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Prolonged marijuana use may affect brain’s pleasure center

Posted on 07-11-2016 Posted in Cognition, Recovery, Research - 0 Comments

Prolonged marijuana use

Consider this image: Two people are racing through the front yard of a mansion, from the mailbox to the front door. A red ribbon marking the finish line is affixed to the threshold of the door.

Arms are pumping, heels kicking back furiously and the two are smiling. But attached to one man is a bungee cord. The uninhibited man crosses the threshold, much to his pleasure, a gratifying reward. The tethered man runs the cord taut and, feeling the resistance, runs in place for a spell before he’s sucked back as it recoils.

According to recent studies, that’s the effect a decade of marijuana dependency has on an individual trying to reach the brain’s threshold for pleasure.

A study of daily marijuana users

For 10 years, Francesca Filbey, Ph.D., and six colleagues used functional connectivity MRIs to analyze the brains of more than 50 marijuana users who partook daily. They also studied close to 70 participants who used marijuana either occasionally or not at all.

Study authors presented different cues to test the mind’s reward response: natural, neutral and cannabis cues.

While the study did not prove causality, researchers found those with decades-long marijuana dependency expressed strong, automatic responses in several parts of the brain for marijuana-related cues.

Nondependent participants did not demonstrate significant response to marijuana or natural cues. In fact, sometimes they displayed more brain activity for the natural cues, which were represented by fruit.

“We found that marijuana disrupts the brain’s natural reward circuitry, making marijuana highly salient to heavy users. … In essence, these brain alterations could be a marker of transition from recreational marijuana use to problematic use,” Filbey said.

The difference between recreational and problematic use, from a user to one dependent on the drug, is significant.

Marijuana and the brain’s threshold for pleasure

“Scientists have found that the brains of pot abusers react less strongly to the chemical dopamine, which is responsible for creating feelings of pleasure and reward.” That is according to an article sponsored by the American Association for the Advancement of Science.

Like the illustration above, a normal brain runs free and is able to enjoy pleasures organically, uninhibited. But a marijuana user who crosses over into dependency is tethered by the addiction. Ironically, although they seek the escapist pleasure of a marijuana high, daily users can no longer adequately reach that sought-after dopamine threshold.

Marijuana and brain changes

Filbey also conducted a 2014 study illuminating brain changes tied to heavy marijuana use. As mentioned previously, it has yet to be determined whether differences predict marijuana dependency or brain alterations developed afterward. Researchers can’t readily scan people’s brains and then ask them to abuse a substance. Nevertheless, Filbey’s previous study illustrated heavy cannabis users:

    • Had a smaller orbitofrontal cortex, the predominant brain area for interpreting emotions and decision-making
    • More cross-brain connections, which researchers surmise are the brain’s way to patch and repair disparities in size
  • Lower IQ scores

Sovereign Health in Florida utilizes brain wellness treatments, cognitive therapies and more to rehabilitating those with mental disorder and substance use issues. Call our 24/7 helpline to learn how we customize treatment to each person.

About the author

Sovereign Health Group staff writer Kristin Currin-Sheehan is a mindful spirit swimming in metaphysical pools with faith as her compass. Her cover: a 30s-something Cinderella breadwinner of an all-sport blended family. Her repertoire includes writing poetry, lifestyle articles and TV news; editing, radio production and on-camera reporting. For more information and other inquiries about this media, contact the author at

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