Does marijuana change the brain?

Marijuana doesn’t seem to shrink brains, but the results of a new study suggest the brains of people who use marijuana may be smaller than those who don’t.

Researchers found that marijuana users had some shrinkage in two brain regions called the amygdala and the right ventral striatum, but when they compared marijuana users’ brains to their siblings, the differences disappeared. As a result, researchers believe it’s possible that people who choose to use marijuana may already have the smaller regions in those parts of the brain.

In the study, the brains of 282 twins or siblings between the ages of 25 to 35 years old were analyzed to better understand whether cannabis use was associated with brain volumes. Study leaders included two separate groups of siblings – one who used marijuana and the other who did not – and tried to figure out whether brain differences might be genetic instead of being linked to marijuana use.

Dr. Chandragupta Vedak, a psychiatrist at Advocate Good Shepherd Hospital in Barrington, Ill., provides a different perspective to the theory.

“The endocannabinoid system [a group of lipids and their receptors in the brain] play an important role in the formation of synapses [the connections between neurons], says Dr. Vedak. “This perhaps explains why marijuana may have the strongest long-term impact on young users whose brains are still building new connections and maturing in other ways.”

There still needs to be some conclusive work on marijuana and its effect on the brain, researchers said. Future examination may provide help for substance abuse policy and prevention programs.