Wednesday, 27 August 2014



A study by Harvard Scientists has discovered that the size and shape of two brain regions involved in emotion and motivation ( nucleus accumbens and the amygdala ) may differ in young adults who smoke marijuana at least once a week. According to their study published  in The Journal of Neuroscience on April 16th 2014 their findings suggest that recreational  use of marijuana may lead to previously unidentified brain changes, and highlight the need for further research into understanding the long-term effects of low to moderate marijuana use on the brain.

Marijuana is the most commonly used illicit drug in the United States, with an estimated 18.9 million people reporting recent use, according to the most current analysis of the National Survey on Drug Use and Mental Health. Marijuana use is often associated with motivation, attention, learning, and memory impairments. Previous studies exposing animals to tetrahydrocannabinol (THC) — the main psychoactive component of marijuana — show that repeated exposure to the drug causes structural changes in brain regions involved with these functions. However, less is known about how low to moderate marijuana use affects brain structure in people, particularly in the age group studied.

Jodi Gilman, PhD, Anne Blood, PhD, and Hans Breiter, MD, of Northwestern University and Harvard Medical School used  (MRI) scans to compare the brains of 18- to 25-year olds who had reported smoking marijuana at least once a week with those with little marijuana use. Psychiatric evaluations ruled out the any possibility that the  users were dependent on the drug, the data did  show that they all had significant brain changes. The nucleus accumbens — a brain region  involved in reward processing — was larger and altered in its shape and structure in the marijuana users compared to non-users.

Co -author Anne Blood  said,"There is this general perspective out there that using marijuana recreationally is not a problem — that it is a safe drug.We are seeing that this is not the case."

Another co-author Hans Breiter said,"We looked specifically at people who have no adverse impacts from marijuana — no problems with work, school, the law, relationships, no addiction issues."

Using three different  techniques, they then looked at the nucleus accumbens and the amygdala of the people studied. These areas are responsible for gauging the benefit or loss of doing certain things, and providing feelings of reward for pleasurable activities such as food, sex and social interactions.

 Breiter said, "This is a part of the brain that you absolutely never ever want to touch, I don't want to say that these are magical parts of the brain — they are all important. But these are fundamental in terms of what people find pleasurable in the world and assessing that against the bad things."

Surprisingly, every  person in the test group, had noticeable abnormalities, with the nucleus accumbens and the amygdala showing changes in density, volume and shape. Those who smoked more had more significant changes in these areas.

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