Cannabis has a long and complex history, dating back thousands of years. The oldest known written record of cannabis use comes from Emperor Shen Nung of China in 2727 B.C., who documented its medicinal properties. The plant was also known to Ancient Greeks and Romans, and its use spread throughout the Islamic empire, reaching North Africa. Over centuries, cannabis was valued for its therapeutic, recreational, and industrial applications. Although cannabis has been found to have beneficial medicinal effects for patients who have certain medical issues, for decades, concerns have existed regarding a possible connection between the use of cannabis, and effects on brain functions such as cognizance and memory. But for most of the 20th century, medical research on cannabis was extremely limit due to legal, political, and regulatory barriers. In 1937, the U.S. passed the Marijuana Tax Act, which heavily regulated and effectively criminalized cannabis. This discouraged research by making it difficult to legally obtain cannabis for studies. In 1970, the Controlled Substances Act (CSA) classified marijuana as a Schedule I drug, meaning it was considered to have no accepted medical use and a high potential for misuse, a classification it still holds at the federal level. Schedule I status made it nearly impossible for researchers to access cannabis legally, as obtaining government approval required navigating complex and time-consuming bureaucratic processes. Until recently, the only federally approved source of cannabis for research in the U.S. was the University of Mississippi, which grew marijuana under a contract with the National Institute on Drug Abuse (NIDA). This limited supply meant that researchers could not study different strains or potencies commonly available in legal markets today. The "War on Drugs" in the 1980s and 1990s led to anti-cannabis propaganda, further discouraging funding and interest in medical cannabis research. Fear of losing funding or facing professional consequences*made many scientists and institutions hesitant to study cannabis. Most medical research is funded by government agencies, universities, or pharmaceutical companies. Because cannabis was illegal and not patentable, pharmaceutical companies had little financial incentive to invest in cannabis research. Federal funding agencies prioritized research on cannabis harms rather than potential benefits. In 1996, California legalized medical cannabis, leading to increased public interest in studying its effects. In 2014, the U.S. allowed more research access by passing the Farm Bill, which permitted limited hemp-derived cannabinoid studies. In 2021, the DEA announced an expansion of cannabis cultivation licenses, allowing more institutions to grow research-grade cannabis. More recently, state-level legalization has led to more independent studies, but federal restrictions still limit large-scale clinical trials. The combination of legal barriers, lack of access, stigma, and lack of funding prevented serious medical research on cannabis for decades. However, as legalization expands and restrictions loosen, research into cannabis’s medical benefits is finally progressing, providing new insights into its potential therapeutic applications. In the largest study to date, regarding cannabis use and its effects on brain function, researchers at the CU Anschutz Medical Campus used functional MRI imaging to examine over a thousand young adults aged 22 to 36, in order to evaluate how their recent and lifetime cannabis use has affected their neural activity across different cognitive tasks. It's not surprising that this study would focus on negative effects of cannabis, rather than medicinal benefits, since the study appears to have been funded mostly by various government grants. The study was published in JAMA Network Open (Gowin, et al., 2025).1 The study found that: Cannabis use is linked to reduced brain activity during working memory tasks.
The regions of the brain most affected were:
These areas are responsible for decision-making, memory, attention, and emotional regulation. Working memory decline is statistically significant.
Other cognitive tasks were less affected. The study tested seven cognitive functions, including:
Considering recent use versus lifetime use: Both recent cannabis use (detected via urine screening) and heavy lifetime use (>1,000 instances) led to lower brain activation. Long-term use had a more persistent effect, even when adjusting for recent consumption. This suggests that long-term cannabis use may have lasting effects on brain function, rather than just short-term impairment. Abstaining tends to improve cognitive performance. Although quitting cannabis use before performing cognitive tasks may help recover some function, heavy users may experience withdrawal related cognitive impairments when stopping suddenly. The study suggests that longer abstinence periods may be required for full cognitive recovery. Limitations of the study, included several confounding possibilities. Although the study was adjusted for factors like age, sex, race, education, income, alcohol, and nicotine use, no assessment was made for any psychiatric conditions (for example, ADHD, anxiety, or depression). It should be noted that such issues often tend to be a primary reason why some individuals choose to use cannabis, in the first place, and that might, or might not, affect the findings of the study. Also, there was no long-term follow-up to determine if cognitive function normalizes after prolonged abstinence. And cannabis use history in this study was self-reported, which obviously introduces some risk of underreporting, or misclassification. There were no surprises in the findings of this study. The study only confirmed what we all suspected — that heavy cannabis use has negative effects on cognizance and memory. But the same can be said for many prescription drugs manufactured by Big Pharma. So if cannabis is being used to mitigate the symptoms of PTSD or some other health syndrome, the resulting symptoms and side effects of cannabis use may be acceptable. On the other hand, if it's being used strictly for recreational purposes, then the cost in terms of negative mental health attributes is considerable. But then, that's true of virtually all drugs used for recreational purposes. There are other reasons why medical research often focuses on the negative aspects of cannabis use. Compromised cognizance and memory aren't the only problems associated with cannabis use. Another serious problem that many daily cannabis users have to deal with is a condition known as cannabinoid hyperemesis syndrome (CHS). Contrary to cannabis’s well-known ability to ease nausea—especially in cancer patients undergoing chemotherapy—CHS triggers cyclical bouts of severe nausea, uncontrollable vomiting, and excruciating abdominal pain. The only known cure is stopping cannabis use entirely. A study by researchers at George Washington University, and published in the annals of emergency medicine, surveyed 1,052 individuals who reported suffering from CHS (George Washington University, 2025, February 20; Meltzer, et al., 2025).2,3 They found that:
Although CHS appears to present a serious risk for long-term cannabis use, it seems only fair to point out that many high dollar medical drugs have a similar problem — after a few years of use, many so-called "biologicals", for example, provoke the immune system so that it develops an allergic reaction to the drugs, for many patients. Other drugs (corticosteroids come to mind, for example) slowly lose efficacy, so that they eventually provide little to no benefit. Is cannabis useful for MC patients? The jury is still out on that issue, with a few users posting on the MC Discussion and Support Forum that it helps suppress their MC symptoms (especially pain), while others say that it doesn't seem to help. Back in October, 2016, the Microscopic Colitis Foundation published a newsletter that discussed the possibility of using cannabis to treat IBD symptoms. For those who wish to review the article in the newsletter, here's a direct link to that newsletter: https://www.microscopiccolitisfoundation.org/uploads/5/8/3/2/58327395/final_corrected_copy_of_october_1_2016_newaletter_5_for_website.pdf References: 1. Gowin, J. L., Ellingson, J. M., Karoly, H. C., Manza, P., Ross, J. M., Sloan, M. E., . . . Volkow, N. D. (2025). Brain Function Outcomes of Recent and Lifetime Cannabis Use. JAMA Network Open, 8(1), e2457069. Retrieved from https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2829657 2. George Washington University. (2025, February 20). Daily cannabis use linked to public health burden. ScienceDaily, Retrieved from https://www.sciencedaily.com/releases/2025/02/250220122931.htm 3. Meltzer, A. C., Morrison, C., Loganathan, A., Shahamatdar, S., Moon, A., Heidish, R., . . . Cooper, Z. D. (2025). Cannabinoid Hyperemesis Syndrome Is Associated With High Disease Burden: An Internet-Based Survey. Annals of Emergency Medicine, 0(0). Retrieved from https://www.annemergmed.com/article/S0196-0644(25)00018-6/abstract
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