Feature Story

You’ve Got Some Nerve: How Marijuana Effects the Developing Brain

With the legalization of marijuana either occuring or imminent in coutnries around the world, student as young as 17 in some jurisdictions will be able to buy a variety of forms and flavors of this once illicit drug.

Activists have hailed this great liberation as a long-awaited modernization of an antiquated law. After all, in Canada, it was the notorious fuddy-duddy William Lyon Mackenzie King (then minster of Labour, and later Prime Minister of Canada) who initiated this legislation in 1908 – at a time when ideas like antibiotics, viruses or even DNA were still decades in the future.

However, since then science has learned much about the human body and how it responds to different chemicals. In particular, we have a much better understanding of the brain and its cells (call neurons). So, dear reader, before you rush off to your local dispensary to pick up your first dose of weed, it may be worth our while to take a look at the extraordinary science of marijuana.

As with most drugs, marijuana is taken because it changes one’s mental state – to be ‘high’ as it affectionately called. Therefore it doesn’t take a neurosurgeon to appreciate that when we examine what this drugs does, we have to start with the brain.

Without doubt, the human brain is the greatest creation in nature. We often like to think of big stars or pretty waterfalls as great wonders of the world, but in sheer complexity and potency nothing in the universe can rival the human brain (as far as we know). It is this 1.4kg mass of jelly in your skull that has allowed humans to conquer this planet. It can do advanced mathematics, it can design machines that can move mountains, it has peered into the deepest reaches of the cosmos, and unlike anything else, the brain has understood the very processes by which it arose. Also, it’s your brain, at this very moment which is reading these words, comprehending their meaning, conveying to you what I’m trying to say, while at the same time regulating your heart beat, controlling your metabolism and telling your fingers to grip the pages of this paper. It is therefore difficult to appreciate how spectacular a machine that mass in your skull is, and also how complex it is to understand.

However, without belaboring the details too much – all of this complexity comes down to a group of fundamental cells called neurons. There are some 100 billion neurons in your brain. To put that into perspectives, there are as many neurons in your brain, as there are stars in the Milky Way galaxy. As a matter of comparison, an octopus – with it massive head, has to make do with about 300 million neurons or about 300 times less than we’ve got.

Were you to look at a neuron under a microscope, you’ll see that each one is a bit like a web. These long arms are the key to how a neuron works. Each one is like a tiny wire, and when triggered they can send an electrical signal down their wires (called axons) either into another neuron, or directly to a working part of the body. It’s important to note that this current is not like the electricity in your home, where a single power source drives the current, instead – axons have tiny molecular pumps all along their length. To generate a current, they move some sodium and potassium ions in and out of the axons itself and this is enough to create a negative charge that is strong enough to move along an axon.

However, unlike wires, the tips of neurons aren’t connected with each other. If they were you can imagine that would mean the whole brain would have to be a single massive cell, and you couldn’t possibly to anything specific with that arrangement. Instead, there is a tiny gap between neurons called a synapse, and this allows your brain to create millions of distinct neural pathways.

However, to get a neuron’s signal across the gap, your brain can’t use the electric system – electricity after all can’t jump across empty space – unless you’re dealing with massive voltages like in lightning. Instead, your brain uses a class of very special molecules called neurotransmitters. These special molecules like dopamine, serotonin or acetylcholine help signals to cross from one neuron to the next.

Among the many classes of transmitters, is one rather banal group called the cannabinoid system. These are normally involved in regulating processes like appetite, mood, memory and pain sensation. Again, among the great processes and molecules of the brain, these are hardly worth a footnote. However, it just so happens, by a sheer fluke of nature, that the marijuana plant produces a small amount of a molecule that is more or less like our own cannabinoid molecules. When this gets into your body, it can act like a neurotransmitter in some ways, and start to interfere with your body’s natural systems dealing with appetite, mood, memory and pain (sound familiar).

If you’re having some trouble understanding that idea, try this. By smoking weed, you are effectively pumping in extra neurotransmitters into a neural system in your brain to artificially trigger changes. Whether this is a good idea is as yet to be determined. Activists like to point out that weed is no different than many types of medications that effect the brain, and it can be very useful for people with chronic pain or mood issues. However, there is a growing body of evidence that weed may also lead to long-term brain damage, including memory loss or the triggering of seizures. Some studies have also linked smoking weed with cancer, similar to cigarettes.

In other words, dear reader, we have again come to one of those irritating circumstances where science just doesn’t have a definitive answer yet. However, as weed becomes available across the country – for better or for worse, we may finally learn the true impact of marijuana.