Drug study links memory to weed


Results of a study focusing on the effects of marijuana use on the brain found that the areas of the brain that control memory and emotion also drive the reward network that triggers the intense desire to seek out the drug.

Francesca Filbey, associate professor and researcher at the Center for BrainHealth, took part in a $500,000 grant used to fund a consortium of four universities to study the effects of marijuana in dependent and non-dependent users.

“Marijuana has been around for a long time and it has been used for a variety of purposes, we actually know very little about the long term effects on the brain,” Filbey said in an interview in May. “That is an important absence of information in the scientific literature that I thought was important to fill.”

Her study focused on users’ reactions to paraphernalia. Subjects observed and touched cannabis-related cues such as a pipe used for smoking. At the same time, subjects were put through a brain scan while Filbey and her colleagues looked at how reward areas of the brain reacted.

Filbey said that one surprising outcome of the study was not finding any major differences in overall regional brain activity.

“While we expected that the network connectivity would differ with severity, we predicted that some regional activation would also distinguish the two groups of users,” Filbey said.

However, while overall regions of the brain did not differentiate in activation, the network that connected these regions did vary.

Doctoral student and research assistant Sam Dewitt works with Filbey at the Center for BrainHealth on various related projects.

He explained that the functional connectivity, or the network connecting the reward regions to the brain, was what differentiated those addicted to marijuana and those who aren’t.

“What we saw was a distinctly different coherence of reward regions for our dependent users as compared to non-dependent users so the functional connectivity for that hub of reward circuitry was distinctly different for dependent users than non-dependent users,” he said.

And while marijuana remains to be the most widely used illicit drug in the United States, according to a study by the National Survey on Drug Use and Health, it’s starting to be regulated and used recreationally in states such as Colorado and Washington, leaving more room for scientists to study the drug, its affects and dependence.

“It’s really useful for us as scientists in terms of putting together architecture of how the brain of a substance using individual is set up,” said Dewitt.

He said that the purpose of Dr. Filbey’s research is to objectively look at the impact of marijuana on those addicted to the substance.

“The goal of Filbey’s lab is not really to cast a light on cannabis as a whole one way or the other,” said Dewitt. “But we know that there is a subset of any population that struggle with substance abuse and we really want to identify the factors for the individuals that struggle with substance abuse related to cannabis use, what is it that’s defining the problem for them.”

Filbey said in an interview for public radio that what’s next in her research is studying the long-term effects of marijuana, as well as the genetic and environmental factors such as stress on dependent and non-dependent users.


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