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Structural abnormalities in the hippocampus and amygdala may be associated with long-term, heavy cannabis use, according to an article released June 2, 2008 in the Archives of General Psychiatry, one of the JAMA/Archives journals….

The authors continue, quoting statistics regarding cannabis use in the United States: “With nearly 15 million Americans using cannabis in a given month, 3.4 million using cannabis daily for 12 months or more and 2.1 million commencing use every year, there is a clear need to conduct robust investigations that elucidate the long-term sequelae of long-term cannabis use.”

In cannabis users, two major parts of the brain were generally smaller than in their straight counterparts: the hippocampus and the amygdala.

The former is presumed to regulate emotions and memory, and was on average 12% smaller. The latter is related to fear and aggression, and was an average of 7.1% smaller in the users.

Cannabis users also showed more sub-threshold symptoms of psychotic disorders. The authors commented on the verbal learning skills shown by the subjects, but this did not seem to correlate with the brain volume differences in either group.

The authors conclude with a call for more research in this area: “…Although modest use may not lead to significant neurotoxic effects, these results suggest that heavy daily use might indeed be toxic to human brain tissue. Further prospective, longitudinal research is required to determine the degree and mechanisms of long-term cannabis-related harm and the time course of neuronal recovery after abstinence.”

[Regional Brain Abnormalities Associated With Long-term Heavy Cannabis Use, Arch Gen Psychiatry. 2008;65(6):694-701.
Written by Anna Sophia McKenney, Article Date: 02 Jun 2008]