A landmark study conducted by researchers at the Centre for Addiction and Mental Health (CAMH) found elevated levels of a brain protein associated with chronic stress and anxiety in the brains of young long-term cannabis users.
Published on September 18 in the JAMA Psychiatry medical journal, this study was one of the first to use the Positron Emission Tomography (PET), an imaging technique, to study the association between cannabis and the neuro-immune function in the brain.
The brain protein that was studied is called a translocator protein, or TSPO. It is involved in immune functions and is associated with levels of stress and anxiety.
In an interview with The Varsity, Dr. Romina Mizrahi, the lead author of the study and Senior Scientist at the CAMH Research Imaging Centre, talked about the motivation behind the research.
“Young people use cannabis a lot and they usually think or perceive cannabis as harmless,” she said.
“I, as a scientist, I know that the brain develops and is still developing until the age of 25, so I wanted to understand how cannabis affects the developing brain.”
The study’s design and results
Mizrahi and her co-authors conducted the study in Toronto. The participants included 24 long-term cannabis users, who met the criteria for Cannabis Use Disorder (CUD).
The study also consisted of 27 non-cannabis users, who acted as the control group to compare the protein levels in the brain.
Each participant underwent a scan with the PET imaging technique, which the researchers used to measure the subjects’ levels of TSPO.
The study found that long-term cannabis users had significantly higher levels of the biomarker associated with stress and anxiety compared to the non-users.
Limitations of the study
Mizrahi warns readers, however, that this experiment only studied the relationship between cannabis use and the biomarker associated with stress.
While she and her co-authors studied the biomarker’s levels, they did not examine the impact of its elevated levels on the subjects’ behaviour. The study therefore does not provide a direct link between long-term cannabis use and the symptoms of stress and anxiety.
“We cannot say that cannabis causes this increase in this protein or that it causes stress and anxiety,” said Mizrahi. “We know they are related, but we don’t know which comes first.”
However, Mizrahi spoke about the potential future research that aims to study causation. Such studies could also examine whether the biomarker’s levels would normalize after a period of abstinence for long-term cannabis users.
These findings could refine research and have major future implications regarding attitudes toward the consumption of cannabis for adolescents.
Effects of cannabis on the developing brain still unknown
Mizrahi still added that she would caution adolescents against using cannabis due to their developing brains.
“What I would tell them is that they should be careful when using cannabis because their brains are still developing until the age of 25,” she said. “Whether [the effects are] long-term or short-term, we need to study this moving forward.”
“But I would still caution them not to use cannabis. To use or to not use cannabis while the brain is developing… is an important decision [that adolescents] have to make.”