Last updated on September 14th, 2020 at 12:04 pm
Editor’s note–this article has been updated and included into a multi-part series on marijuana and medicine. Check it out there.
As the push to legalize marijuana for personal or medical use gains traction in the USA, the “pro-pot” arguments become more enthusiastic and more off the beaten track of real science. I suspect, like legal same sex marriage, social norms have changed, and legal marijuana is something that will become commonplace across the country, except in some deeply conservative areas. The Federal Government has shown little enthusiasm in enforcing Federal law, which retains the highest authority in regulating certain drugs, in states that allow legal marijuana.
I personally have no issue with smoking marijuana, since other “drugs”, like alcohol, are completely legal and socially acceptable. I think that legalizing marijuana will reduce much of drug trafficking, reduce the burden of law enforcement and penal system costs, and have other beneficial effects to society.
I still want regulations such as control over public smoking (I don’t want second hand cannabis smoke wafting over me or my children, as much as I don’t want to inhale other people’s tobacco smoke), there needs to be regulations about when it might be illegal to be high (I don’t want my Delta Airlines pilot to be smoking weed before flying my jet, and I don’t want automobile drivers to be under the influence), and I want age regulations no different than there is for alcohol and cigarettes (despite . But I think those are reasonable boundaries for legalization of cannabis that would be reasonable to most people. But this isn’t the point of this article.
What troubles me about the “debate” about legalization of cannabis is that the pro-pot side seems to make claims about various medical benefits that appear to be only tenuously supported by real scientific evidence–in fact, some of the claims are downright dangerous. The reasons for doing this is probably, though I can only speculate, to make it appear that marijuana is some miracle product, so let’s speed up the legalization of it. It’s like the Food Babe telling us that kale is the miracle food, except that kale isn’t illegal. It does taste awful (but not the point).
On the internet, you will find numerous memes, blog posts, and even mainstream articles that claim that smoking pot, eating pot, rubbing hemp oil (which is manufactured from the seeds of Cannabis plants that don’t contain much THC, or tetrahydrocannabinol, the active hallucinogenic agent of cannabis), or doing something with all or a part of a cannabis plant will cure or prevent some disease, mostly, but not exclusively, cancers.
Famously, marijuana has been used as an anti-emitic to ameliorate or mitigate nausea and vomiting after radiotherapy and chemotherapy in cancer treatment. In fact, marijuana has been smuggled into some cancer wards since the late 1930’s. Unfortunately, even with this particular use of the drug, there have been negative results in some well designed clinical trials and positive results in some others. The highly variable result may result from difficult trial design to bias to a huge dose of the placebo effect, an effect that many scientists have concluded is overrated.
But even as an anti-emitic, marijuana has no curative power, it’s a palliative treatment for the nasty side effects of chemotherapy and radiotherapy in the treatment of cancer. Since weight loss and wasting are side-effects of cancer treatments, any medication that can prevent the nausea and vomiting can lead to better medical and lifestyle outcomes in cancer treatment. If there is a real clinical difference between those who use marijuana vs. those who don’t for cancer therapy effects, we need real clinical trials that show the difference. Moreover, to do this type of clinical research correctly we require real dosage information, that is, at what dose do we get the best effect. This would be a landmark study, and until then, all we have are anecdotes, albeit emotional ones.
Is there any evidence out there that actual cannabis or its byproducts have any effect on cancers or neurological conditions? Before we start, let’s remember that there are 100 to over 200 different types of cancer (the actual number depends on how some researchers subdivide some cancer types) in humans. And each of these different cancers have different pathophysiologies, different genetics, different prognoses, different causes, and different treatments. In other words, it is not one singular disease which might someday have one unified course of treatment.
If I could make a recommendation, always be skeptical when someone makes some claim that “XYZ cures or prevents cancer”, because that’s going to be nearly impossible. Every cancer is so different with such different physiology, there is just never going to be a magic pill. And if a cancer has become metastatic, there is simply no way one treatment can work.
And preventing cancer becomes more problematic. It usually takes numerous, up to 10, independent mutations of a cell before it can become a growing, metastatic cancer. Each mutation is selected, as in natural selection, because it provides some benefit to the cancer cell, such as causing blood vessels to supply the cells for nutrition and oxygen, or the ability to divide rapidly, whatever the feature is. They aren’t “naturally” a part of the cell, but caused by a mutation. And these mutations are more or less random, and they can’t be prevented by anything special. You can’t down 500 Vitamin C tablets and expect it to block these rare mutations.
