While the short-term effects of marijuana are undeniable, the debate on whether long-term damage is possible has been ongoing ever since it was labeled as a poison and banned in the 1920s. The majority of studies in the past have been flawed for the most part, with some testing “long term effects” in as little as 28 days (marijuana stays in the system for at least a month for people with average body fat levels) and comparing smokers with non-smokers without testing the smoking group beforehand to see if anything had changed to begin with. However, a recent study has finally scratched the surface of addressing the question of long-term use.
The study, conducted by Northwestern Medicine, examined the possibility of cognitive deficits in regular smokers as far as two years into the future. The test group involved participants in their early 20s with around three years of regular use. Using memory tests and brain scans, the researchers found abnormal changes in brain structure and reductions in working memory. Working memory refers to the mind’s ability to store short-term information and move it to longer-term networks in the brain if need be. A poor working memory can lead to many issues with basic functioning, work performance and interpersonal relationships.
The neural structures related to memory in the test group appeared to shrink inwards in the brain scans, suggesting either a literal decrease in neurons or reduced activity. Although a reduction in neural activity will eventually cause the brain to deactivate certain networks for the sake of efficiency, it is unclear whether two years is sufficient to permanently shut off the networks, especially since some studies have found THC and CBD (the chief psychoactive compounds in marijuana) to preserve neural degeneration.
Similar to other studies on marijuana, the researchers also found schizophrenia-like symptoms in the brain, with communication amongst the brain’s various regions acting abnormally. However, how exactly the communicational patterns were different were not elaborated on by the researchers; disjointed areas of the brain can entail many different scenarios, with the symptoms of schizophrenia itself being one of the most diverse due to this very reason.
Earlier use and increased risk
Possibly the strongest evidence that long-term marijuana use does have a lasting adverse effect with chronic use is its tendency to cause more cognitive abnormalities in smokers that start at a younger age. Another study carried out by a team from the University of Melbourne, Australia used MRI scans on regular smokers that started in adolescence, finding an impairment in neural connections between the two hemispheres of the brain. Compared with the control group of non-smokers, this reduction in connections may suggest cognitive degeneration with early marijuana use, although there were no MRIs taken before for both groups to confirm if any brain structures did indeed change. However, the smokers who started earlier showed more pronounced impairments, suggesting a correlation between age and changes in the brain.
Similarly, a much more major study by New Zealand researchers that followed over a thousand regular smokers from birth to their late thirties found that the ones that started in their teens scored lower on IQ tests in their thirties than when they were children. However, there were no links found between the earlier/lower IQ smokers and differences in socioeconomic status, drug use, mental health disorders or personality. The researchers also gave questionnaires regarding their memory to the participants’ family members or roommates, with the ones who smoked the most frequently as teens being described as having the most difficulty in daily life.
Although it appears that chronic use of marijuana can definitely result in cognitive changes, the question of whether or not real brain damage is occurring requires more causal research, something that is still considered unethical in humans with our current technology.
If you would like to learn more about the effects of marijuana or other recreational drugs, feel free to browse the reviews section of our site or contact us today.
Written by Chase Beckwith, Sovereign Health Group writer