This article was updated on September 23, 2021.
Recent clinical literature suggests that the most active compound in marijuana, THC (tetrahydrocannabinol) can effectively mitigate symptoms associated with anxiety, depression, and even certain types of cancer. However, research finds habitual marijuana users could be at higher risk for developing Alzheimer’s Disease.
The connection between marijuana and Alzheimer’s onset
The study, published in the Journal of Alzheimer’s Disease, looked at a pool comprised of 2,600 participants.
The authors set out to determine whether the passage of blood (perfusion) in specific brain regions on functional neuroimaging (like populations affected by Alzheimer’s disease) is altered for the worse in habitual marijuana users.
The subjects featured in the report were segmented into two groups: the control, which did not regularly consume cannabis, and the experiment group, which routinely did.
Neuroimaging was captured via single-photon emission computed tomography, referred to more commonly as SPECT.
According to the findings, blood flow was dramatically lower in every area of the brain among the experiment group. This was especially true of the hippocampus–a region epicentral to the diagnosis of neurodegeneration. Atrophy of the hippocampus is a key feature of Alzheimer’s disease specifically.
“Few studies have evaluated the impact of marijuana use on regional cerebral blood flow,” the authors wrote in the new paper. “Multiple brain regions show low perfusion on SPECT in marijuana users. The most predictive region distinguishing marijuana users from healthy controls, the hippocampus, is a key target of Alzheimer’s disease pathology. This study raises the possibility of deleterious brain effects of marijuana use.”
Implications for marijuana administration in Alzheimer’s
Over time, reduced blood flow to the hippocampus impairs our ability to store memories and complete daily tasks.
“As a physician who routinely sees marijuana users, what struck me was not only the global reduction in blood flow in the marijuana users’ brains but that the hippocampus was the most affected region due to its role in memory and Alzheimer’s disease,” says Dr. Jorandby, who worked on the new paper.
These implications aren’t exactly novel, but the exhaustive mechanisms by which they were confirmed are. Those deemed to be suffering from cannabis use disorder were meticulously compared to those who rarely smoked or didn’t do so at all.
“Persons with a diagnosis of cannabis use disorder by DSM-IV and DSM-V criteria (n = 982) were compared to controls (n = 92) with perfusion neuroimaging with SPECT at rest and at a concentration task. Perfusion estimates were quantified using a standard atlas. Cerebral perfusion differences were calculated using one-way ANOVA. Diagnostic separation was determined with discriminant analysis of all subjects,” the authors said of their methodology.
Even among supporters, it is generally believed that recreational cannabis use should be monitored carefully by the user.
The problem is buzzword issues tend to get bogged down by slogans and agendas. There isn’t a body occupying a public office that doesn’t have a lot to lose and gain by reason of their stance on marijuana consumption.
Kevin Hill, associate professor of psychiatry at Harvard Medical School and director of the Division of Addiction Psychiatry at Beth Israel Deaconess Medical Center, attempts to cut through the political brush and bramble in service of an honest assessment of the popular drug.
“We know a lot more about both the benefits and the risks of cannabis use, although I would say that the rate and scale of research has not kept pace with the interest. There is a growing body of literature on the therapeutic use of cannabis and, similarly, we’re learning bits and pieces about the problems associated with cannabis use. But our increased knowledge pales in comparison to the intense public interest, so one of the issues we often encounter is a growing divide between what the science says and what public perception is,” Dr. Hill wrote of his recent dissertation on the topic.
“Dose matters. When we talk about the harms of cannabis, young people using regularly can have cognitive problems, up to an eight-point loss of IQ over time. It can worsen depression. It can worsen anxiety. But all of those consequences depend upon the dose. The data that shows those impacts look at young people who are using pretty much every day. They’re heavy users who usually meet criteria for cannabis-use disorder. So when people who are opposed to cannabis talk about those harms, they don’t mention that.”
If we appreciate the research literature as a lodestar of sorts in our ongoing cannabis debate, we understand that like anything else, the drug works the best when used in moderation and it inflicts the most harm when users are dishonest with themselves about its destructive potential.