Cannabis reduces brain in adolescentes?

Daily cannabis use by adolescents and adults is not associated with reduced brain mass

Daily cannabis use is not associated with brain shrinkage when controlling for the effects of alcohol consumption on those who both drink and smoke cannabis, a new study led by neuroscientists at the University of Colorado at Boulder. Dr Kent Hutchison, the senior author of the study, said his team reviewed a number of scientific papers that showed cannabis causes different parts of the brain to shrink, and his team found the studies were not consistent.

“So far, there’s not a lot of evidence to suggest that you have these gross volume changes” in the brain, Hutchison said in an interview with Reuters. In particular, his study examined a publication released last year by researchers at Northwestern University that identified changes to the nucleus accumbens and the nucleus amygdala, regions of the brain that are key to regulating emotion and motivation, in cannabis users who smoke one to seven cannabis cigarettes a week. Hutchison’s team tried to replicate those results by recruiting dozens of adults and adolescents and conducting brain imaging on them, and comparing daily cannabis users to non-users. But he said they took a different approach to rule out the effects of alcohol. “We found no evidence of differences in volumes of the accumbens, amygdala, hippocampus or cerebellum between daily versus non-users, in adults or adolescents,” Hutchison’s paper said.

Weiland BJ, Thayer RE, Depue BE, Sabbineni A, Bryan AD, Hutchison KE. Daily marijuana use is not associated with brain morphometric measures in adolescents or adults. J Neurosci 2015;35(4):1505-12.

Reuters of 4 February 2015