Cannabis’s Long Term Effects on the Brain

For the first time, researchers have described existing abnormalities in brain function and structure of long-term Cannabis consumers via use of multiple magnetic resonance imaging (MRI) techniques. The studies show that chronic marijuana users have smaller brain volume in the orbitofrontal frontal cortex, a part of the brain commonly associated with addiction. However, and a big finding at that, the study also revealed increased brain connectivity in such users.

The research team studied 48 adult marijuana users and 62 gender- and age-matched non-users. The authors also controlled for tobacco and alcohol use. On average, the marijuana users who participated in the study consumed pot three times per day. Cognitive tests did indeed show that chronic marijuana consumers have lower IQ compared to age- and gender-matched controls; however, the differences do not seem to be related to the brain abnormalities as no direct correlation can be drawn between IQ deficits and orbitofrontal cortex volume decrease! According to Dr. Sina Asian, founder and president of Advance MRI, LLC, “The results suggest increases in connectivity, both structural and functional that may be compensating for grey matter losses. Eventually, however, the structural connectivity or ‘wiring’ of the brain starts degrading with prolonged marijuana use.”

Nevertheless, tests reveal that earlier onset of regular marijuana use induces greater structural and functional connectivity. The greatest increases in brain connectivity appear as an individual begins using marijuana. Findings show severity of use is directly correlated to greater connectivity. Although increased structural wiring declines after six to eight years of chronic use, Cannabis consumers continue to display more intense connectivity than healthy non-users, which may explain why chronic, long-term users “seem to be doing just fine” despite smaller orbitofrontal brain volumes.