14 DAY TRIAL // The parts of the brain affected by long-term, heavy cannabis use are those where memory and the regulation of emotion functions reside. High resolution magnetic resonance imaging of the brain of 15 men who have been smoking at least five joints per day for periods of time at least 10 years long compared to that of people who haven't been consuming any drugs show that the hippocampus region of the brain of cannabis users has suffered a decrease in volume of about 12 percent, while the amygdala, responsible for controlling fear and aggression decreased by 7.1 percent.
The study was conducted by Murat Yucel from the University of Melbourne. The results have a high degree of accuracy since the tested people haven't consumed any other drugs more than 10 times in their lives, but have been drinking moderate amounts of alcohol. Also, the study shows that both long and short term memory has been altered in heavy cannabis users.
"They are only about 39, but they were performing at the level of a 55- or 60-year-old", Yucel said.
Heavy cannabis consumers are also more likely to suffer from paranoia and social withdrawal, while the decrease in the volume of the hippocampus is highly likely to trigger psychotic disorders, even though the tested patients didn't show any symptoms of such afflictions. The volume decrease in the mentioned areas of the brain appears to be directly related to the consumed amount of cannabis, meaning that the drug is most likely responsible for the shrinking.
Other similar studies had previously found that cannabis did not affect the brain in any way, probably because they used as test subjects people who consumed moderate amounts of cannabis and the brain scanning techniques were not all that accurate as the high-resolution magnetic resonance imaging used in the investigation carried out by Yucel.