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THC exposure has long-term effects on the dopamine system

According to the researchers, there is now “substantial evidence” in animal and human studies that long-term exposure to THC leads to a decrease in levels of dopamine.

“The available evidence indicates that THC exposure produces complex, diverse and potentially long-term effects on the dopamine system,” the authors explain. “These include increased nerve firing and dopamine release in response to acute THC, and dopaminergic blunting associated with long-term use.”

The team believes this effect may explain why people who engage in long-term marijuana use are at increased risk for mental health problems.

In animal models, current research shows that marijuana use initially raises dopamine levels, fueling a sense of reward, which the team says may offer an explanation for why some users become addicted to the drug.

However, the authors point to some limitations in this area. “Fundamentally, animal studies are too short, and don’t give cannabis repeatedly or in combination with other substances,” notes Prof. Howes.