Since before the debates against legalizing marijuana began, there were always claims that the drug can change the brain's structure. Now we have research that has tested many sets of siblings to find where these abnormalities occur, only to find that none of the marijuana smokers had any irregularities compared to their non-smoking siblings after many years.
The researchers hypothesized that in the sibling pairs where one had used marijuana and one had not, they would see differences in brain volume. But instead, they found that the exposed and unexposed siblings had the same amygdala volume. “We found no evidence for the causal influence of cannabis exposure on amygdala volume,” the authors concluded.
Original article: http://time.com/4011265/marijuana-brain-volume/