Biomarker Associated with Chronic Stress and Anxiety Found in Higher Levels in Long-Term Young Cannabis Users
A first of its kind study involving researchers from the University of Toronto’s Faculty of Medicine and the Centre for Addiction and Mental Health published in the journal JAMA Psychiatry has found elevated levels of a protein involved in immune function and associated with chronic stress and anxiety in the brain of young long-term cannabis users.
This study was funded by a grant from the U.S. National Institute of Mental Health.
“Cannabis is the most commonly used illicit drug in the world but we know very little about the impact it has on the brain, especially in young users whose brains are still developing until the age of 25,” said Dr. Romina Mizrahi, lead author of the paper. Mizrahi is head of the Focus on Youth Psychosis Prevention Clinic and research program, as well as head of the Psychosis PET program in the Research Imaging Centre and Clinician Scientist in the Campbell Family Mental Health Research Institute at the Centre for Addiction and Mental Health. Dr. Mizrahi is also an associate professor at the University of Toronto’s department of psychiatry, in the faculty of medicine, and a faculty member in the faculty’s pharmacology and toxicology department.
“These findings are an important step forward, but more studies are needed to better understand the role of cannabinoids and neuroimmune signaling.”
Using a Positron Emission Tomography (PET) tracer developed at CAMH, this is the first study to investigate whether there is an association between cannabis and neuroimmune function in the brain. Specifically, the study found elevated levels of a brain protein – called ‘TSPO’ – associated with higher levels of stress and anxiety in young long-term cannabis users compared to young non-cannabis users.
The study does not prove a link between long-term cannabis use and stress and anxiety because it is not yet known why there are elevated levels of TSPO in the brains of young cannabis users. Dr. Mizrahi says the next step in future research is to see if TSPO normalizes following cannabis abstinence, and if stress and anxiety levels also return to normal after young people stop using cannabis.
“We are hoping we can replicate and expand this finding to further evaluate if this biomarker goes back to normal levels after people abstain from cannabis use” said Dr. Mizrahi.
CAMH experts participated in the development of the Lower-Risk Cannabis Use Guidelines – an evidence-based tool that helps people understand the risks associated with cannabis use. CAMH’s Youth Engagement Team has worked to adapt the guidelines for young people and has created a pocket-sized guide for youth that uses a conversational tone to help explain the health and safety risks of cannabis and 10 recommendations to reduce these risks.
The paper also involved additional researchers with a relationship to University of Toronto.
Tania Da Silva is a University of Toronto MSc graduate, and now works as a research analyst at the Centre for Addiction and Mental Health neuroimaging in early psychosis group.
Dr. Pablo Rusjan is a research scientist at the Research Imaging Centre at the Centre for Addiction and Mental Health, and an associate professor at University of Toronto’s faculty of medicine.
Dr. Jeffrey Meyer is head of the neurochemical imaging program in mood disorders in the Research Imaging Centre, based in the Campbell Family Mental Health Research Institute at the Centre for Addiction and Mental Health. He is also a professor at the University of Toronto’s faculty of medicine, and a Canada Research Chair in Neurochemistry of Major Depression.
Dr. Sylvain Houle is a senior scientist and former founding director of the Research Imaging Centre and Preclinical Research in the Campbell Family Mental Health Research Institute at the Centre for Addiction and Mental Health, and an associate professor at University of Toronto’s faculty of medicine.
Jeremy Watts is a student-researcher at the Centre for Addiction and Mental Health and a PhD candidate at University of Toronto’s faculty of medicine.
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