That Neuroscience Guy - The Impact of Marijuana on the Brain

Episode Date: September 25, 2022

Marijuana has seen increased support, and even legalisation, around the world in recent years. But how does Marijuana use affect the brain? In today's episode of That Neuroscience Guy, we discuss how using Marijuana affects the brain. 

Hi, my name is Olof Kergolsen, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to the podcast. In the past, we've talked about the impact of alcohol on the brain, but there are a lot of other things that we can consume that can mess up our brains. brain, but there are a lot of other things that we can consume that can mess up our brains. Over the past 10 years or so, marijuana has gone from something that was illegal and shunned mostly to a drug that is mainstream and legal in many parts of the world. On today's podcast, the impact of marijuana on the brain.

I have to stay at the outset that while I know a fair bit about the impact of marijuana on the brain and the neuroscience behind it, I cannot provide you with any practical experience as I have never been high. A disclaimer, but I think it's fair to mention it. Further, my comments here are based on neuroscientific and medical knowledge and they're not an opinion. There are definitely people in the world that are pro-marijuana and that is an opinion that you're entitled to have. I'm just going to give you the neuroscience and what medicine tells us. All right, let's start with the basics of brain function. Our brains, as we know, are mostly comprised of billions of neurons. And it's the communication between these neurons that gives

rise to our senses, our thoughts, our movements, and our emotions. Last week, we reviewed the communication between neurons when we talked about synaptic plasticity. But again, in brief, neurons communicate through an electrical to chemical to electrical process. When a neuron fires, an electrical signal is sent, and that electrical signal arrives at the axon terminal, basically the end of the neuron, if you will. And when that electrical signal gets to the end of the neuron, the result of that is a release of neurotransmitter. So what is neurotransmitter? Well, we've talked about it before, but neurotransmitters are basically chemical compounds. Glutamate is the most common neurotransmitter in the brain. The chemical formula is C5H9NO4.

This isn't a chemistry podcast, so let's leave the chemistry part there. But it is, like I said, the most abundant neurotransmitter in the brain. And it's estimated to play a role in approximately 90% of all synaptic connections. But what do neurotransmitters actually do? Well, like I said, when that electrical signal, the action potential arrives at the end of the axon, at the axon terminal, it causes a release of neurotransmitter. And that neurotransmitter diffuses across the synapse. causes a release of neurotransmitter. And that neurotransmitter diffuses across the synapse.

That's the gap between the neurons, sometimes called the synaptic cleft. And basically, you can imagine this chemical substance just sort of floating around there. And thanks to diffusion gradients and properties like this, the neurotransmitter makes its way across the synapse where it binds. Think of a jigsaw puzzle fitting in. So the neurotransmitter basically is like a chemical compound, and the way binding works is it sort of locks into what

we call a receptor site. Now, when this binding happens, the chemical to electrical process generates electricity, a small excitatory or a small inhibitory postsynaptic potential, and that's what causes the next neuron to fire. So neurotransmitters play a key role in the transmission of the electrical signals that in some lead to our brain doing what it does. Now, there are dozens of neurotransmitters, some like glutamate and GABA are widely distributed across the brain, whereas other neurotransmitters like dohamine and serotonin and norepinephrine

are more focused in specific neural regions. Now, this is beyond the scope of this episode, but the reason for all the different types and different levels of focus boils down to needing different neurotransmitters for different jobs. So each neurotransmitter has a specific role to play. In the case of glutamate, for instance, it's just a primary transmission neurotransmitter has a specific role to play. In the case of glutamate, for instance, it's just a primary transmission neurotransmitter that works for most neurons. But dopamine, as we've talked about in the past, plays a key role in the learning process, norepinephrine in the decision-making process. So each neurotransmitter sort of has its own separate role or job to play. Now, there's more to it than neurotransmitters. There's also

neuroregulators. So what's a neuroregulator? Well, they're effectively compounds that modulate neurotransmission and neurotransmitters. Think of a neuroregulator as something that controls the neurotransmitter to some extent. So we're going to come back to this, but let's get into marijuana because we're already a couple minutes in and I haven't said much about it. Well, marijuana and its impact impacts the most extensive neuroregulatory system in the human brain, and that's the endocabininoid system. Now, the ECS, I'm going to abbreviate it so Matt doesn't have too many redos to deal with on this podcast, is still being studied. But the endocabininoid system plays a major role in motor control, so movement, motor

coordination, learning, memory, emotion, motivation, addictive-like behavior, and pain modulation. So this neuroregulatory system, the endocabininoid system, plays a massive role in controlling the neurotransmitters that underlie these processes. But what do neuroregulators like the ECS system actually do? I said they control things, but how? Well, in brief, the ECS system controls the neurotransmitter system. And what it does is the ECS system can slow down the release of glutamate, which reduces neuronal firing, or it can act to inhibit GABA neurons, which results in an increase in firing rate.

So in other words, by changing the way the ECS system is working, it can basically reduce firing or increase firing for different neurotransmitters. So in other words, the ECS system is a control system for the brain. And how is this control implemented? A key part of this regulation involves endocabininoids, which are the key compound involved in the regulation process. So when endocabininoids are released, that might result in a reduction in firing rate for the glutamate system or an increase in firing rate by inhibiting cabinet neurons. In the rest of the body, endocabinoids do things as well. They play an important role in relaxing muscles, they reduce inflammation, they protect damaged tissue, and they regulate appetite and metabolism, and amongst many other things.

