Pubdate: Wed, 16 Mar 2016
Source: Chicago Tribune (IL)
Copyright: 2016 Chicago Tribune Company
Contact:  http://www.chicagotribune.com/
Details: http://www.mapinc.org/media/82
Author: Dennis Thompson, Health Day

EARLY-AGE POT HABIT MAY ALTER BRAIN, STUDY SAYS

Young teens who smoke pot may wind up with brains that look 
strikingly different from those who start using marijuana later in 
their lives, a new study reports.

Early pot use may alter the physical development of a young teen's 
brain. It seems to obstruct the natural process by which the body 
eliminates unneeded neurons and synaptic connections, the researchers reported.

As a result, the brains of people who started smoking pot younger 
than age 16 tend to have fewer surface wrinkles and folds in the 
outer layer of the brain, also known as the cerebral cortex, said 
study lead author Francesca Filbey. She is chair of behavioral and 
brain sciences at the University of Texas at Dallas Center for Brain Health.

The cortex also tended to be thicker in these early-use teens, again 
suggesting that less development had occurred, the researchers said.

However, the study cannot definitively prove a cause-and-effect 
relationship. Filbey said the researchers couldn't rule out that the 
differences in brain development might drive early marijuana use, 
rather than vice versa.

"It could be that perhaps having these altered brain patterns is what 
led to the greater marijuana use," she said.

Still, the difference in brain development might be due to 
marijuana's influence on dopamine levels in the brain, which could 
influence how the cortex develops, Filbey added.

The research team analyzed MRI scans of 42 heavy marijuana users, 
including 20 considered "early-onset" users because they started 
before age 16. All of the study volunteers began using marijuana 
during their teens and continued throughout adulthood. They all 
reported using pot at least once a week, the researchers said.

The researchers explained that typical brain development for teens 
includes a process called "synaptic pruning." During this process, 
the brain sharpens itself by removing unneeded synapses and neurons. 
The process results in a thinner cortex that contains more wrinkles 
and folds on its surface, as well as greater contrast between the 
brain's gray and white matter.

In this study, the MRIs revealed that early-onset users had thicker 
cortexes, fewer wrinkles and less gray and white matter contrast, 
compared to people who picked up their marijuana habit at 16 or older.

"The difference in association with marijuana use was striking 
between the two groups," Filbey said.

It also appeared that the more marijuana the person used, the more 
their brain development had been affected, the researchers said.

The study was published in the journal Developmental Cognitive Neuroscience.

Dr. Gayatri Devi, a neurologist with Lenox Hill Hospital in New York 
City, pointed out that "these children seem to have less sculpting of 
the brain."

Such alterations to normal brain structure could impact the teens' 
ability to think and reason in later life, said Devi, who was not 
involved with the study. For example, the frontal lobe of the cortex 
often deals with attention, judgment and other higher-level brain function.

"If you don't have the normal sculpting that's seen during this age 
period, then one could speculate those are the areas that would be 
affected," Devi said.

But not everyone is convinced that early marijuana use is responsible 
for these changes.

Mitch Earleywine, a professor of psychology at the State University 
of New York at Albany, also sits on the advisory board of NORML, an 
advocacy group for marijuana legalization. He agreed with Filbey that 
it's not clear if early pot use caused these changes, or that people 
with these brain changes are more likely to start using pot earlier.

"None of these people were randomly assigned to use the plant, so we 
have no way of knowing if the effects actually preceded use or 
stemmed from it," Earleywine said. "I would add that these results 
don't hold a candle to the brain structure changes we see with binge drinking."

Dr. Andrew Adesman is chief of developmental and behavioral 
pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y. 
He said the study results are further warning for parents to keep 
their kids from experimenting with pot at a young age.

"With marijuana being legalized in more states, teens will likely 
perceive it as less risky," Adesman said. "They will also likely have 
greater access to pot in a multitude of forms, including appealing 
foods for consumption. Given these realities, we need to make sure 
that teens also get the message that using pot is not without 
consequences, and it is still not recommended for use by teens."
- ---
MAP posted-by: Jay Bergstrom