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The Top Cannabis Science Articles of 2021

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Below, we round up a selection of some of the most striking and significant news we’ve covered in the past year – from cannabinoid breakthroughs to plant science progress. Enjoy!


Cannabis vs opioids. A study combining data from CDC, US census, and finds that opioid-related mortality is lower in counties with more cannabis dispensaries. The link existed for both recreational and medical dispensaries. Plus, a new analysis by Scientus Pharma and the University of Toronto showed that opioid prescribing declined more rapidly after legalization of recreational use in Canada. Interesting findings, but (as always with this type of study) correlation does not infer causation, and previous studies on the association between cannabis legalization and opioid deaths have shown mixed results.


Transcription trio. Jonathan Page and colleagues at the University of British Columbia and Fujian Agriculture and Forestry University have identified three new transcription factors involved in regulating the THCA synthase gene. A better understanding of the transcriptional control of the gene could help in future breeding efforts.


Spinal cord cannabinoid. Could medical cannabis help those suffering from essential tremor (involuntary shaking)? A University of Copenhagen team has shown (in a mouse model) that injection of a synthetic cannabinoid (WIN55,212-2) can reduce essential tremor by acting on spinal astroglial cannabinoid receptors. Next, the researchers plan to perform clinical tests on patients suffering from essential tremor to determine whether the new approach has the same effect on humans. Beyond that, “The cannabinoid might also have a beneficial effect on sclerosis and spinal cord injuries, for example, which also cause involuntary shaking," says research project lead Jean-François Perrier in a press release.


Stop swerving and start your stopwatch! Iain McGregor and the Lambert Initiative were in the news with a systematic and meta-analytic review into the magnitude and duration of (acute) Δ9-THC-induced driving and cognitive impairment. In short, THC does impair driving performance, but almost complete recovery is predicted within around seven hours of inhaling 20 mg. In a related press release, Iain said: “THC can be detected in the body weeks after cannabis consumption while it is clear that impairment lasts for a much shorter period of time. Our legal frameworks probably need to catch up with that and, as with alcohol, focus on the interval when users are more of a risk to themselves and others. Prosecution solely on the basis of the presence of THC in blood or saliva is manifestly unjust.” Iain and his team also graced the cover of The Cannabis Scientist in June (see Most Popular articles of 2021 below).


Doctor When. It’s 2021, you’re a family physician in Canada. Your patient is suffering from long-term pain. Medical cannabis has been legal for 20 years and you believe that it relieves chronic pain. Though the next step may seem straightforward, a qualitative study from McMaster University, Ontario, showed us that hesitation persists. On the basis of semi-structured questionnaires with 11 physicians, the researchers concluded that a lack of practical knowledge and concerns over potential harms were driving a reluctance to authorize the use of medical cannabis – despite the fact that all 11 physicians believed that medical cannabis can relieve chronic pain. Jason Busse, one of the study’s authors and associate director of the Michael G. DeGroote Centre for Medicinal Cannabis Research at McMaster said in a press release, "[...] more evidence, education and guidance is needed, so [family physicians] can better help patients who are asking about this treatment."


Go Fish. Using an “optogenetic platform,” University of Alberta researchers explored the effects of CBD and THC on zebrafish embryonic development. The detailed study measured the impact of both cannabinoids on neural activity (using a calcium-modulated photoactivatable ratiometric integrator – CaMPARI) as well as locomotive activity; CBD and THC both reduced neural and locomotive activity – especially at high doses, but CBD’s effects were greater. Most interestingly, when CBD and THC were administered together, the effects were greater still, indicating some sort of synergistic action. True, these are zebrafish and not humans, but it’s not hard to see a link between these results and the negative consequences of prenatal cannabis consumption.


