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By Shamard Charles, MD
Low level of marijuana use ̵
"Most would probably assume that one or two uses (joints) would have no influence, so we were curious to study this – and especially to investigate whether initial uses actually can produce brain changes that affect future behavior as subsequent use, "Hugh Garavan, lead author of the study and a professor of psychiatry at the University of Vermont School of Medicine, said in a mail to NBC News.
The study did not say what the increased brain material meant, but the researchers noted that the gray matter expansion contradicts normal youth development.
"At the age of studying these children (14 years), cortical regions go through a dilution process," he said, suggesting that this is a "sculpture" process that makes the brain and its connections more effective. "One possibility is that cannabis use has disturbed this pruning process, resulting in greater amounts (ie, a disturbance of typical maturation) of cannabis users. Another possibility is that cannabis use has led to growth in neurons and in the connections between them."
It is not the first study to find out that cannabis use can cause changes in teen brain.
A recent study showed that teen brain is more vulnerable to marijuana than alcohol. And in June, the University of Pennsylvania researchers discovered that young people who often used marijuana often were more likely than nonusers to have a slightly lower score on memory testing, learning new information and high-level problem solving and information processing.
According to the latest data published by the National Institute on Drug Abuse, 32.6 percent of the 10th grade reported using marijuana at least once in their lifetime.
So far, 10 states and the District of Columbia have legalized recreational use. Legalization is imminent in several other states, including New York and New Jersey.
Marijuana has shown a great promise of treating medical conditions, including pain, muscle spasms, seizure disorders and cancer chemotherapy nausea. At least some of these benefits are thought to come from cannabidiol, a chemical component of the marijuana plant that is not likely to produce mind-altering effects. However, experts believe that more research is needed to determine how and why the brain is affected by early marijuana use in changing societal attitudes to the drug.
Experts note that these findings are insightful, although it is preliminary.
The expansion of gray matter "does not seem to have a major impact on brain function," said David Nutt, professor of neuropsychopharmacology at Imperial College London, "so even though this study alone is unable to prove that Small amounts of cannabis adversely affect the brain of adolescents, this research area is important and certainly worth studying. "Studies looking at whether alcohol and other psychoactive substances have undesirable brain effects in young people are also worthwhile, he says.
Garavan says the overall pickup is unclear as the study did not investigate major cognitive or mental health differences between users and nonusers. There is also a possibility that larger brains may be a random find so the results have to be confirmed.
"As is the case, more research is needed to replicate these effects, to try to understand the mechanisms and critically, to discover which additional factors can identify which cannabis-using children show these effects and which ones Don't do it, "Garavan said.