Teen Brains Damaged by Heavy Marijuana Use

Kathleen Blanchard's picture
Marijuana damages teen brain

A new study suggests that teens and young adults who use marijuana heavily may experience brain abnormalities. According to lead author Manzar Ashtari, Ph.D., director of the Diffusion Image Analysis and Brain Morphometry Laboratory in the Radiology Department of The Children's Hospital of Philadelphia, "Studies of normal brain development reveal critical areas of the brain that develop during late adolescence, and our study shows that heavy cannabis use is associated with damage in those brain regions." (See photo)

Previous studies performed by the research group also used brain imaging to measure adolescent brain development. The current study is an extension of Dr. Ashtari's prior research, and included 14 young men in New York from a residential drug treatment facility. They compared heavy marijuana (6 joints per day in the year they quit), to a control group of 14 matched healthy males. The heavy marijuana users had a history of marijuana use of five to six years, beginning at age 14.


Special MRI's were used, known as diffusion tensor imaging (DTI). Dr. Ashtari says, "The abnormal patterns of water diffusion that we found among the young men with histories of marijuana use suggest damage or an arrest in development of the myelin sheath that surrounds brain cells." When myelin sheath is damaged, brain impulses become slower, affecting memory, attention, language, and decision-making.

Dr. Ashtari says the results are preliminary. The study was small. The researchers also say it is hard to tell which came first – brain abnormalities that lead to heavy marijuana use in the first place, or heavy marijuana use that lead to brain abnormalities. In addition five of the fourteen boys had a history of alcohol abuse.

The study concluded, "Further research should be done to investigate the relation between repeated marijuana use and white matter development. However, our work reinforces the idea that the adolescent brain may be especially vulnerable to risky behaviors such as substance abuse, because of crucial neural development that occurs during those years."

SOURCE: The Children's Hospital of Philadelphia



Wow! Since marijuana is so dangerous why are we following a policy that makes it so readily available to minors? Prohibition doesn't stop teens from smoking marijuana, in fact it makes it much easier for them to be able to buy the stuff than if we treated it like tobacco or alcohol. Licensing reputable businesses to legally produce and sell marijuana to adults will *eliminate* drug dealers from our schools and neighborhoods and dramatically reduce the use of marijuana by teens. So what are we waiting for?
What a terrible article. Nothing is conclusive. People treat marijuana as a deadly substance, well what about all the preservatives in the food we eat? There could be so many explanations for the poor myelin layers.
All of the participants were taken from a drug treatment facility, and 35% of the study participants were alcoholic; How many of them were polydrug users? How many of the particiapants had a history of use of cocaine, opiates, MDMA, or meth? It seems to me that this study needs better controls. If you want to study the effects of Cannabis on the brain, try using people who use marijuana exclusively.
What a terrible article. Nothing is conclusive. People treat marijuana as a deadly substance, well what about all the preservatives in the food we eat?!? Legalize it man, dont criticize it! regulate it just like buying ciggarettes, ID required. it would be such a more civilized enviroment!!!!!!!! no violence or gangs needed! no need to go to a dangerous dark back alley to get this God-given, peace-promoting, HEALING herb!
everything is fine in moderation!!!!! even water can be abused!!!! you drink 2 gallons of water youll die!!!!!!