So before I head down the the road of whether THC or cannabis has any effect on any particular disease, I’m not going to play the argument from ignorance. If there isn’t any evidence that marijuana or THC cures a particular cancer (or any disease), then that means there’s no evidence.
I don’t have evidence there’s a pink unicorn walking on Mars, but I’m fairly certain of it. So don’t say “no one has never researched smoking weed on reduced brain cancer, so you don’t know if it does.” Nope, I don’t do those kind of arguments. If there is no evidence that smoking cannabis cures brain cancer, we cannot claim that it cures brain cancer. If I am certain that unicorns don’t exist, and that they’re are no pink versions of unicorns, and that there’s not enough atmosphere on Mars to allow the survival of unicorns, then we have enough biological plausibility (or lack thereof) to state that there are no pink unicorns on Mars. Of course, someone will then state that there’s a secret cavern that has is filled with oxygen and organic, GMO-free foods for a hidden population of pink unicorns. There’s no winning when it comes to the argument from ignorance.
The first step I take before I investigate any internet claim is to examine the quality of the evidence supporting the claim. Mostly, I want to find systematic reviews of clinical research to give me the best possible evidence of whether a potential therapy has actual clinical usefulness. A search of the Cochrane Reviews, which can be a useful tool in finding a scientific consensus in a new therapy, shows not one systematic review of THC or cannabis in cancer therapy, although there are some that look at mental disorders (which is still important). There are numerous reasons why Cochrane may not have a review about a procedure or drug, mainly because there just aren’t enough clinical studies of high enough quality to roll up into a systematic review. That’s a clue, but it’s more a lack of evidence rather they are overwhelmed by solid evidence.
Let’s see what’s going on recently. Remember, if some article was published 10 years ago, and there’s not one single follow-up study, it’s dead on the vine, meaning that no one was able to repeat the data. No one was able to move it from some cell-culture or animal model to a human clinical trial. This happens all of the time, because failure in oncology drugs is the norm. Remember, if you find a study published in 1995, and it’s never cited or never repeated, that’s probably because it couldn’t be repeated. That’s how science works.
First, we should review some of the better studies in marijuana research on cancer. A couple of points: first, most of the research is primary, and has yet to be repeated widely, and second, there is little or no clinical evidence which can be used in systematic reviews of cannabis, which would form the basis of evidence based medicine of using cannabis in a clinical setting.
- Breast cancer. A recent review of the relevant research regarding the use of cannabinoids (the essential active compounds of marijuana) in the war on breast cancer concludes that “our current knowledge on the anti-tumor potential of cannabinoids in breast cancer, which suggests that cannabinoid-based medicines may be useful for the treatment of most breast tumor subtypes.” All of this research is based on rodent studies, and the joke in scientific research circles is that we’ve cured cancer in mice for decades. It’s important to understand that only a tiny percentage of therapeutic cancer drugs make it from an animal study clinical trial (about 5%), and even then, only about less than 8% (pdf) of oncology drugs that enter clinical trials actually end up being approved for use in humans. In other words, there’s only a 0.4% chance of any drug that’s being tested on cells or mice is ever going to end up being approved for human use. There is no nefarious conspiracy going on to block these drugs, it’s that in clinical trials the vast majority of these compounds fail to show effectiveness beyond their safety issues. And in cancer therapy, sometimes drugs that have a 51:49 benefit to risk ratio, and only keep a person alive for a few months get approved. So, the ones that don’t make are remarkably ineffective or unsafe. There is just no evidence that cannabis will treat or prevent breast cancer in humans. None. But let’s hope that it will fall in the 0.4% category.
- Breast cancer. Again. Let’s say that we actually can gather evidence that marijuana has an effect on breast cancer. First, we need to determine how much THC actually would kill most breast cancer cells. In one study, the researchers determined that it would take a concentration of cannabinoids of approximately 10 µmol/L to cause the death breast cancer cells in cell culture. This converts to around 3.14mg/L of THC. So, you’d have to assume that to kill any breast cancer cells, you’d need at least a blood level of 3.14 mg/L to achieve breast cancer cell death. So how close to that 3.14 mg/L can we get by just smoking a joint or two? According to research, smoking one joint will give you a blood level of THC of around 1.3-6.4 ng/mL serum, or about .00013-.00064 mg/L. In other words, to get an anti-cancer effect, you need to light up around 1000 joints per day. Yes every single day until every single breast cancer cell would die. Of course, your lungs couldn’t tolerate that, nor probably your ability to function in any “normal” manner. Of course, you could consume this in other ways, for example ingesting it, but again, you’d need to eat more than 1000 joints (because less digestion is less efficient in absorbing THC than the lungs, which is why it is smoked). And these levels may be more generally toxic to body, in effect killing you. If we ever uncover clinical evidence that marijuana “cures” breast cancer, Big Pharma will spend the money researching which molecule is actually responsible, the over all toxic dose, the amount necessary to kill the cancer cells, and how to deliver it. And then they will patent it, because they did all the hard work, and they will get $10,000 a dose (just a guess). So, let’s be clear. Smoking a couple of joints is NOT going to cure your breast cancer.
