Teen Brains Damaged by Heavy Marijuana Use
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."