Lower dopamine in heavy users of marijuana can affect cognitive abilities: Study
Not all quarters are happy with the legalization of medicinal marijuana in 24 American states and Washington D.C. and decriminalization of marijuana for recreational purposes in four states. This group looks at the drug with mistrust and believes that a final decision on the use of the drug must be taken only after being armed with complete information about its effects and impact.
A recent study by the Columbia University Medical Center (CUMC), published in the Molecular Psychiatry in March 2016, has given a reason to the skeptical group to stand firm on their belief. It suggested an adverse effect on the dopamine system in cannabis-dependent individuals, thus, associating the drug with deficiency problems in learning and memory.
Considering how drugs such as cocaine and heroin lead to compromised dopamine release in addicts, the scientists wanted to see if the same effects could be observed in cannabis users.
The study, titled “Deficits in striatal dopamine release in cannabis dependence,” was conducted on 11 adults aged between 21 and 40 years who excessively used marijuana, and compared them with 12 healthy adults with matching age and gender details.
Long-term, heavy cannabis use may impair dopaminergic system
The scientists noted that the severely dependent users of cannabis had resorted to using drugs by the time they touched 16, had become addicted to it by the time they reached 20 and have been addicted to it for the past seven years.
They also observed that in the previous month, approximately all the users smoked cannabis on a daily basis. Lead author of the study Dr. Anissa Abi-Dargham, a professor of psychiatry (in radiology) at the (CUMC), said, “In light of the more widespread acceptance and use of marijuana, especially by young people, we believe it is important to look more closely at the potentially addictive effects of cannabis on key regions of the brain.”
For the purpose of the research, the scientists used the positron emission tomography (PET) to trace a radiolabelled molecule that binds itself to the dopamine receptors in the brain. They evaluated and quantified the release of dopamine in the striatum and its subregions, apart from other regions outside the striatum, including the thalamus, midbrain and globus pallidus.
The marijuana users were confined to hospital for seven days without the drug to make sure that the PET scans were not assessing the severe impact of the drug. The respondents were scanned prior to and after being administered oral amphetamine to induce the release of dopamine. The percentage change measuring the binding of the radiotracer pinpointed to the capacity for dopamine release.
Though the researchers are not sure as to whether reduced dopamine levels existed prior to the study or was the outcome a result of incessant marijuana use, Abi-Dargham said, “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.”
The findings of the study are important in the light of the fact that an estimated 6 million Americans suffer from marijuana use disorder, according to the National Institute on Alcohol Abuse and Alcoholism (NIAAA).
Path to recovery
Stressing on the importance of the research, Dr. Jeffrey Lieberman, Chair, Psychiatry at the CUMC, ex-president of the American Psychiatric Association, said, “These findings add to the growing body of research demonstrating the potentially adverse effects of cannabis, particularly in youth, at the same time that government policies and laws are increasing access and use.”
Most of the Americans seem to be addicted to one substance or the other. This is not the first time that scientists have expressed their apprehension regarding marijuana smoking habits. Previous studies have also pointed that unrelenting marijuana use can hamper cognitive abilities of an addict.
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