Marijuana Study: Chronic Users Have Smaller, More Connected Brains

According to a new study, chronic marijuana use, especially from a young age, can decrease the size of the brain and reduce IQ scores, and the brain will increase connectivity as a means to compensate. The researchers were careful to point out that their study is not conclusive proof that marijuana use harms the mind, but it might have implications for brain development with further research.

In a test of 48 marijuana users and 62 nonusers, researchers at the School of Behavioral and Brain Sciences in the University of Texas at Dallas found that participants who started smoking at the age of 14 had less brain volume in the orbitofrontal cortex. They made that conclusion using MRI scanners on the subjects. According to CNN, the orbitofrontal cortex is the part of the mind that helps with making decisions.

The main investigator, Dr. Francesca Filbey, explained that the younger the person is when they start using, the more pronounced the effects.

As CBS News explained, the marijuana also seemed to lead to more connections between cells.

Filbey explained the connectivity as a compensating measure.

“The changes in connectivity may be considered a way of compensating for the reduction in volume. This may explain why chronic users appear to be doing fine, even though an important region of their brain is smaller in terms of volume.”

Naturally, the study has some staunch critics who say it isn’t useful, like Paul Armentano, the deputy director National Organization for the Reform of Marijuana Laws.

“Investigators in this study failed to assess whether any of these differences are positively associated with any measurable adverse performance outcomes, such as cognitive [mental] performance or quality of life.”

The researchers did measure IQ scores, which were on average five points lower for users than for nonusers. However, the study did not attempt to control for other factors that may have contributed to a decrease in IQ.

As previously reported by the Inquisitr, Krista Lisdahl of the University of Wisconsin-Milwaukee also said that marijuana can reduce IQ scores, along with memory and cognition citing a different from the PNAS.

Still, for the Filbey’s study, the researchers themselves were quick to point out the limitations to their findings.

“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 full study on marijuana’s effect on the brain can be found here.

[Image Credit: Wikimedia Commons]