Think about the first time you smoked marijuana versus the most recent time you did so. Was the experience different? Probably. But why was that? Well a group of scientists believe they know why.
A study published in a neuroscience journal attempts to explain the long-term affects of using marijuana. Scientists know that using marijuana, as well as many other drugs or activities, causes a release of dopamine in a person's brain, which leads to a feeling of pleasure or euphoria. But scientists at Brigham Young University wanted to see if long-term use of marijuana would affect dopamine release.
The scientists conducted an experiment where they analyzed dopamine release in mice. One group received only one dose of THC, the compound in marijuana that causes dopamine release, and one group received an injection every day for a week. They found that in the group that received a THC injection every day, the mice released more dopamine than those who only got the single dose during the week. The reason is that continual use of THC prevents a neurotransmitter called GABA from operating. The GABA neurotransmitter regulates how much dopamine is released at a time. So when GABA is prevented from performing its duties, a person is flooded with more dopamine than they would normally.
So that sounds good, right? The more THC you consume, the happier you get. Well, maybe not. The scientists said that this phenomenon can lead to "cannabis use disorder," a condition where a person experiences negative effects from not using marijuana for a significant amount of time. It's similar to withdrawals for other drugs. While a person isn't technically "addicted" to marijuana, it means they still undergo some negative side effects if they don't regularly use marijuana.
It should be noted that this study only examined what happened when teen mice were subjected to injections of THC. The effects on adult mice could differ, and obviously the same could be true for humans as well. But it's still an important insight into how marijuana use can affect a person's brain.