Long-term cannabis users may have structural brain abnormalities

Long-term, heavy cannabis use may be associated with structural abnormalities in areas of the brain known as the hippocampus and amygdala, according to a report in the June issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Conflicting evidence exists regarding the long-term effects of cannabis use, according to background information in the article. "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 elucidate the long-term sequelae of long-term cannabis use."

Murat Yücel, Ph.D., M.A.P.S., of ORYGEN Research Centre and the Melbourne Neuropsychiatry Centre at the University of Melbourne, Australia, and colleagues from the University of Wollongong performed high-resolution structural magnetic resonance imaging on 15 men (average age 39.8 years) who smoked more than five joints daily for more than 10 years.

Their results were then compared with images from 16 individuals (average age 36.4) 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.

Source: JAMA and Archives Journals

   

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4.1/5 after 15 votes

• ofidiofile - Jun 02, 2008
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  "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". I'm wondering if the researchers even tried to rule out that smokers may be self-medicating for a pre-existing disorder, i.e., that they are pot smokers BECAUSE of smaller than average amygdalae or hippocampi.
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• nilbud - Jun 03, 2008
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  It's amazing, noone has ever made up such enormously false tales before. Some money must have changed hands. 12% difference in the size of a part of the brain. It's amazing that no research in any credible setting has ever indicated anything like this before. America is truly the land of religion driven invention but it seems those sunburnt antipodeans can make up stuff just as ridiculous.
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• COCO - Jun 03, 2008
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  voodoo science at its best - sense a wee bit of DEA influence on these poor researchers.
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• moebiex - Jun 03, 2008
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  "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".

  I assume smaller implies less anger which suggests to me that cannibis might benefit anger management programs, reduce aggression and who knows- heaven forbid- maybe even provide a quick temperary remedy for things like road rage, family breakup rage and other hard to control emotions. I don't suppose there are any researchers willing to test those though. Maybe they could even quantify recommended dosage(s) as opposed to leaving it as currently accepted "more is better" criteria.
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• Ulg - Oct 02, 2008
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  Schizophrenia is effected directly effected and stimulated from drugs like cocaine and MSG- CB1-CB2 do not activate primarily or secondarily these receptors- eating a bag of cool ranch dorritos or eating a bowl of progresso soup is no doubt worse
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