Pubdate: Sun, 12 Jan 2014
Source: Philadelphia Inquirer, The (PA)
Copyright: 2014 Philadelphia Newspapers Inc
Contact:  http://www.philly.com/inquirer/
Details: http://www.mapinc.org/media/340
Author: Ilene Raymond Rush

A NOBRAINER?

More Teens Are Using Marijuana Daily, but Research Shows Regular Use 
May Harm Developing Brains.

Memory loss, cognitive deficits, drops in IQ, and abnormal brain 
structures: these are but a few of the neurotoxic effects that recent 
research has correlated to marijuana use in adolescents.

But while a number of studies suggest a link between these changes 
and regular cannabis use, particularly for young teens, there is no 
definitive evidence that marijuana is entirely to blame. Adolescents 
who smoke daily, for example, may have problems that predate marijuana use.

One thing is certain: pot smoking among American teenagers is on the 
rise. According to the 2013 Monitoring the Future survey from the 
National Institute on Drug Abuse, 6.5 percent of high school seniors 
smoke daily, up from 2.4 percent in 1993.

And with a recent Gallup poll finding that 58 percent of the American 
public favors legalization - and with marijuana already legal in 
Washington state and Colorado - understanding any negative effects of 
marijuana has gained fresh urgency.

"This is really hard research to do," admits Sharon Levy, medical 
director of the Adolescent Substance Abuse Program at Boston 
Children's Hospital. "We can look at big groups of kids that decided 
to smoke and look at their outcomes, but that data can only show us 
associations. But this was how we did tobacco research and discovered 
problems with nicotine.

"It's always hard to study something that is an illegal behavior - 
we're never going to do a study where we take 100 14-year-olds and 
ask half of them to smoke marijuana," Levy said. "Our advantage today 
is that we can look at the brain, and we have a more sophisticated 
sense of neurobiology." "As the rates of smokers go up," she added, 
"more and more studies will show findings pointing in the same 
direction. More and more, we will come to say that this is not just 
an association."

Thomas McLellan, CEO of the Treatment Research Institute in 
Philadelphia and a former high-ranking drug adviser to the Obama 
administration, agrees with Levy.

"There are known problems with marijuana. It's a fact that as use of 
marijuana becomes more regular and done by a person who has a 
developing brain, you have concentration, motivation, and cognitive 
problems associated with the drug," McLellan said. "The effects vary 
with dose, duration, and population. If you have a smart, capable, 
older adolescent smoking every once in a while, there may be a very 
minimal effect. But for 14-year-olds who have underlying problems of 
depression and concentration, you have a much more serious problem. 
How significant and how pervasive isn't clear, but they exist.

"You can be a proponent of marijuana or you can be against 
marijuana," he said, "but you can't say marijuana is good for a 
developing brain."

A number of new studies support that. In research in the journal 
Schizophrenia Bulletin, healthy and schizophrenic teens who smoked 
cannabis daily for three years, then abstained for two years, showed 
abnormal brain structures on MRIs and had declines in memory when 
compared with nonsmokers.

Memory-related structures in the brains of adolescent smokers 
appeared to shrink and collapse inward, perhaps reflecting a decrease 
in neurons. The younger the smokers were when they started using 
marijuana, the greater the abnormalities.

"We observed a lower level of performance in the marijuana groups 
that was associated with the pattern of how the brain looked," said 
lead author Matthew Smith, assistant research professor of psychiatry 
at Northwestern University.

While documenting these abnormal MRIs in heavy marijuana smokers, 
Smith warned that the study provided a picture "at one point of time" 
rather than over a long period. So he could not say definitively that 
marijuana alone caused the changes.

"One thing we can be sure of is that marijuana has a stronger effect 
on younger brains," Smith said. "At that age, the brain is changing 
on a daily basis, and it's risky to introduce substances into the 
brain that have detrimental effects. And if someone has a family 
history of schizophrenia, data shows that there could be an increased 
risk for developing that disorder if someone uses marijuana."

