DISTRICT OF COLUMBIA: Using marijuana does not cause changes in brain volume, a new study suggests.
Public health experts have cited concerns that using marijuana could be associated with structural changes in the brain. However, a new trial comparing the brains of marijuana users and non-users to their siblings reveals that marijuana use likely does not cause changes in brain volume.
In the study, published in the journal JAMA Psychiatry, researchers looked at a large group of siblings ages 22 to 35. Of the 483 people, 262 reported ever using marijuana, even just once. The researchers then split the men and women into groups: sibling pairs who had never used marijuana, sibling pairs where both had reported using marijuana, and sibling pairs where one had used marijuana and one had not. Overall, they noticed that people who reported using marijuana had smaller volumes in certain parts of the brain—like the left amygdala, which is involved in emotional processing. However, these differences still fell within a range of volume that is considered normal.