Pubdate: Mon, 25 Mar 2002
Source: Blade, The (OH)
Copyright: 2002 The Blade
Contact:  http://www.toledoblade.com/
Details: http://www.mapinc.org/media/48
Author: Michael Woods
Note: Michael Woods is the Blade's science editor. His column on health 
appears each Monday. Email him at TRUE EFFECTS OF MARIJUANA ARE STILL UNKNOWN

Marijuana shook off its "weed-with-roots-in-hell" reputation decades ago, 
after scientific studies punctured old myths and challenged popular 
misconceptions about the drug.

Folklore about marijuana dates to a classic 1936 film, Reefer Madness: 
Devil 's Harvest. It showed marijuana causing instant addiction, a craving 
for heroin, crime sprees, and insanity.

Newer studies gradually painted a different portrait of marijuana as a drug 
that rarely leads to addiction or serious crime by users. Marijuana found a 
niche in medicine. Although rarely used, it is a second-line drug that can 
relieve nausea and vomiting and certain other problems when other drugs fail.

Millions of Americans have tried marijuana. A 1999 National Academy of 
Sciences (NAS) report estimated that one-third of the U.S. population over 
age 12 - 69 million people - had tried marijuana at least once. Most used 
marijuana for brief periods in their teens or 20s, and stopped.

The growing acceptance of marijuana has fostered a new misconception, 
especially among younger people: That all the scientific uncertainties 
about marijuana's safety have been resolved. Marijuana, they believe, is a 
totally harmless substance persecuted by overly zealous law enforcement 
officials.

In reality, serious scientific questions about marijuana's effects and 
safety remain unanswered.

They extend beyond possible health problems from inhaling marijuana smoke 
into the lungs. As NAS noted, marijuana smoke, like tobacco smoke, contains 
carcinogens and other harmful chemicals.

Inhale smoke containing those substances, and the toxic materials go into 
the blood and circulate throughout the body.

One of the most serious unanswered questions involves marijuana's effects 
on brain cells.

Here's the situation:

Marijuana interferes with the normal workings of brain cells.

That's why marijuana produces its "high" and causes changes in the way a 
user thinks and senses the world.

Computerized brain images of heavy marijuana users show different patterns 
of blood flow and nerve cell activity.

Psychological tests of long-term users also show unusual problems with 
"cognitive functioning." That means problems with memory, focusing 
attention, performing complex tasks, and other problems.

A scientific debate is under way - largely hidden from public view - on the 
importance of those changes. Do brain cells fully recover after a person 
stops using marijuana, with the memory impairments disappearing? Or does 
marijuana have a toxic effect on nerve cells that slowly causes lasting 
damage that worsens after years of use?

Studies in animals reinforce the concerns. They show that marijuana's 
active ingredient alters the activity of a brain system critical for normal 
memory.

Experts agree that cognitive changes last for hours or days after a person 
uses marijuana. But they disagree on whether those problems last longer and 
grow worse over time.

The disagreements are sharp, and one study may reach conclusions exactly 
the opposite of another.

Early in March, for example, an international research group reported that 
cognitive impairments do last and worsen. They studied 102 people who had 
used marijuana almost daily for years.

"The kind of impairments observed in this study have the potential to 
impact academic achievements, occupational proficiency, interpersonal 
relationships, and daily functioning," they reported in the Journal of the 
American Medical Association (JAMA).

Mental impairments, researchers said, develop silently and may be apparent 
only after 10 or 20 years of heavy marijuana use.

A year earlier, equally distinguished researchers found no lasting ill 
effects after studying 108 heavy marijuana users.

"We still must live with uncertainty," Harvard University's Dr. Robert G. 
Pope, Jr., summed up the situation in a JAMA editorial.

Today's marijuana users will do the same - with their own long-term health 
at stake - as unknowing subjects in a huge, real-life experiment. Their 
fate will help scientists paint marijuana's final portrait.
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MAP posted-by: Beth