Smoking marijuana regularly before age 18 "has been linked with the 
greatest neurocognitive deficits," according to a recent study in 
Frontiers in Psychiatry. The study notes that cannabis has been tied 
to structural abnormalities in brain areas that underlie "inhibitory 
control, working memory and attention, emotional regulation, and 
processing speed in teenagers 15-19, all of which translate into 
poorer cognitive functioning," said lead author Krista Lisdahl, 
assistant professor of psychology at the University of Wisconsin-Milwaukee.

"There is substantial resistance to the idea that regular marijuana 
use is detrimental to health," Lisdahl said. "I can see why this gets 
confusing. For example, demonstrating that part of the marijuana 
plant ( e. g. THC) significantly improves nausea in a clinical trial 
over a limited time period in individuals with life-threatening 
conditions does not mean that marijuana is good for your health."

"Most teens and young adults care about their brain and physical 
health," Lisdahl continued. "Marijuana has several psychoactive 
ingredients, especially THC, that attach to cannabinoid receptors 
throughout the brain. Over time, if you keep using regularly, you 
will begin to change your brain structure and how the brain connects. 
You will likely experience symptoms of craving and other cognitive 
and emotional symptoms."

Another study, from Duke University in PNAS, linked persistent 
cannabis use to neuropsychological decline from adolescence to 
midlife, as measured by lower IQs among 1,000 New Zealanders. 
Subjects who smoked marijuana in adolescence and continued to use it 
for years afterward showed a drop in IQ of eight points between ages 
13 and 38. Quitting pot did not appear to reverse the loss, said lead 
researcher Madeline Meier, now an assistant professor of psychology 
at Arizona State University.

Meier's findings were challenged by economist Ole Rogeberg, senior 
research fellow at the Frisch Centre in Norway, who blamed 
socioeconomic factors for the reported drops in IQ. In a response in 
PNAS, Meier discounted Rogeberg's objections, but also noted, 
"Observational studies like ours cannot prove causation."

There is much less debate about the wisdom of adolescents using 
marijuana. Colorado, which began allowing limited retail sales of 
marijuana on Jan. 1, forbids use by anyone under 21.

"Young people should not be using marijuana, alcohol, or any other 
illegal drugs," said Mason Tvert, director of communications for the 
Marijuana Policy Project, a pro-legalization group.

He also maintained that "marijuana causes far less harm than 
alcohol." So what's a parent to do? "These are things I know," said 
Gary Emmett, clinical professor of pediatrics at Thomas Jefferson 
University Hospital. "That when smoked by a mother, marijuana is 
transferred to the fetus. That when a mother is breastfeeding, the 
marijuana gets to the baby in large amounts. My gut feeling is that 
marijuana is bad for infants and children."

When it comes to adolescents, those who self-medicate with alcohol or 
drugs may already have problems, Emmett said. "People who use 
substances get in a lot more trouble, they have poorer academic 
achievements, and often have preexisting reasons which prompt them to 
use drugs."

Yet, this doesn't detract from the drug's effects, which can include 
poor school performance and reckless driving, he added.

Levy, who views marijuana as an addictive drug, worries about the 
effects of secondhand smoke on children and toddlers who might ingest 
marijuana. She also warned that public-health authorities and parents 
are behind in talking about marijuana to children and teens.

"More and more people believe that marijuana is entirely benign and 
don't know what to think about or do about their kids using 
marijuana," she said. "Ten years ago, a kid who smoked would be 
brought in to a substance-abuse center right away, but now there is 
so much information out there saying that marijuana is really benign."

"I was recently in a New York City subway car and noticed all the 
messaging against sugar sweetened beverages," Levy said. "I know 
parents who won't let their kids have a Coca-Cola but don't know what 
to do about marijuana."

In the end, Lisdahl offers this advice: "Do not try marijuana under 
age 18. If you have used marijuana, make sure that you use it less 
than once a month.

"Life is challenging and you want every advantage you can get."
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MAP posted-by: Jay Bergstrom