Healthcare (Commonwealth Union) – Cannabis, also known as marijuana, weed, or pot, is a psychoactive drug derived from the Cannabis sativa plant. It has been used for centuries for medicinal, recreational, and spiritual purposes. In recent years, attitudes toward cannabis have shifted, with many countries and states legalizing its use for medical and even recreational purposes. However, debates continue regarding its health effects, societal impact, and regulation.
A new study led by McGill University has found that individuals with cannabis use disorder (CUD) show increased dopamine activity in a part of the brain linked to psychosis.
The lead author Jessica Ahrens, a PhD candidate in McGill’s Integrated Program in Neuroscience indicated that this could shed light on why using cannabis may heighten the risk of experiencing hallucinations and delusions—core features of schizophrenia and other psychotic conditions.
Researchers of the study pointed out that dopamine, a chemical messenger in the brain, plays a role in controlling mood and motivation. When present in excess, it’s been associated with the development of psychosis. Although it’s been previously understood that cannabis affects dopamine levels, this research identifies the specific brain region where these changes take place. Cannabis use disorder refers to a pattern of problematic cannabis consumption, where individuals struggle to limit use, continue despite harmful consequences, and may go through cravings or withdrawal symptoms.
Ahrens indicated that for years, scientists have been trying to prove that cannabis impacts the brain in a way that contributes to psychosis, but their research now points to a shared dopamine-related pathway that could be the missing link.
The research examined 61 participants, including individuals both with and without cannabis use disorder, as well as people in the early stages of schizophrenia—some of whom also had CUD. Scientists at Western University used a specialized brain imaging technique known as neuromelanin-MRI to assess levels of neuromelanin, a marker that indicates dopamine activity in the brain.
Those diagnosed with CUD showed unusually high neuromelanin signals, with the increase correlating to how heavily they used cannabis. In comparison, participants who did not have schizophrenia or CUD did not exhibit elevated levels. Additional research with a larger sample size will be necessary to validate these results.
Researchers of the study took into account that approximately 20 percent of youth in Canada use cannabis on a daily or near-daily basis. Gaining a clearer understanding of how the substance affects mental health continues to be a critical concern.
“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,” explained Dr. Lena Palaniyappan, a Professor of Psychiatry at McGill University as well as a 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,” Dr. Palaniyappan explained.
Future research is set to investigate if prolonged cannabis uses results in permanent dopamine alterations and if these impacts are reversible after cessation.
Often referred to as the “feel-good” chemical, dopamine is released in response to rewarding experiences such as eating delicious food, engaging in sexual activity, or receiving praise. This release of dopamine reinforces behaviors that are essential for survival and reproduction.
However, dopamine is not just about pleasure. It also plays a critical role in motivation and goal-directed behavior. When we anticipate a reward, our brains release dopamine, which motivates us to take action towards achieving that reward. This is why dopamine is often associated with feelings of motivation, focus, and drive.
The study “Convergence of Cannabis and Psychosis on the Dopamine System” by Jessica Ahrens, Clifford Cassidy, and Lena Palaniyappan et al., appeared in the journal Jama Psychiatry.
