Marijuana affects cannabinoid receptors which are found in brain regions that influence learning, memory, appetite, coordination, and pleasure. Affecting those receptors is how marijuana use produces the effects it has on users. What researchers do not fully understand is what effect that marijuana can have on the brain when someone uses the drug regularly over a long period of time. Neuroimaging studies show that there are differences between the brains of marijuana users and non-users.
Impaired Neural Connectivity
According to the National Institute on Drug Abuse, some of what scientists do not know is what the differences seen on the MRI images mean and how long the difference last if someone quits using marijuana. MRI image studies of teen brains show that those who regularly use marijuana display impaired neural connectivity in specific brain regions involved in a broad range of executive functions like memory, learning, and impulse control compared to non-users. One question this raises is to what degree this may reflect pre-existing differences that might lead to increased substance use and further changes in the brain.
Loss of I.Q. Points
A large, longitudinal study in New Zealand found that frequent marijuana use by adolescents was linked to up to a loss of 8 IQ points in mid-adulthood. That same study also found that teens who persistently used marijuana in adolescence but quit using still had a decline in IQ as adults.
Largest Effect on Young Brains
Researchers believe that marijuana’s strongest long-term effects occur with young smokers whose brains are still developing neural connections. Research into the effects of marijuana on the brain has been hampered by the fact that most people who use marijuana also drink alcohol, or other substances, which can have their own negative effects on the brain.
