marijuana-studyDespite the growing widespread acceptance of marijuana use in the United States, much is still unknown about the long term effects the drug has on the brain. A research team from the Center for BrainHealth at The University of Texas at Dallas has found that the effects of chronic marijuana use on the brain may depend on the age of first use and duration of use, according to Science Daily.

Between the growing medical marijuana movement and subsequent legalization in four states, more people are using marijuana. Many believe that a legalization measure will pass in California in 2016, which could tip the scales for the movement, due to the state’s large population. It is clear that more research is needed before any solid conclusions regarding the dangers of long term marijuana use can be reached, especially now that more states are proposing measures to legalize the drug for recreational use.

“We have seen a steady increase in the incidence of marijuana use since 2007,” said Dr. Francesca Filbey, Director of the Cognitive Neuroscience Research in Addictive Disorders at the Center for BrainHealth and Associate Professor in the School of Behavioral and 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.”

Researchers conducted MRI’s and cognitive tests on 48 marijuana users that smoked, on average, three times a day, the findings showed that chronic marijuana users had lower IQ’s and smaller brain volume in the orbitofrontal cortex (OFC), a part of the brain commonly associated with addiction. However, the lower IQ scores did not seem to be related to the brain OFC volume decrease.

“To date, existing studies on the long-term effects of marijuana on brain structures have been largely inconclusive due to limitations in methodologies,” said Dr. Filbey. “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 findings are published in Proceedings of the National Academy of Sciences (PNAS).