Indiana University Bloomington

IU study of brain networks in marijuana users receives a $275,000 NIH grant

  • Oct. 21, 2014

FOR IMMEDIATE RELEASE

BLOOMINGTON, Ind. -- Researchers in the Indiana University Bloomington Department of Psychological and Brain Sciences were awarded a $275,000 grant from the National Institutes of Health to study the effects of marijuana on brain connectivity in both current and former users.

Led by professor Brian O’Donnell and associate professor Sharlene Newman, the study will analyze how marijuana use affects both brain networks and specific regions. It will be the first study to apply network analysis to understand changes in brain connectivity related to current and past marijuana use.

The researchers will pursue a number of questions, including how its use might alter the course of brain development in adolescence and early adulthood; whether earlier use would cause more severe effects; how much is too much for particular age groups; and whether discontinuing use allows for recovery.

“Given the recent decriminalization of marijuana in several states and its widespread use, there is an urgent need to determine how marijuana affects the brain, and whether such changes are related to those observed in psychotic disorders,” O'Donnell said.

Cannabis sativa (marijuana), which according to surveys has been used by more than 30 percent of the adult population in the United States, is known to affect several aspects of mental functioning, including attention, learning and judgment of time. It can also induce symptoms typical of psychosis, such as paranoia and sensory distortions.

Studies across a number of countries have also found that adolescents who use cannabis are at a higher risk of developing schizophrenia, a psychotic disorder, later in life. O’Donnell, a schizophrenia researcher, suggests that while scientists don’t know if it directly causes schizophrenia, for those with a genetic risk for this illness, cannabis may contribute to its occurrence. He points out that more than 40 percent of schizophrenia patients use cannabis.

A pilot study published by O'Donnell and Newman's research group indicated that brain networks in people who used marijuana were less efficiently organized than those in non-users. Yet, “the effect of cannabis on the organization of the brain is still little understood,” O’Donnell said. In part, he said, this is because of the difficulty of studying an illegal substance classified as a narcotic.

The research team includes IU computational neuroscientist Olaf Sporns, whose pioneering work on brain network analysis helps conceptualize the interaction between different parts of the brain. The current project will draw on the measures Sporns has developed to look at network properties as a whole and the pathways that connect the nodes within the neural systems under investigation. As Sporns' research shows, networks that facilitate the interaction and exchange of information between brain regions are necessary for nearly all, even the simplest, physical and mental tasks.

Cannabis affects several brain functions, including pain perception and our sense of time, as well as learning and memory, O'Donnell said. As such, it has a wide-ranging effect on the brain, especially as these systems develop.

“We know from other studies where the cells that respond to cannabis are located in the brain, so we can zero in on a region that has a high density of these receptors," O'Donnell said. "They are dense, for example, in the hippocampus, which is involved in learning and memory, and are present in the cerebellum, which is critical for coordination of movement and involved in our perception of time.”

Cannabis is also unlike other drugs such as opiates, nicotine and cocaine, which are highly addictive and which reshape the brain to seek out more of the drug.

“While many drugs rapidly decay and leave your system, cannabis stays in your body for weeks, so that, even though you may not feel high for more than a few hours, some of the physiological effects are still present,” O'Donnell said.

The researchers are now getting ready to recruit three groups of 30 people, ages 18 to 40, to participate in the study. One group will include current users. Another group will include those who have used it in the past but have quit for at least a year. The third will consist of people who have never used cannabis. The challenge will be finding people who smoke marijuana but don’t use any other drugs or drink heavily. Participants must also be without serious mental illness or incidence of head trauma.

In addition to using brain-imaging technology to explore the organization of brain networks, the researchers will give the candidates various tests of memory and attention. They will also interview candidates about how much and how long they took marijuana and test them for personality traits that often accompany its use, such as unusual beliefs and odd perceptions, which are often seen in psychotic disorders.

O'Donnell said the project offers a unique opportunity to bring together “an extraordinary group of researchers to address a public health problem of enormous importance, given the widespread use of cannabis and the trend toward legalization in many states.”

In addition to Sporns, researchers include IU neuroscientist Ken Mackie, a consultant on the project who has done fundamental research into the brain systems on which cannabis acts. Also on the team are brain-imaging experts, Dai-Jin Kim, Aina Puce and Newman, who is also co-principal investigator, as well as William Hetrick, a schizophrenia researcher and chair of the IU Department of Psychological and Brain Sciences. The study will be funded for two years.

“There’s a popular perception that marijuana is a relatively benign drug," O'Donnell said. "My guess is that this may not be the case.”

To learn more about the project or to speak with O’Donnell, contact Liz Rosdeitcher at rosdeitc@indiana.edu or 812-855-4507 or Tracy James at 812-855-0084 or traljame@iu.edu. The Department of Psychological and Brain Sciences is in the IU Bloomington College of Arts and Sciences.

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Brian O'Donnell

Brian O'Donnell | Photo by Indiana University

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Sharlene Newman

Sharlene Newman | Photo by Indiana University

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The brain’s communication pathways can be traced using diffusion tensor MRI and fiber tractography (shown in the right part of the figure). Connections from different parts of the brain construct the brain network with a number of nodes and edges (left).

The brain’s communication pathways can be traced using diffusion tensor MRI and fiber tractography (shown in the right part of the figure). Connections from different parts of the brain construct the brain network with a number of nodes and edges (left). So far, many forms of brain dysfunction have been conceptualized as network diseases. This study will determine how past and current cannabis use affects brain network characteristics when compared to no use. | Photo by Indiana University

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Media Contacts

Liz Rosdeitcher

  • Department of Psychological and Brain Sciences
  • Office 812-855-4507
  • rosdeitc@indiana.edu

Tracy James