Bigger and better. Proof that green fingers aren’t the only way of growing a good crop – researchers believe they have found the equation for precision breeding of scientifically based genotypes. After studying a diverse population of 121 genotypes of high-THC or balanced THC-CBD ratio, a positive association was observed between inflorescence productivity, plant height, and growth rate indicating that breeding for vigorous and fast-growing plants is likely to increase floral bud yield. The team also identified five parameters to successfully determine the final profile of stem diameter and plant height. To make the most of the reproductive potential of each strain, they suggest making cultivation adjustments with the plant’s unique growth pattern in mind. They hope their proposed prediction equation will facilitate the selection of prolific genotypes even without the completion of a full cultivation cycle.


Swimmers at risk. It doesn’t get more essential than this. Rumor has it that marijuana use is common among men presenting for fertility evaluation, and may have a detrimental effect on semen quality, particularly morphology and volume. But here’s the kicker: it may also be protective against abnormal sperm motility. So what’s a gal to believe? This daring evaluation took a closer look at this at-risk population by assessing the semen of 409 current, past, and “never-users.” Compared with never-users, current and past users had a significantly higher likelihood of abnormal sperm strict morphology (33.1% versus 50.7% and 53.4%, respectively; p < 0.001). However, sperm motility was more likely to be less than average in never-users than current and past-users (38.3% versus 21.1% and 27.2%, respectively; p = 0.01).


Chill pill. More and more people are turning to medicinal cannabis (MC) as a treatment for their anxiety and depressive disorders. But what effect does it have on condition symptoms, sleep, quality of life, and comorbid chronic pain? Participants who completed a baseline survey were invited to complete additional follow-up surveys at three-month intervals. The highlights? MC use was associated with lower self-reported depression but not anxiety. However, the MC group did report superior sleep, quality of life, and less pain on average.


​​Pain and conflict. Welcome to the latest instalment in the long-running Cannabis versus pain debate. Iain McGregor and colleagues reviewed the current landscape in the simply titled “Medicinal cannabis in the treatment of chronic pain” in the Australian Journal of General Practice (AJGP). Can you guess the main take-home message? Yes, you can: We need more research. “Despite the fact that current supportive evidence is of low overall quality, there are tens of thousands of patients with chronic pain being prescribed medicinal cannabis products in Australia, and hundreds of thousands using illicit cannabis products to self-medicate chronic pain,” write the authors. Evidently, the clear signal from society needs to be more thoroughly (and properly) investigated in the next wave of cannabis (and canninoid) clinical trials; can hundreds of thousands really be wrong?


Down in the delta (8 and 9).An online survey found participants compared delta-8 favorably with both delta-9-THC and pharmaceutical drugs, and reported substantial levels of substitution for both. Patterns of usage had both similarities and differences to delta-9 cannabis and products. Administration methods were primarily edibles (64 percent) and vaping concentrates (48 percent). About half of the participants (51 percent) used delta-8 to treat a range of health and medical conditions, primarily anxiety or panic attacks (69 percent), stress (52 percent), depression or bipolar disorder (46 percent), and chronic pain (41 percent).


No cannabinoid is an island. Adding to research around drug–drug interactions associated with cannabis use, scientists from Washington State University have looked at how cannabinoids might interfere with two enzyme families that help metabolize a range of prescription drugs. One study focused on major hepatic CYP450 enzymes, while the other looked at UDP-glucuronosyltransferase (UGT)enzymes. This is the first time there’s been a comprehensive study of the inhibition potential of the three most abundant cannabinoids – THC, CBD and CBN – on all major CYP enzymes. The results showed that these cannabinoids (and their metabolites) do in fact inhibit several P450 and UGT enzymes. In particular, this is the first paper to present evidence that the most abundant plasma metabolite, THC-COO-Gluc, inhibits CYP450 function, and that major kidney enzymes are also affected.

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About the Author
Lauren Robertson

By the time I finished my degree in Microbiology I had come to one conclusion – I did not want to work in a lab. Instead, I decided to move to the south of Spain to teach English. After two brilliant years, I realized that I missed science, and what I really enjoyed was communicating scientific ideas – whether that be to four-year-olds or mature professionals. On returning to England I landed a role in science writing and found it combined my passions perfectly. Now at Texere, I get to hone these skills every day by writing about the latest research in an exciting, creative way.

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