Marijuana can change brain structure, but does not shrink the brain, studies suggest
Two new studies in the Journal of the American Medical Association’s JAMA Psychiatry assessed brain size and risk of developing schizophrenia among marijuana users. Although these studies don’t paint a clear picture of how exactly cannabis use affects the brain, as stated by Dr. David Goldman of the National Institute on Alcohol Abuse and Alcoholism, the researches covers an previously unexplored area of marijuana possible effects.
In the first study, scientists used MRI brain scanning to compare brain sizes of 482 siblings, one who used marijuana and other who didn’t, to asses whether siblings’ brain differences are genetic or connected to cannabis. Even though marijuana users were found to have slight shrinkages in the amygdala and the right ventral striatum of the brain, when to their non-using siblings, the differences disappeared. The scientists advanced the theory that people with smaller brain regions may have a bigger tendency to use cannabis, but that yet remains unsure.
The significant difference, instead, not linked to the MRI tests though, was that marijuana users “tended to be poorer, less agreeable, more likely to use other drugs, and more likely to discount larger future rewards for the immediacy of smaller ones”, according to Dr. Goldman.
THC found in the cannabis is a psychoactive drug that affects the function of the brain. Psychoactive drugs “alter the connectivity of regions of the brain. And they alter the function of particular neurons and circuits”, Dr. Goldman adds. Dr. Goldman also expressed his worries about loose restrictions on marijuana in certain states, because medical specialists do not yet know too much about its effects. “These new studies show that some effects of cannabis use on brain volumes, although a big concern, are probably innate, rather than due to the drug exposure. However, there are many other effects of cannabis to be concerned with, including effects on the neurocircuit that can be seen in other ways,” he said.
On the other hand, other previous studies have found abnormalities in users brains and have strongly suggested that cannabis affects brain structure and development, especially in teens. In 2013, a study found that the brain of heavy users had altered sub-cortical regions who affect memory and cognitive processes.
In the second study, Dr. Tomáš Paus of the Rotman Research Institute in Toronto and his team of researchers assessed as many as 1.500 high genetic risk of schizophrenia teenagers, both marijuana users and non-users. The users were found to have thinner brain cortices: “Our findings suggest that cannabis use might interfere with the maturation of the cerebral cortex in male adolescents at high risk for schizophrenia,” scientist noted. Also, researchers suggested that some people can be more susceptible than others when it comes to cannabis effects on their brain.