- Colon cancer. In a recent article, researchers examined the effect of cannabidiol, a non-psychotropic ingredient of cannabis, on chemically induced cancerous colon cells in cell culture. The authors concluded that it could prevent colon cancer. Now, if I was harsh about mouse research as being an indicator of clinical success, I’d be harsher about cell cultures. This was tested on chemically induced colon cancers, which may or may not have the same pathophysiology of in situ colon carcinomas. And once again, we lack any clinical evidence that it might work in humans, but I guess this is another bet into the 0.4% chance column.
- Glioma. Junk medicine hawkers have been pushing hash oil to “cure” gliomas, a type of malignant brain and central nervous system cancer. It is based upon some preliminary research on just 9 patients in Spain. Only two of the patients survived more than a year, while the seven others had a course of the disease not different than what is experienced in typical treatments of gliomas. In fact, in the two patients who survived the longest (yet still died), the effect can be attributable to spontaneous (but temporary) regression of the disease, a fairly common event. In a review of these studies and claims, the author stated, “I didn’t find anything I would call “earth-shattering” or even anything that could be considered credible evidence that hash oil can cure advanced gliomas.” At this point, there is no supporting evidence that hash oil should be considered the first, second, third, or fourth line of treatment for gliomas. Right now, we have observations (which are just barely above anecdotes on the scale of scientific evidence) that hash oil might work. And maybe those observations can be used to create an hypothesis which can be tested in a controlled clinical trial. But until that point, there is no evidence that hash oil works to treat glioma. None.
- Lung cancer. In this case, it’s not about whether cannabis can treat lung cancer, but whether it actually causes it. In a recent retrospective epidemiological study, the authors stated, “in conclusion, the results of the present study indicate that long-term cannabis use increases the risk of lung cancer in young adults.” There is a “belief” that smoking pot is less problematic than smoking other types of plant material, such as tobacco. That is a false assertion, because the reason why smoking is so tied to lung cancer is that the epithelial lining of the lung is susceptible to carcinogens; moreover, as the authors state, part of gaining effects of the pot is to inhale deeply and hold the smoke in the lungs for a greater period of time than in cigarettes (and certain cigars), it might actually increase the exposure of lung cells to the smoke and any associated carcinogens. To be fair, the evidence is conflicting, but even in one large study that shows no conclusive evidence that there is an increased risk of lung cancer in non-cigarette smoking individuals, there appears to be increased risks for some types of cancer amongst marijuana smokers, including prostate cancer.
- Clinical trials involving cannabis and cancer. There are currently 8000 clinical trials that are recruiting patients for anti-cancer drugs (and over 19000 that are closed to patients), and as far as I can tell, there are none registered for marijuana, or isolated cannibinoids, dronabinol and nabilone. On the clinicaltrials.gov website, which tracks every clinical trial registered across the world (and in case you’re going to ask, no one would have a real clinical trial and not register it, since it shows you have regulatory approval to begin a trial), there is precisely one cannibinoid being used to treat cancer, and that is Sativex, which is a patented drug of nabixomols isolated from the marijuana plant. This study is just a Phase 1 trial, it hasn’t recruited any patients, and is years from providing us with any meaningful results. There might appear to be a lot of research into cannabis using cell culture and animal models, but none have been transferred over to human clinical trials. This is not unusual, because even though it seems that there is a lot of research into cannabis and cancer, the total mass of research into other compounds with respect to cancer is substantially larger, because the evidence for both mechanisms of the treatment and clinical successes for these other products are much higher. Look at it this way–there are currently over . Cannabis research is a tiny speck (though not an insignificant speck) of the cancer research world, compared to the vast body of research currently ongoing. Cancer research isn’t randomly throwing compounds at cells and seeing if they work or not, it’s a logical process to determine if a compound has a reasonable chance of inhibiting some part of the cancer growth or development. There is some potential for cannabis, but it probably doesn’t compare to what is currently in the 27,000 compounds in current clinical research, and, in a business sense, the return on investment for researching compounds that have better understood pharmacologic mechanisms of action on cancer are higher.
