Excessive cannabis use causes dopamine signaling to spin out of control in a part of the brain that is strongly linked to schizophrenia, new research reveals. Using brain imaging techniques, the study authors were able to observe black spots in this critical neurological region, providing the clearest evidence yet for a direct link between cannabis and psychosis.
These dark regions are caused by a pigment called neuromelanin, which is left behind when dopamine levels rise too high. A key neurotransmitter that helps to regulate mood, motivation and cognitive function, dopamine also contributes to a range of mental health conditions when its concentration in the brain becomes unbalanced.
For instance, previous research has shown that people with schizophrenia tend to have increased dopamine levels in a brain region called the dorsal striatum, which is fed by neurons in the substantia nigra [SN] and ventral tegmental areas [VTA]. Given that cannabis use has been associated with psychosis, the study authors decided to investigate whether elevated dopamine levels could also be seen in these same brain regions in individuals who regularly use pot.
Using neuromelanin-sensitive magnetic resonance imaging, the researchers scanned the brains of 61 people – 25 of whom had been diagnosed with cannabis use disorder – in search of black spots in the specific parts of the SN and VTA that are associated with psychosis. Sure enough, they found a dose-dependent increase in neuromelanin within these regions, meaning that heavier cannabis use was linked to larger black spots.
“In people partaking in excess cannabis use, those spots are blacker than what they should be for their age compared to healthy individuals,” said study author Lena Palaniyappan in a statement. “This indicates they have high levels of dopamine, and in some cases are showing pigments someone 10 years older would have.”
Worryingly, this increase was detected in all participants with cannabis use disorder, including those who had never experienced an episode of psychosis. However, the association between excessive cannabis use and enhanced neuromelanin was twice as strong in those who had suffered a psychotic event.
“We saw an increase of blacker spots in a particular region of the midbrain associated with psychosis – the substantia nigra and ventral tegmental areas,” said study author Ali Khan. “This increase was seen in those with cannabis use disorder regardless of whether they have first-episode schizophrenia,” he continued.
Putting these findings into context, Palaniyappan concluded that “we now have evidence that shows a straight line linking cannabis with dopamine and psychosis that has never been shown before, and it’s crucial that clinicians, patients, and families work together to break this line.”
The study is published in the journal JAMA Psychiatry.
Source Link: Black Brain Spots Reveal Possible Direct Link Between Cannabis Use And Psychosis
