Leading experts have questioned the legitimacy of a new study, which appears to link cannabis to cancer, saying medical consumers don’t need to be concerned.
A recent study has claimed to show “strong” evidence that both THC and CBD – active ingredients in cannabis – are associated with the formation of multiple cancers.
Researchers at the University of Western Australia called the results “very concerning” and have concluded that use of cannabis should be urgently restricted worldwide.
But proponents of medical cannabis are sceptical of the report and have spoken out to Cannabis Health about their concerns as to the legitimacy of the research.
They have dubbed it “obscure science” with missing information which counters other studies and say it can be dismissed as “scaremongering”.
The findings of the study, which was conducted at the Division of Psychiatry, University of Western Australia, were published on 30 March.
The researchers used statistical software to access the census rates of 28 cancer types in all US states from 2001 to 2017 from the National Cancer Institute.They then accessed drug exposure information from the National Survey of Drug Use and Health 2003 to 2017.
Federal seizure data from the US Government provided details of cannabinoid exposure.
A total of 19,877 age-standardised cancer rates were returned.
From the results they found that 15 cancers were more prevalent than usual in those who were exposed to high levels of CBD, the report said.
The researchers said the results were particularly concerning as more people across the globe are being exposed to cannabinoids.
It concluded that public access to cannabinoids should be carefully restricted “as a matter of public health and safety” and to retain the integrity of the food chain.
Doing this is a “non-negotiable” investment in the genomic health and prevention of cancers of multiple coming generations, the researchers stressed.
Discounting the report
Professor Mike Barnes, consultant neurologist and medical cannabis expert, told Cannabis Health that the report is “very obscure science” and makes little sense.
“Frankly, I doubt this study and would be very cautious at accepting it at face value,” he said.
Most of the studies he is aware of have noted the anti-cancer properties of various cannabinoids and cannabis is often prescribed for cancer symptoms.
“This [report] is counter to that and implies cannabis can exacerbate cancer.”
Professor Barnes noted specifically that the data came from federal seizures, which makes it difficult to know exactly what the cannabis contains, such as contaminants like pesticides or mould.
The dose is unknown, as is whether the cannabis is synthetic or full spectrum.
“I think I would ignore this as it is potentially scaremongering for no good reason,” he added.
“All the evidence so far is that cannabinoids including CBD and THC are anti-cancer and not pro-cancer.”
Dr Simon Erridge, head of research and access at Sapphire Medical Clinics, dug further into the report, concluding that he does not see any cause for concern.
“This is an interesting study which attempts to ask some interesting questions with respect to cancer risk related to exposure in the general population,” he told Cannabis Health.
“Whilst I commend the authors for their attempt to answer this question there are some key limitations to their analysis.”
The study is more representative of exposure to illicitly obtained cannabis through the black market where analysis of cannabinoid concentrations is from federally seized cannabis, rather than that sourced through dispensaries.
“As we are aware, illicitly obtained cannabis is more likely to be smoked, rather than administered via any other method,” he continued.
“We know that if you consume cannabis by smoking this causes the production of cancer-causing compounds in the same way as smoking tobacco and therefore it is not a recommended method of administration for medical cannabis.”
Administration of medical cannabis flower via vaporisation heats the cannabis flower to a lower temperature without igniting it.
This has been shown to significantly reduce the associated concentration of harmful chemicals produced, and is therefore the prescribed method of administration.
Dr Erridge’s major concern, he said, is that the study authors conclude that there are associations between some cancer types and cannabis, and specific concentrations of cannabinoids.
“However, the correlations as detailed in their analysis are weak and their analyses find almost as many incidences whereby higher cannabis and/or cannabinoid consumption is associated with a lower incidence of cancer, but they do not highlight this in this text,” he explained.
“The findings from their statistical tests therefore seem to be a result of having a high number of observations, leading to false positives with respect to both findings.”
Finally, there are large disparities between the types of cancer which are associated with cannabis and THC, he said.
Dr Erridge adds: “This is suspicious as one of the figures shows that THC is the cannabinoid which is prevalent in the highest proportions.”
Senior research fellow Dr Wai Liu of St George’s, University of London – who has been researching the anti-cancer properties of cannabis for most of his career – said the report is to be approached with some caution.
There is a lot of data contained within it, some of which seemed perplexing, he said.
For example, the study suggests that there is an inverse correlation between the consumption of alcohol and cancer of the liver ; which means the “more you drink, the less chance you have of getting liver cancer” – a finding he describes as “bizarre”.
“It’s the complete opposite of what I know to be the case from studies from the Cancer Research Institute, for instance,” he told Cannabis Health.
“All evidence shows a positive link between alcohol and cancer of the liver, but this paper is showing the complete opposite.
“We also don’t know what population they are looking at, so it’s such a mixed bag that it makes things very unclear.”
