Habitual Marijuana Use May Increase Brain Abnormalities

Brett Smith for redOrbit.com – Your Universe Online

Oregon and the District of Columbia recently voted to legalize the recreational use of marijuana, buoyed by advocates’ claims that the drug is no more harmful than alcohol.

While that may or may not be true, a new study published in Proceedings of the National Academy of Sciences has found a connection between long-term marijuana use and brain abnormalities.

Using magnetic resonance imaging (MRI) technology, the study team saw that chronic pot smokers have a smaller orbitofrontal cortex (OFC), a part of the brain linked to addiction. Interestingly, the study team also saw increased brain connectivity in long-term users.

“We have seen a steady increase in the incidence of marijuana use since 2007,” said Francesca Filbey, an associate professor of brain sciences at The University of Texas at Dallas. “However, research on its long-term effects remains scarce despite the changes in legislation surrounding marijuana and the continuing conversation surrounding this relevant public health topic.”

In the study, scientists examined 48 adult marijuana users and 62 non-users in the same age, ethnic and gender groups, which took into consideration likely biases. The study team also considered participants’ tobacco and alcohol use.

The researchers saw that participants who used did so three times daily. Cognitive tests revealed that chronic marijuana users had reduced IQ as opposed to the control group. However, the IQ inconsistencies do not appear to be linked to the brain irregularities as no direct relationship can be drawn between IQ deficiencies and lower than normal OFC volume.

“What’s unique about this work is that it combines three different MRI techniques to evaluate different brain characteristics,” said study author Sina Aslan, an adjunct assistant professor of neuroscience at The University of Texas at Dallas. “The results suggest increases in connectivity, both structural and functional that may be compensating for gray matter losses. Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use.”

Assessments also showed that previous onset of habitual marijuana use induces higher physical and functional connectedness within the brain. Greatest rises in connectivity arose as an individual starts using marijuana. Data show seriousness of use is directly linked to greater connectivity, the researchers said.

While higher physical wiring drops off after six to eight years of extended chronic use, marijuana users continue to keep showing stronger connectivity than healthy non-users, which might clarify why chronic, long-term users “seem to be doing just fine” in spite of smaller OFC brain volumes, Filbey speculated.

“To date, existing studies on the long-term effects of marijuana on brain structures have been largely inconclusive due to limitations in methodologies,” Filbey said. “While our study does not conclusively address whether any or all of the brain changes are a direct consequence of marijuana use, these effects do suggest that these changes are related to age of onset and duration of use.”

The study authors said their evidence indicates long-term marijuana use sets off a complex process that allows neurons to evolve as gray matter decreases, but further reports are needed to figure out if these effects end if marijuana use stops, if comparable effects can be found in occasional marijuana users as opposed to chronic users and if these effects truly are a direct result of pot use or simply due to a predisposing factor.

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