A groundbreaking study led by McGill University has found that individuals with cannabis use disorder (CUD) exhibit elevated dopamine levels in brain regions associated with psychosis. These findings could help explain the increased risk of hallucinations and delusions, which are hallmark symptoms of schizophrenia and other psychotic disorders, in cannabis users.
Dopamine is a neurotransmitter that plays a critical role in regulating mood, motivation, and reward. An excess of dopamine in certain brain regions is linked to psychosis, a condition characterized by distorted thinking, hallucinations, and delusions. While it was previously known that cannabis influences dopamine levels, this study provides clarity on where in the brain these changes occur, particularly in individuals with cannabis use disorder (CUD).
“For a long time, clinical researchers across the world have been searching for a link showing that cannabis affects the brain mechanism behind psychosis. We now show that a shared dopamine pathway could be the answer,” said Jessica Ahrens, the first author of the study and a PhD student in McGill’s Integrated Program in Neuroscience.
The study involved 61 participants, including individuals with and without cannabis use disorder, as well as people with early-stage schizophrenia, some of whom also had CUD. Using a specialized brain scan called neuromelanin-MRI, researchers measured the neuromelanin signal, which reflects dopamine activity in the brain.
The results revealed that individuals with CUD had significantly higher neuromelanin signals, indicating elevated dopamine activity. This increase in dopamine was directly related to the severity of their cannabis use. In contrast, participants without schizophrenia or CUD did not show these elevated dopamine levels, suggesting a clear association between cannabis use disorder and dopamine dysregulation in areas linked to psychosis.
The study’s findings could have important implications for understanding how cannabis use may contribute to the development of psychotic disorders. Elevated dopamine levels in CUD individuals may provide a biological basis for why cannabis use increases the risk of psychosis. This could help clinicians better educate patients—especially young people and those with a family history of psychosis—about the risks associated with frequent cannabis use.
“The lack of clear biological evidence linking cannabis to psychosis has made it harder to persuade young people with psychotic symptoms to reduce their use,” said Dr. Lena Palaniyappan, Professor of Psychiatry at McGill and psychiatrist at the Douglas Mental Health University Institute. “Our findings could help doctors and mental health professionals better educate patients about the potential risks of frequent cannabis use, especially for those with a family history of psychosis.”
While this study sheds light on the relationship between cannabis use and dopamine dysregulation, more research is needed to confirm these findings in larger populations. Future studies will explore whether long-term cannabis use results in lasting changes to dopamine activity and whether these effects are reversible after cessation of cannabis use.
This research underscores the need for ongoing investigations into the impact of cannabis on mental health, particularly given the rising rates of cannabis use among young people and its potential links to psychiatric disorders such as psychosis and schizophrenia.
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