The paper also singles out CBD, but fails to state what amount of the cannabinoid was consumed.
“It’s all based on cannabis but they’re not sure what the percentages are of each cannabinoid, so it’s very messy and it’s not conclusive. I don’t think they can say CBD causes cancer because it’s CBD mixed with other things, such as THC and tobacco.”
Dr Liu has conducted several studies in cell and animal models and while not scientifically proven as a cure, he confirmed that cannabinoids “definitely have anti-cancer properties”.
He has heard hundreds of testimonies from patients who have benefited from using CBD while waiting for or alongside conventional cancer treatment, but he warns that papers such as this have led to patients stopping using CBD altogether.
“I’ve had patients bring this study to me and express concerns about its findings. Studies like this should come with a caveat making it clear that it isn’t looking at the cannabinoids individually but rather everything is lumped in together,” he added.
“Sometimes studies can be portrayed as clear and definitive – this is not the case here. I’d rather researchers say this and stress the limitations rather than present it as a complete scientific report.”
According to Cancer Research UK, scientific research studies on the use of cannabis for cancer patients have had mixed results.
Some show that cannabinoids can cause cell death, block cell growth, stop the development of blood vessels needed for tumours to grow, reduce inflammation and reduce the ability of cancers to spread.
Meanwhile, scientists have also discovered that cannabinoids can sometimes encourage cancer cells to grow or cause damage to blood vessels.
“We need more research to know if cannabis or the chemicals in it can treat cancer,” the Cancer Research UK website reads.
“Clinical trials need to be done in large numbers where some patients have the drug and some don’t. Then you can compare how well the treatment works.
“Many of the studies done so far have been small and in the laboratory. There have been a few studies involving people with cancer.”
How THC and CBD work together in the brain – new study
New findings on how CBD and THC – the psychoactive compound in cannabis – affect the brain when administered together, could help to develop new cannabinoid therapeutics, scientists say.
A study has investigated the impact on the brain of CBD and THC, both as separate entities and when co-administered.
Researchers at University College London (UCL) analysed data from previous studies, including one which used functional Magnetic Resonance Imaging (fMRI) technology to measure brain activity in participants taking CBD and THC.
For the first time, they explored the response of the striatum region of the brain – a major part of the motor and reward systems. This is a critical component of numerous aspects of cognition, including motor and action planning, decision-making and motivation.
One study compared inhaled cannabis containing 8 mg THC, 8 mg THC + 10 mg CBD and a placebo. It showed strong disruptive effects of both THC and THC + CBD on connectivity in the associative and sensorimotor networks.
However it also identified a “specific effect of THC” in the limbic striatum network which was not present in the THC + CBD condition.
In a second study, testing oral 600 mg CBD versus placebo, CBD increased connectivity in the associative network, but produced only relatively minor disruptions in the limbic and sensorimotor networks.
The study concludes that THC “strongly disrupts striato-cortical networks” but that this effect is mitigated by the co-administration of CBD.
It states: “Oral CBD administered has a more complex effect profile of relative increases and decreases in connectivity.
“The insula [part of the brain implemented in diverse functions including emotions and self-awareness] emerges as a key region affected by cannabinoid-induced changes in functional connectivity, with potential implications for understanding cannabis-related disorders, and the development of cannabinoid therapeutics.”
This is the first report in human subjects of data from THC, THC + CBD and CBD use achieved “using a unified set of analysis methods, and with all comparisons performed in a placebo-controlled, double-blind design”.
Read the full report here.
Five new cannabis studies to have on your radar
The latest scientific papers exploring cannabis and its impact on health and society.
Get up to date with the latest cannabis-related research from across the globe.
Over the past few weeks, we’ve seen papers published around inaccurate labelling, the effects of cannabis on Covid-19, the impact of legalisation in Uruguay and how cannabis users might require more sedation during medical procedures.
Read on for five significant studies to dive into.
Lower Covid-19 severity among cannabis users
The researchers aimed to assess whether current cannabis users hospitalised for Covid-19 had different outcomes compared to non-users through a retrospective analysis of 1,831 patients admitted to UCLA Medical Centre in California.
Analysis of the data found that cannabis users had significantly better outcomes compared to non-users, shorter hospitalisation, lower ICU admission rates and less need for mechanical ventilation.
Interestingly, the researchers also found that active users had lower levels of inflammatory markers upon admission than non-users.
The authors of the study concluded: “This retrospective cohort study suggests that active marijuana users hospitalised with COVID-19 had better clinical outcomes compared with non-users. However, our results need to be interpreted with caution given the limitations of a retrospective analysis.
“Prospective and observational studies will better help elucidate the effects of marijuana use in COVID-19 patients.”
Cannabis users require more sedation for endoscopy
According to new research, patients who use cannabis required higher levels of sedation during gastric endoscopies than non-users.
