Another study adds to the growing but controversial pile of evidence that heavy marijuana use over the years can lead to changes in the brain. The research, published in Proceedings of the National Academy of Sciences, found that an area in the front of the brain called the orbitofrontal cortex (OFC) is smaller in people who smoke three joints a day than people who never touch the stuff. But what’s interesting about the new study is that it also found greater connectivity in the white matter throughout the brain, suggesting that the brain is trying to compensate in some way – at least for a while. After years of heavy pot use, the study also found, the brain can no longer continue this compensation, and the effects begin to disappear.
The researchers used three different MRI techniques to study the brains of 48 marijuana users and 62 non-users. The pot-smokers averaged three joints per day, which is very heavy use, over about 10 years. They also took cognitive tests, including IQ.