Chronic marijuana use can interrupt the brain's natural reward processes

Chronic marijuana use disrupts the brain's natural reward processes, according to researchers at the Center for BrainHealth at The University of Texas at Dallas.

In a paper published in Human Brain Mapping, researchers demonstrated for the first time with functional magnetic resonance imaging that long-term marijuana users had more brain activity in the mesocorticolimbic-reward system when presented with cannabis cues than with natural reward cues.

"This study shows that marijuana disrupts the natural reward circuitry of the brain, making marijuana highly salient to those who use it heavily. In essence, these brain alterations could be a marker of transition from recreational marijuana use to problematic use," said Dr. Francesca Filbey, director of Cognitive Neuroscience Research in Addictive Disorders at the Center for BrainHealth and associate professor in the School of Behavioral and Brain Sciences.

Researchers studied 59 adult marijuana users and 70 nonusers, accounting for potential biases such as traumatic brain injury and other drug use. Study participants rated their urge to use marijuana after looking at various visual cannabis cues, such as a pipe, bong, joint or blunt, and self-selected images of preferred fruit, such as a banana, an apple, grapes or an orange.

Researchers also collected self-reports from study participants to measure problems associated with marijuana use. On average, marijuana participants had used the drug for 12 years.

When presented with marijuana cues compared to fruit, marijuana users showed enhanced response in the brain regions associated with reward, such as the orbitofrontal cortex, striatum, anterior cingulate gyrus, precuneus and the ventral tegmental area.

"We found that this disruption of the reward system correlates with the number of problems, such as family issues, individuals have because of their marijuana use," Filbey said. "Continued marijuana use despite these problems is an indicator of marijuana dependence."


Center for BrainHealth



  1. Michael Conn Michael Conn United States says:

    My personal experience:
    As an Engineering Manager for multiple Engineers for decades, two key experiences stand out. The first “Heads Up” on marijuana came from a new Stanford graduate. He initially started into the Engineering program with eight personal friends from their dorm. Initially as Freshmen, then more so as Sophomores, they all tried some pot in varying degrees. This individual didn’t like the “dullness” he experienced for some time after smoking and stopped using. Some of the eight indulged more than the others did. They were the first to drop out of Engineering because they couldn’t comprehend the correlations of the math, the physics, or basically the logical cause and effect of nature. Their falling grades forced them to change majors into things like Psychology, Political Science, History, or other “non-exact” disciplines that don’t require as much factual correlation or logic. Some “hard users” dropped out of college altogether. By the end of the Junior year, he was the only Engineering major left of the original eight.
    The second is my own experience... I’m obviously a “light weight.” I tried it when I was 42, just divorced, and looking to rejoin the “social scene.” After a couple of tokes, I was impaired at performing most any critical thinking, or anything that required one to be alert and quick in physical responses. Just zoning out and relaxing was the basic thing to do. I also found that for days later I could not stay focused, reasonably correlate data, or make good decisions in my work. At the time I was heading up 12 R&D projects for United Technologies. The impact on my leadership abilities was very negative. Needless to say, I abandoned marijuana altogether.
    I later found out that the half-life of the active drug in marijuana is 14 DAYS. Compare that to the half-life of alcohol, which is approximately 14 HOURS.
    From my personal observance of multiple colleagues over the past 35 years that used pot, their learning abilities seemed to just plateau... they could not seem to accumulate knowledge, then correlate new experiences or data input and either solve problems or create new ideas based on those correlations. In short, they were noticeably mentally impaired.
    Please consider these experiences and the possible impacts of any recreational drug use if you are faced with peer pressure to indulge.

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