As cannabis is legalised in more places and usage continues to rise, researchers in Canada said clinicians should be aware of patients’ cannabis consumption and prepare themselves for increased sedation and the risks that come with it.
The authors of the study conducted a prospective cohort study of 419 adult outpatients undergoing endoscopic procedures at three Canadian centres. Procedures were conducted under conscious sedation, which leaves the patient relaxed and comfortable but partially conscious during the procedure.
Cannabis use was associated with increased odds of requiring higher total sedation during gastroscopy, an endoscopic procedure that begins with the insertion of a tube and camera through the throat.
Legalisation not associated with increased cannabis use among young people
A recent study from researchers in Uruguay found that the use of cannabis following legalisation decreased among teenagers.
Uruguay was the first country in the world to legalise and regulate recreational cannabis. Since legalising the drug in 2016, the country is now regarded as a pioneer, paving the way for other countries like Canada, Mexico and Malta.
Using data from cross-sectional surveys of secondary students in Uruguay and Chile, the study evaluated changes in the prevalence of past-year, past-month and any risky and frequent cannabis use following the enactment and implementation of cannabis legalisation
“The legalisation of recreational cannabis in Uruguay was not associated with overall increases in either past-year/past-month cannabis use or with multi-year changes in any risky and frequent cannabis use among young people,” the authors stated in the paper’s abstract.
Current cannabis labelling system “doesn’t tell you much”
Labels like indica, sativa and hybrid—commonly used to distinguish one category of cannabis from another—tell consumers little about what’s in their product and could be confusing or misleading, suggests a new study of nearly 90,000 samples across six states in America.
Published on 19 May in the journal PLOS One, the research constitutes the largest analysis to date of the chemical composition of cannabis products.
It finds that commercial labels “do not consistently align with the observed chemical diversity” of the product. The authors are now calling for a “weed labelling system” akin to the Food and Drug Administration’s “nutrition facts panel” for food.
“Our findings suggest that the prevailing labelling system is not an effective or safe way to provide information about these products,” said co-author Brian Keegan, an assistant professor of Information Science at CU Boulder.
“This is a real challenge for an industry that is trying to professionalise itself.”
Cannabis dependence treatment is effective in tackling common co-morbidities
Earlier this month, Australian researchers released a paper looking into the effectiveness of cannabis dependency treatment on common co-morbidities, including mood, sleep and pain problems.
The researchers found that the treatment helped decrease anxiety, stress and sleep disturbance among the cohort of 128 cannabis-dependent participants.
The analysis used data from a 12-week double-blind placebo-controlled trial testing the effectiveness of the cannabis-based medicine nabiximols against placebo in reducing illicit cannabis use.
The researchers found that there was “no evidence” that nabiximols treatment is a barrier to reducing co-morbid symptoms. In fact, they found that the treatment reduced illicit cannabis use and improved comorbidity symptoms, even when participants were not able to achieve abstinence.
Research finds cannabis consumers may require more sedation
Consumers required higher levels of sedation during endoscopic procedures than non-users
Experts have highlighted the need for doctors to be more aware of their patients cannabis use, as research suggests consumers may require higher levels of sedation.
As cannabis is legalised in more places and usage continues to rise, researchers in Canada said clinicians should be aware of patients’ cannabis consumption, and prepare themselves for increased sedation and the risks that come with it.
It comes as a new study has associated cannabinoid use with increased odds of requiring higher total sedation during gastric endoscopies – a procedure that begins with the insertion of a tube and camera through the throat – than non-users.
The authors of the study conducted a prospective cohort study of 419 adult outpatients undergoing endoscopic procedures at three Canadian centres.
Procedures were conducted under conscious sedation, which leaves the patient relaxed and comfortable but partially conscious during the procedure.
“Patients didn’t have increased awareness or discomfort during procedures, but they did require more drugs,” said Yasmin Nasser, MD, PhD, lead researcher on the study and assistant professor at Snyder Institute for Chronic Diseases at the University of Calgary.
Each patient completed two questionnaires, one before the procedure about their cannabis use and another afterwards, indicating their awareness and comfort level during the procedure. The questionnaires were analysed along with details about the use of the sedatives midazolam, fentanyl and diphenhydramine during the procedure.
Cannabis use was associated with increased odds of requiring higher total sedation—defined as more than 5 mg of midazolam, or more than 100 mcg of fentanyl, or the need for diphenhydramine.
Interestingly, cannabis use was not associated with higher use of sedation during colonoscopy. Researchers said this could be because gastroscopy generally requires more sedation than colonoscopy due to the irritation caused in the upper part of the gastrointestinal tract.
Cannabinoid use was not independently associated with fentanyl use or adverse events, nor was it associated with intra-procedural awareness or discomfort, the authors found.
This study looked at whether patients were users or non-users of cannabis, but did not examine the timing, quantity or route of cannabis intake prior to the procedure. Researchers say these variables could be the basis for future studies.
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