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In a study published in December 2013, researchers at Northwestern Medicine discovered that the developing teenage brain may be particularly vulnerable to excessive marijuana use. The researchers found that teens who smoked marijuana daily for about three years had abnormal changes in their brain structures related to working memory and performed poorly on memory tasks.
In an alarming twist, the study found abnormalities in brain structure and also identified memory problems two years after the heavy marijuana users had stopped smoking pot as teenagers. The researchers found that memory-related structures in their brains appeared to shrink and collapse inward, reflecting a possible decrease in neuron volume. These findings indicate that there could be long-term detriments of chronic marijuana use as a teenage.
Cannabis use has long been associated with working memory impairments. However, the exact relationship between cannabis use and working memory neural circuitry remains somewhat of a mystery.
Previous research has found that prolonged cannabis use is detrimental to mental health. This Northwestern study is the first to target key brain regions in the deep subcortical gray matter of heavy marijuana smokers using structural MRI and to correlate abnormalities in these regions with working memory.
The Northwestern team examined whether a cannabis use disorder (CUD) was associated with differences in brain structure between control subjects with and without a CUD. The study reports that the younger the individuals were when they started chronically using marijuana, the more abnormally their brain regions were structured. The findings suggest that the brain regions related to memory may be more susceptible to the effects of cannabis if abuse starts at an earlier age.