Heavy Pot Smoking May Cause Structural Brain Damage

New research being published in the June issue of Archives of General Psychiatry, one of the JAMA publications, shows that ong-term, heavy cannabis use may be associated with structural abnormalities in areas of the brain known as the hippocampus and amygdala.

There has long been conflicting evidence regarding the long-term effects of cannabis use. The authors write, “Although growing literature suggests that long-term cannabis use is associated with a wide range of adverse health consequences, many people in the community, as well as cannabis users themselves, believe that cannabis is relatively harmless and should be legally available,” the authors write.

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 clarify the long-term effect of cannabis use.

The research was conducted by Murat Yücel, Ph.D. and his colleagues at the University of Melbourne, Australia, along with those from the University of Wollongong. They performed high-resolution structural magnetic resonance imaging on men who smoked more than five joints daily for more than 10 years. Their results were then compared with images from individuals who were not cannabis users. All participants also took a verbal memory test and were assessed for subthreshold (below the standard of disease diagnosis) symptoms of psychotic disorders, which include schizophrenia and mania.

The hippocampus, thought to regulate emotion and memory, and the amygdala, involved with fear and aggression, tended to be smaller in cannabis users than in controls (volume was reduced by an average of 12 percent in the hippocampus and 7.1 percent in the amygdala). Cannabis use also was associated with sub-threshold symptoms of psychotic disorders. “Although cannabis users performed significantly worse than controls on verbal learning, this did not correlate with regional brain volumes in either group,” the authors write.

There is ongoing controversy concerning the long-term effects of cannabis on the brain. These new findings challenge the widespread perception of cannabis as having limited effect on the health. 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. It's clear to me that those who seek a daily "buzz" need to reconsider the effect this habit is having on their body and mind.

Dave