A recent study at the Center for BrainHealth at The University of Texas at Dallas has shown that the structure and function of brain area associated with reward, motivation and decision making may be adversely affected by heavy marijuana use. Researchers have used multiple magnetic resonance imaging (MRI) technique to describe existing abnormalities in brain function and structure of long-term marijuana users. Findings show smaller brain volume in the orbitofrontal cortex (OFC) in chronic marijuana user. OFC is a part of the brain commonly associated with addiction. Similarly, Cognitive tests show that chronic marijuana users had lower IQ compared to the control group.
The study also reveals that initial use of marijuana increases structural and functional connectivity. The increase in connectivity depends on severity of the usage of marijuana; more often you use the drug more will be the connectivity. However, the structure and functional connectivity starts to decline after prolonged use of marijuana.
Thus, the increase in connectivity in certain brain areas may be to compensate for the reduced function of some specific brain region. The affect was profoundly observed in people who started to use marijuana very early compared to the ones who started it later in life. The result indicate that young brain is particularly vulnerable to the adverse affects of marijuana.
However, long-term studies are needed to exactly pinpoint marijuana to be responsible for these effects. As it could also be possible that people with lower IQ and smaller OFC might be more likely to turn into heavy marijuana users. Nevertheless the study has added to an increasing number of literature that shows marijuana may be harmful for the brain.