Pubdate: Wed, 12 Nov 2014
Source: Albuquerque Journal (NM)
Copyright: 2014 Albuquerque Journal
Author: Mike Bush, Journal Staff Writer
Page: A1


UNM Professor Plays a Key Role in the Groundbreaking Research

Longtime, chronic marijuana use causes significant abnormalities in 
brain function and structure - and perhaps lower IQ - according to a 
major new study conducted in part at the Mind Research Network on the 
campus of the University of New Mexico.

Chronic users tend to have a smaller volume of gray matter in a part 
of the brain associated with decision making and addiction and a 
marked increase in a function called brain connectivity, which 
researchers said may be an attempt by the brain to make up for the 
decreased gray matter volume.

The study - the first of its kind and the most significant to date - 
was published Tuesday in the Proceedings of the National Academy of 
Sciences. It was funded by the National Institute of Drug Abuse and 
comes at a time some policymakers in Albuquerque and elsewhere are 
pushing to legalize marijuana use.

Using three different MRI techniques to analyze the subjects, Dr. 
Vince Calhoun, a distinguished research professor of electrical and 
computer engineering at UNM, worked closely with colleagues from the 
Center for BrainHealth at the University of Texas at Dallas. The 
study's lead author was Dr. Francesca Filbey, director of Cognitive 
Neuroscience Research in Addictive Disorders at the Center for 
BrainHealth at UT Dallas. She was formerly with Albuquerque's Mind 
Research Network, where the study began several years ago.

The MRI scans all were taken in Albuquerque, Calhoun said. The 
analysis was completed in Dallas and Albuquerque.

The study clearly shows the effects of longtime marijuana use on the 
brain, said Calhoun, also the executive science officer and director 
of Image Analysis of the MRN, a nonprofit, independent institute 
based on the UNM campus.

What is not known, he said in an interview Tuesday, is whether those 
effects are lasting or if a cessation of marijuana use ultimately 
would mean a return to a more normal brain.

The effects seem to depend to a degree on the age of a user when he 
or she begins smoking pot and how long it is used.

For the project, Filbey, Calhoun and other researchers studied 48 
long-term adult marijuana smokers and 62 gender- and age-matched 
nonusers as a control group. The control group accounted for such 
potential biases as gender, age and ethnicity. The authors also 
controlled for tobacco and alcohol use.

The users who participated in the study consumed the drug three or 
more times a day for an average of 10 years, Calhoun said, adding, 
"That's chronic."

The study found that pot smokers have measurably less volume in the 
orbitofrontal cortex of the brain's frontal lobe, and the evidence 
strongly suggests a relationship with marijuana and the length of 
time the drug was consumed.

The findings indicate gray matter in the front of the brain may be 
more vulnerable than white matter to the effects of THC, the main 
psychoactive ingredient of marijuana.

The MRIs also revealed that youthful and regular marijuana use 
prompts greater structural and functional connectivity in the brain. 
The greatest increases in connectivity appear when someone first 
begins using marijuana, and the more the drug is used, the study 
found, the greater the connectivity.

The increase in connectivity may be a compensatory function of the 
brain to make up for the decrease in volume of the orbitofrontal 
cortex, Calhoun said.

Brain connectivity, which is crucial to processing information, 
refers to connections, dependencies and interactions among various 
and distinct units of the nervous system. Although the increased 
connectivity begins to decline after six to eight years of continued 
use, pot smokers still exhibit more intense connectivity than healthy 
nonusers, a finding that may explain why chronic, long-term users 
"seem to be doing just fine" - despite the smaller brain volumes, Filbey said.

Until now, studies on the longterm effects of marijuana on brain 
structures have been largely inconclusive due to limitations in 
methodologies, she 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," Filbey said.

Cognitive tests showed that the users had slightly lower IQ scores 
compared to the control groups, but the IQ differences are not 
necessarily related to the brain abnormalities. No causative or 
direct correlation was made between IQ deficits and the decrease in 
volume of the affected portion of the brain.

Speaking as a scientist, Calhoun said, he would like to see a 
longitudinal study - one that looks at marijuana users over a 
significant period of time - to see if the structural and cognitive 
changes are permanent.

The study does not address whether consuming marijuana is dangerous. 
Nor would Calhoun give an educated opinion on legalizing pot for 
recreational use or medical marijuana.

"I'll leave that to the policymakers," he said. "That's a very hard 
question to answer."
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