The Chemistry of Weed Addiction for Non-Science Types
In this article we’re going to go a little deeper into the chemistry of what’s going on in your brain when you’re on weed. If you haven’t read “This Is Your Brain on Weed” yet, go back now and learn about that fascinating feature of our neurological system: the reward system, which is composed of the stop and go systems. At the end of the last article, I asked you which one of those two systems you think goes nutso when someone becomes addicted to a drug? Did you think it was the go system? If so, you are correct.
When the brain rewards us by making our neurons release dopamine, we feel pleasure, and the go system switches to the on position. Then the stop system jumps into action, moderating the go system. If we didn’t have stop systems to put the brakes on our go systems, the go system would morph into a positive feedback loop that required more and more pleasure. This would eventually kill the organism, meaning it would kill us.
The Effects of Smoking Weed
When we’re talking about marijuana, as well as other psychoactive drugs, weed works the go system by causing dopamine to be released from neurons like rain from a winter cloud in Seattle. How does weed do that? Well, the diagram below shows exactly how marijuana accomplishes that feat. It’s a little complex, but we’re going to take it easy like and walk through it one panel at a time, from left to right.
Graphics Source: en.wikibooks.org
In the first panel, we have our yellow neuron in the upper right-hand corner. But it can’t release any dopamine because the inhibitory neurotransmitter (the blue triangles) released by the blue neuron in the upper left-hand corner are plugging up all the dopamine release valves in the yellow neuron. (As you probably guessed, inhibitory neurotransmitters belong the stop system and dopamine belongs to the go system.)
Now let’s look at the second panel. The reverse situation is going on. Anandamide (the blue elongated hexagon) blocks the release valves of the inhibitory transmitter (the blue triangles) from the blue neuron. (Anandamide, by the way, is a naturally-occurring fatty acid molecule that is floating around in the brain and present in some foods such as chocolate. It’s known as the bliss molecule.) With those pesky inhibitory transmitters temporarily cooped up in the blue neuron, the yellow neuron can release little yellow balls of dopamine to its heart’s delight. The pink neuron on the bottom has receptors that are shaped in such a way that only dopamine will fit into them. When those yellow balls find their way to the dopamine receptors on the pink neuron, we feel pleasure.
THC blocks inhibitory transmitters from being released
The third panel depicts THC, an anandamide impostor, in the form of a green hexagon. So, instead of the naturally-occurring anandamide molecule preventing the inhibitory transmitters from being released, THC is doing the blocking. (THC, as you probably already know, is the active ingredient in marijuana.)
Graphic Source: en.wikibooks.org
In summary, THC mimics anandamide. With marijuana use, this anandamide-mimicking substance THC is introduced into the brain faster and at much higher levels than anandamide. Thus, lots of dopamine is released and then lots of intense pleasure is felt. That is to say that the go system is artificially kicked into overdrive, steamrolling over any attempts made by the stop system to moderate the situation.
How does this create drug tolerance and addiction? Well, even though the stop system becomes totally ineffective during drug use, the brain eventually becomes accustomed to the mega-doses of dopamine and compensates. This is the way our nervous system works. It is constantly making fine-tuned adjustments to our body in order to achieve equilibrium. The Niagra Falls of dopamine that occurs when you smoke pot causes major disequilibrium.
Is Weed Addictive?
Remember, the more your brain rewards a behavior with dopamine, the more you will perform that behavior. A user will want to smoke weed again because his brain is reinforcing and rewarding that action by releasing oodles of dopamine. Eventually, the brain adapts to the THC blocking the inhibitory neurotransmitter by dialing down the release of dopamine. Brilliant, isn’t it? Except now more weed has to be used in order to get the same effect. Again the brain eventually adjusts to the situation. And the user smokes more weed to compensate. And so on and so on.
Meanwhile, all this upping-the-ante business is doing damage to the neurological system. And even when not high, the reward system is acting real stingy with the dopamine. It’s dialed itself down, but it’s not dialing back up even when there’s no THC around. (This is thought to be temporary situation, thank goodness.) It’s easy to see how using weed becomes less about getting high and more about getting dopamine levels up to par. Low dopamine levels make you feel crappy. Thus, smoking weed is better than feeling crappy. This is the cycle of addiction.