Now, this is all more complex than this, if you get into the neurochemistry of this. And we could dive into the different types of cannabinoid receptors, for instance, but I said this is not a chemistry podcast. And to be honest, I wasn't that great at chemistry back in the day, so let's stick to neuroscience. All right, finally, so how does marijuana impact the ECS system? Well, the principal ingredient of marijuana is TCH, tetrahydrocannabinol, which is at least one of 113 cannabinoids which have been identified from the cannabis plant. So when you consume marijuana, you're basically consuming TCH. Now, without getting back into a description of the chemical binding process,

what TCH is effectively doing in the ECS system is it's latching onto the cannabinoid receptors, and as a result, it blocks what the endocannabinoids can do. So in other words, the TCH is blocking the regulatory system so it doesn't function effectively. Let's review how that works just to make sure we get it. And normally, endocannabinoids are released, right? And they help regulate the firing of glutamate and GABA and other things. But when TCH comes in, it's going to bind to the receptor sites where the endocannabinoids normally bind,

thus blocking brain regulation to some extent. So that's how it impacts your brain function. For example, your short-term memory is impaired when you're high because TCH slows down neurotransmission in the hippocampus. It also can impact the motor system for the same reason, because TCH impacts primary motor areas in the cerebellum, and specifically those endocannabinoid receptors, and as a result, people that are high become less coordinated. But there's also positives to TCH in the ECS as well. They impact pain receptors, which is why marijuana is a prescribed drug for chronic pain. One thing to note here is that TCH does not impact the brainstem to any major extent,

so there is no impact on respiration. So there are a lot of places across the brain where TCH has an impact. In the amygdala, the blocking basically toys with your emotions, and that's why you can experience panic or paranoia when you're high. In the basal ganglia, it slows your reaction time because it's blocking movement initiation in the striatum. In the brainstem, I said it doesn't do much, but it does have an anti-nausea effect, but it doesn't block breathing. In the cerebellum, I've already mentioned it, TCH can impair coordination. In the hippocampus, it can impair memory.

In the hypothalamus, it results in increased appetite. And that's actually why you get the munchies. A lot of people that are high say they have the munchies, and that's because TCH is blocking receptors in the hypothalamus that suppress appetite, and it actually results in increased appetite. In the neocortex, which is the prefrontal cortex, and those sort of regions, the blocking basically alters your thinking patterns and your judgment and sensation.

In the nucleus accumbens, the blocking results in a sense of euphoria. And finally, in the spinal cord, the blocking from the endocannabinoids or the blocking of the endocannabinoids results in altered pain sensitivity. Okay, but what about the negative consequences? There is a bad side to this. Now, I'll point out the content I'm about to discuss comes from medical journals, and I've verified this content with some friends at the medical school here. So for those of you that are listening that are pro-cannabis, this is scientific reality. Studies show that early and high doses of cannabis basically result in an increased chance of development of psychotic symptoms. Frequent use of cannabis, especially the start of use at a younger age, doubles the risk of schizophrenia development in the future.

Daily use of marijuana increases the risk of psychotic illness and with a five times higher risk in people who frequently use high potency THC. And of course, there's the obvious things like the fact that marijuana use is a form of impairment, which is just as bad as drinking and driving. So definitely don't get high and drive. And when we get into young people and brain development, you know, and young people, the brain is still developing, the impact of marijuana is potentially even worse. It can result in altered brain development, cognitive impairment, depression, and anxiety. And while I've just pointed out some of the harsh realities to the use of cannabis, especially for adolescents, there are definite medical benefits, especially to people experiencing chronic pain.

The scientific reality is that the jury is still out, especially when it comes to long-term effects. But studies that are starting to look at the long-term effects of cannabis use and THC use specifically have found long-term memory issues, permanent anxiety issues, permanent depression issues, lower dopamine production levels, which can have an impact on learning and memory, lung damage, persistent cough, and even increases in risk for heart attacks, certain diseases, and stroke. So cannabis and marijuana is an interesting thing. There are some positives to it. Pain suppression in people, like I've said, that are chronically ill or experience extreme pain, it's an amazing thing in those situations. But it can have negative consequences as well. And basically, the summary of it is that THC that's in the marijuana, it's basically blocking your endocannabinoid system from regulating the brain properly.

All right, the neuroscience of marijuana. Remember, if you've got ideas for future episodes, we're still planning season four. You can follow me on Twitter at that neuroscience guy and DM me. Give us some show ideas. This idea, as with neuroplasticity, came from you, the listeners. Of course, you can also email us, thatneuroscienceguy at gmail.com. Our Etsy store is there, that neuroscience guy. We've got some t-shirts, which I think are hilarious, but maybe aren't as funny as I think they are. You can support us on Patreon. Thank you so much to those of you that do. Again,

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I'll see you on Wednesday for another neuroscience bite. My name is Olive Kregolson, and I'm that neuroscience guy. Thank you so much for listening.