Some might say that marijuana is not a dangerous drug overall.

But new research released today suggests that it can have a profound negative impact on the development of the adolescent brain, and maybe even predispose one to schizophrenia.

With the drinking age at 21, many teens turn to marijuana as a way to get high. And many would argue, that given the two evils, marijuana is a lesser one. That can be debated at length, but consider the new research which shows that adolescents who are heavy pot smokers have visual changes on their brain scans--showing diminished development in key areas, which are important for higher level thinking.

Dr. Sanjeev Kumra, a researcher at Long Island Jewish Medical Center, says, “This is a fiber involved in language development that this is an area where there is growth and developing in late adolescence. They are becoming stronger as people get older.”

Actually, those areas are supposed to be getting stronger.

“During adolescents a number of different cognitive functions are continuing to grow and improve.We know the type of essay you can write at grade 9 is very different than the type of essay you can write in college. There must be parts of the brain that are growing that allow you to be able to think more in abstract terms to be able to use inferential thinking,” says Dr. Kumra.

But with heavy pot smoking, there’s now visual evidence this and other key parts of the brain may very well be damaged—perhaps permanently.

Research presented at the Radiological Society of North America’s Annual Meeting shows that heavy use of marijuana may be putting adolescents at risk for delayed development of an important area of the brain--in the language area.

It’s here--in the region of the arcuate fasiculus--fasiculus referring simply a bundle of nerve fibers which is now seen to be affected significantly by pot smoking.

The researchers compared the brains of non pot smoking kids to heavy smokers. They actually created an average brain of each group using a technique called diffusion tensor imaging.

“And then we subtract those two images to see where the brains are different. And that’s where we end up with these sort of orange blobs which tell us what these forebrains regions are different in those who smoke cannabis compared to the healthy individuals who don’t smoke cannabis,” says Dr. Kumra.

The researchers found the abnormalities were the same as those found in schizophrenics.

And when they looked at schizophrenics who smoked pot, the abnormalities were even more pronounced.

So in addition to interfering with normal brain development, heavy marijuana use in adolescents may also lead to an earlier onset of schizophrenia in those predisposed to the disorder.

“People who think that marijuana a is a safe drug or a benign drug, we have evidence that that may not be true and even more so for the adolescents who are at risk for schizophrenia. This may be a very dangerous drug for them to be using,” Dr. Kumra argues.

Marijuana is the most widely used illegal drug. Over 25 million individuals used it in 2003. Around 17 to 22 percent of high school students smoke pot at least on a monthly basis.

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