Pubdate: Mon, 18 Jul 2016
Source: Detroit News (MI)
Copyright: 2016 The Detroit News
Author: Evan Carter


A new study put out by University of Michigan researchers suggests 
that over time, marijuana use dampens the response of the area of the 
brain that responds to rewards.

Researchers with UM's Addiction Research Center and Department of 
Psychology found over time marijuana use shifts the brain's reward 
system so that a person may need more of the substance to get that 
level of satisfaction they would normally get from "natural rewards," 
such as food.

"This kind of suggests that marijuana may be biasing the brain's 
reward system away from things the brain would normally find 
pleasurable," said the study's Senior Researcher and UM Assistant 
Professor Mary Heitzeg.

According to Heitzeg, when a person smokes marijuana, THC passes from 
the lungs into the bloodstream, which carries the THC to the brain 
and other organs. In the brain, THC acts on specific brain cell 
receptors that ordinarily react to natural THC-like chemicals. One 
effect of THC in the brain is a release of dopamine from an area of 
the midbrain called the ventral tegmental area to the nucleus 
accumbens, which is a brain structure involved in motivational processes.

The study involved 108 young adults who are at high risk for 
substance use disorder, self-reporting on their marijuana use once a 
year and received 3 MRI brain scans over a 4 year period. According 
to the reports submitted by study participants, some involved did not 
use marijuana, while others used it in light, moderate, or heavy amounts.

Researchers were particularly interested in marijuana's effect on the 
brain's mechanisms underlying addiction, concluding that it may lead 
to the user having problems with addiction later in life.

Rich Birkett, who was an organizer of Ann Arbor's Hash Bash in the 
late-80s and the 90s, disputes that smoking marijuana makes you more 
suseptible to addiction.

"I think the curiosity to try other drugs is largely a social thing: 
what are your friends doing?" Birkett said.

According to Heitzeg, other studies involving marijuana are 
"cross-sectional" and take "snapshot" looks at the affects of use 
versus no use on the brain at one time. Heitzeg said the study she 
helped head up was different because it tracked the affects of 
marijuana use over time, which she hopes makes the study less 
susceptible to be biased by factors other than the drug's affect on 
brain function.

"This is just one piece of evidence that points to the effects of 
substances on the brain and marijuana in particular," she said.

Birkett, who moved to Guadalajara, Mexico from Ann Arbor in 2009, 
said he smokes marijuana for its medical benefits.

"I appear to be younger than I am," he said.

According to the study, there are low perceptions of harm connected 
with marijuana, even though there are documented short-term and 
long-term consequences connected to its use.

Marijuana was approved for limited medical use by the state 
government through a voter referendum in 2008, and the Michigan 
Medical Marihuana Act was amended by the state legislature in 2012. 
Anyone over 18 years old who obtains a medical marijuana license can 
grow up to 12 plants for their own use; licensed caregivers can grow 
for up to 5 patients as well as themselves if they have a medical 
marijuana license.

The group MI Legalize filed a suit against the state in the court of 
claims in June to get their proposal to legalize recreational 
marijuana reinstated on the ballot this November. This week Michigan 
officials asked the court to throw out MI Legalize's suit.

Marijuana is currently still a schedule 1 drug under federal law.

According to the study, marijuana is the most commonly used illicit 
substance in the U.S. and is even more common among young adults. It 
reported that 35 percent of 21- and 22-year-olds said they used the 
drug in 2014.
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MAP posted-by: Jay Bergstrom