WHAT DOES MARIJUANA DO TO THE GROWING BRAIN?

An Allstate Insurance advertisement suggests that teenagers are
missing part of their brain.

And while any parent can probably say that is true, Great Falls
neurological surgeon Paul Gorsuch said there is scientific evidence
that shows that your brain is not fully developed until you are in
your early 20s, usually around age 23.

"While the overall size of the brain does not change much during
adolescence, relative amounts of different components, nerve
connections, nerve growth, and brain chemical transmitters are all
maturing," Gorsuch said.

The frontal cortex of the brain is where all these changes are
happening. It's the last brain region to fully develop. This
scientific evidence explains a lot about teenager's behaviors,
because the frontal cortex is responsible for executive functions
including logic, decision making, abstract reasoning, evaluating
options, weighing probabilities and determining risks.

If you change the development of your frontal lobes, it is likely
those abilities you have will be diminished from what you might have
been, but much has gone unproven, explained Gorsuch.

When a person smokes marijuana, the chemical binds to special
cannabanoid receptors, many of which are in the frontal cortex of the
brain.

When the drug locks to the receptor, it creates a series of complex
reactions.

"Any chemical that has an effect on our brain -- sugar, narcotics,
nicotine, the cannabinoids in marijuana, adrenaline -- create that
effect by binding or docking to a receptor," Gorsuch said. "In the
case of narcotics, one of the ultimate results is that we may 'feel'
less pain."

Cannabanoid receptors are present in the body at only 14 days
gestation, which means they are crucial for telling nerves where to
go, what to make, what to do and what to connect to, Gorsuch said.

"Basic science says that these are important in how the brain
develops," he said.

Here is where the debate begins.

Scientists do not understand the role of cannabanoid receptors in the
development of the frontal cortex connections.

"So what happens when you start stimulating those cannabanoids (with
marijuana) more than usual? In terms of what it is doing at a
molecular level, we don't know," Gorsuch said.

Gorsuch said scientists do not fully understand how the process is
occurring, but "there are likely 'critical windows' of development
when artificially stimulating potent chemical receptors in the brain
may result in permanent brain changes."

"It's a big black box," he added.

Many studies have been done, but the evidence is still not
scientific.

"All the evidence is showing a trend, but we don't know for sure,"
Gorsuch said. "You can say that there is evidence to not do it."

Dr. John Stowers, who is an emergency room doctor in Great Falls,
also prescribes medical marijuana to those patients he thinks the
benefits outweigh the risks. For teens, he said, it would be rare for
it to be worth the risks.

"Chronic, habitual use at a young age delays maturity both mentally
and socially," Stowers said.

Since the early 1990s, functional MRIs have also clued scientists in
to what happens to a brain on marijuana. One study compared two
different adolescent groups -- one group did not use marijuana and
the other group were chronic marijuana users who stopped for one
month prior to testing.

"While the marijuana group could complete the tasks assigned, their
overall thinking abilities were worse and the functional MRI showed
that they had to use more of the parietal and frontal lobes of their
brains to accomplish the same task the non-users did with less of
their brain," Gorsuch said.

"Or, as the author of the study put it, speaking of the marijuana
users, 'Their brain is working harder that is should,'" Gorsuch added.

Gorsuch also believes that addiction is "an adolescent
risk."

He said teens are probably much more venerable of becoming addicted
than someone who makes it into their 20s or 30s without becoming
addicted to a substance.

"It's a much bigger risk," he said.

Some will argue that only those who are prone to addiction will
become addicted.

"It's a simplistic view to say that," he said.

It comes back to nature versus nurture, and Gorsuch said it's more
complicated than just one or the other. It's a mixture of
probabilities.

What is known for sure is that for those genetically predisposed to
schizophrenia run a much higher risk of developing the disease if
they smoke marijuana as an adolescent.

"One study has said that you are more than six times more likely if
you smoke it more than 50 times," Gorsuch said.

Other studies suggest that the risk is there even if it doesn't run
in your family.

"Literature suggests there could be a potential factor on its own,"
Stowers said.

But the nature of the association between long-term marijuana users
and an increase in psychotic illnesses has yet to be proven, Gorsuch
added.

Stowers said he is careful not to prescribe medical marijuana for
anyone with a major psychiatric history.

He said the mental health community in general do not like using
marijuana as a medicine, because "the benefits don't outweigh the
risks."