi.org/10.1038/npp.2014.67


Boggs, D., Nguyen, J., Morgenson, D. et al. Clinical and Preclinical Evidence for Functional Interactions of Cannabidiol and Δ9-Tetrahydrocannabinol. Neuropsychopharmacol. 43, 142–154 (2018). https://doi.org/10.1038/npp.2017.209

Crippa, J. A., Zuardi, A. W., Martín-Santos, R., Bhattacharyya, S., Atakan, Z., Mcguire, P., & Fusar-Poli, P. (2009). Cannabis and anxiety: A critical review of the evidence. Human Psychopharmacology: Clinical and Experimental, 24(7), 515-523. doi:10.1002/hup.1048 Freeman AM, Petrilli K, Lees R, Hindocha C, Mokrysz C, Curran HV, Saunders R, Freeman TP. How does cannabidiol (CBD) influence the acute effects of delta-9-tetrahydrocannabinol (THC) in humans? A systematic review. Neurosci Biobehav Rev. 2019 Dec;107:696-712. doi: 10.1016/j.neubiorev.2019.09.036. Epub 2019 Sep 30. PMID: 31580839. Hayatbakhsh, Najman, Jamrozik, Mamun, Alati, and Bor (2007). Cannabis and Anxiety and Depression in Young Adults: A Large Prospective Study, Journal of the American Academy of Child & Adolescent Psychiatry, Volume 46, Issue 3, Pages 408-417. doi.org/10.1097/chi.0b013e31802dc54d.


Hser, Y., Mooney, L. J., Huang, D., Zhu, Y., Tomko, R. L., Mcclure, E., . . . Gray, K. M. (2017). Reductions in cannabis use are associated with improvements in anxiety, depression, and sleep quality, but not quality of life. Journal of Substance Abuse Treatment, 81, 53-58. doi:10.1016/j.jsat.2017.07.012


Mammen, G., Rueda, S., Roerecke, M., Bonato, S., Lev-Ran, S., & Rehm, J. (2018). Association of Cannabis With Long-Term Clinical Symptoms in Anxiety and Mood Disorders. The Journal of Clinical Psychiatry, 79(4). doi:10.4088/jcp.17r11839


Raymundi, A.M., da Silva, T.R., Sohn, J.M.B. et al. Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies. BMC Psychiatry 20, 420 (2020). https://doi.org/10.1186/s12888-020-02813-8


Skelley, J. W., Deas, C. M., Curren, Z., & Ennis, J. (2020). Use of cannabidiol in anxiety and anxiety-related disorders. Journal of the American Pharmacists Association, 60(1), 253-261. doi:10.1016/j.japh.2019.11.008

Stott, C. G., Nichol, K., Jones, N. A., Gray, R. A., Bazelot, M., & Whalley, B. J. (2019). The Proposed Multimodal Mechanism of Action of Cannabidiol (CBD) in Epilepsy: Modulation of Intracellular Calcium and Adenosine-mediated Signalling. Epilepsy & Behavior, 101, 106734. doi:10.1016/j.yebeh.2019.08.009


Xue, S., Husain, M. I., Zhao, H., & Ravindran, A. V. (2020). Cannabis Use and Prospective Long-Term Association with Anxiety: A Systematic Review and Meta-Analysis of Longitudinal Studies. The Canadian Journal of Psychiatry, 070674372095225. doi:10.1177/0706743720952251

 
 
 

Comments

bottom of page