Researchers at Columbia University Medical Center have released the results of a study that suggest heavy cannabis use may result in a dopamine deficiency in the brain.
Dopamine is a neurotransmitter in the human brain which is responsible for reward behavior. Unlike natural sensations that trigger dopamine release, substances like cocaine and opioids cause dopamine to be released at a much higher level. Scientists focus on dopamine levels when evaluating the potential addictive effects of drugs. With long-term use, the brain becomes dependent on the substance to release dopamine in healthy amounts.
The study tracked 11 individuals who use cannabis heavily and 12 healthy control subjects. All of the test participants used cannabis daily in the month prior to the test. During the testing process, all participants were kept in a hospital for a week to abstain completely from cannabis. This was done to ensure that the positron emission tomography (PET) used to track dopamine in the brain wasn’t simply measuring the effects of cannabis.
Researchers focused on the area of the brain known as the striatum, which is the part of the brain that receives and responds to dopamine. In other words, if dopamine is gasoline, the striatum is the engine. By using both the PET test and cognitive tests designed to determine brain functions like memory and thought processes, the study was able to compare how heavy cannabis use affects the brain. What they found was that heavy cannabis users had lower dopamine levels and reduced cognitive function compared with the 12 control subjects.
“We don’t know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use,”
said Dr. Abi-Dargham, the author of the study.
“But the bottom line is that long-term, heavy cannabis use may impair the dopaminergic system, which could have a variety of negative effects on learning and behavior.”
In addition to dopamine, researchers also took the opportunity to measure glutamate in the brain. Glutamate is another neurotransmitter that acts as a messenger between the brain and nerve cells, and has an impact on memory. While it has been suggested that cannabis can trigger schizophrenic symptoms by adjusting glutamate levels, researchers did not find any fluctuation in glutamate in this study.
While the researchers conducting this study admit that the test was inconclusive, given the small test group and other factors, it did suggest that cannabis use in moderation resulted in healthier brain function.