Study: Regular marijuana habit shrinks part of the brain

DALLAS, Nov. 11 (UPI) -- Regular pot smokers have shrunken brains, according to a newly published research out of the Center for BrainHealth at The University of Texas at Dallas.

Scientists there found that study participants who smoked pot at least three times a day had smaller orbitofrontal cortexes (OFC), the portion of the brain known as the "reward center" and one vital to the cognitive processes of decision-making.

That's alarming news for pot smokers, who until recently could take solace in that fact that most research on the health effects of marijuana were all over the map -- and often contradictory in their conclusions. But as pot becomes increasingly popular, now legalized in Oregon, Alaska and Washington, D.C., the latest research suggests a regular pot habit has significant effects on the shape, size and performance of the brain.

"We have seen a steady increase in the incidence of marijuana use since 2007," said Dr. Francesca Filbey, an expert in brain science and addiction, said in a recent press release. "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."

These latest findings -- detailed this week in the Proceedings of the National Academy of Sciences -- did arrive with a bit a qualifier, though. While the MRI scans of showed regular marijuana users had smaller orbitofrontal cortexes, they also displayed a higher level of "connectivity," as if the brain had found a way to compensate for the OFC's diminished size.

This unique adaptation explains why chronic pot smokers "seem to be doing just fine," despite their smaller OFC volumes, Dr. Filbey said. The study found that the benefits of increased connectivity begin to decline after six to eight years of chronic marijuana smoking.

Researchers say the findings are worrisome but inconclusive -- a subject that needs to be explored further. But the findings offer credence to a Harvard study published earlier this year, which found even less regular marijuana use (a few times a week) could have significant effects on the brain's frontal lobe.

"This is a part of the brain that you absolutely never ever want to touch," Hans Breiter, co-author of that study, told Time. "I don't want to say that these are magical parts of the brain -- they are all important. But these are fundamental in terms of what people find pleasurable in the world and assessing that against the bad things."