Dementia. As I’ve said before, the nearly gold standard of medical research is the Cochrane Reviews (they are great, but not perfect), so I looked there for systematic reviews that roll up the data from many clinical trials. And in this case, Cochrane concluded that cannabis doesn’t help. The authors concluded that “this review finds no evidence that cannabinoids are effective in the improvement of disturbed behaviour in dementia or in the treatment of other symptoms of dementia.”
Epilepsy. Another Cochrane Review examined the effect of smoking cannabis on epilepsy (an anecdote shared by Dr. Gupta). The authors found “no reliable conclusions can be drawn at present regarding the efficacy of cannabinoids as a treatment for epilepsy.” This means what it means, that a thorough systematic review of clinical research currently available on marijuana’s effects on epilepsy has shown nothing. Sure, maybe better trials will show it’s quite efficacious, but remember, that doesn’t mean it will be so. And physicians treating epilepsy need to stick with evidence based medicine.
In a recent systematic review published in Neurology, the effect of marijuana was analyzed with respect to several neurological disorders and conditions. They included 34 clinical studies since 1948 (an extremely small number, because there just so few clinical studies), and looked at three different forms of cannabinoids–oral, THC, and synthetic. Here are their conclusions:
- Spasticity, or chronic spasms of large muscles. All three forms showed some reduction in spasticity, though THC may take longer than a year to improve the condition.
- Treatment of pain in multiple sclerosis. Most forms show a positive clinical effect, but THC probably has no effect.
- Treatment of bladder dysfunction in multiple sclerosis. Nabiximols, a synthetic cannabinoid, seemed to work. The other forms of cannabis had no effect.
- Treatment of tremors in multiple sclerosis. In this case, nabiximols have no effect, but other forms do.
- Treatment of involuntary movements. Ineffective for Parkinson’s disease, and insufficient data for other forms, such as Tourette’s Syndrome.
- Decrease seizures in epilepsy. There was insufficient data to support or refute its use, although the Cochrane Review above says about the same thing in a different way.
- Despite the incredibly small number of patients included in all of these trials, the authors found that more patients stopped using THC because of adverse effects (6.9%) vs placebo (2.2%). Such a large dropout can bias the results of primary clinical trials and systematic reviews.
- The placebo effect (reported to be as high as 70%) is a major impediment to determining whether cannabis has any effect on these neurological conditions. If there’s nothing more than a placebo effect, which is really no effect whatsoever, then the numerous, albeit minor, adverse events outweigh the benefits, and it should not be added to body of literature regarding evidence based medicine.
I have heard the Strawman Arguments that Big Pharma, the FDA, the National Cancer Institute (if the cannabis supporters know it exists), and the US Government suppress all the research that show how great cannabis is for cancer and other clinical indications because those groups don’t want pot to be legal. As amusing as that argument might be (and it’s a fairly bad one), if cannabis or any of its components actually could show efficacy against any of the 200 or so cancers, Big Pharma would be all over it. Because, they would not be selling joints, they would be isolating the active ingredient, defining the exact dose, determining how to deliver it to the local cancer site in the body, funding clinical trials, filing documentation with the FDA, then getting it into physician’s hands. This is not an easy process, but it would be a profitable one if it worked. Big Pharma and the National Cancer Institute are looking at everything, and they ignore nothing for potential in treating cancers. If cannabis works (and it might), they are all over it. Big Pharma is providing a lot of the funding for it.
Risks of smoking marijuana
There are known risks to individuals who smoke marijuana. This is uniformly ignored by everyone, and there are even false claims that somehow smoking cannabis is safer than smoking other plants, like cigarettes. Part of the belief lies in the Appeal to Nature fallacy, which, in this case, implies that somehow marijuana is purer and healthier. The environmental damage from the poisons used to grow marijuana (which will, in fact, remain on the plant, and make up part of the what is inhaled) are legendary.
One of the reasons tobacco smoking is dangerous is that the epithelial cells in the lung, which make up a huge surface area of cells, are extraordinarily sensitive to environmental damages like air pollution and smoking. Though there is some evidence that marijuana smoking is less carcinogenic than tobacco, and in fact has components that have the opposite effects than tobacco smoke. But that shouldn’t be read that marijuana smoke has no carcinogenic properties, it is just less than cigarettes.
There’s also some recent evidence, published in a high impact factor journal, Human Reproduction, which found nearly double the risk of poor sperm morphology (with the possible result of infertility) after smoking marijuana (while cigarette smoking, type of underwear, and other myths about male fertility were shown to be irrelevant).
On the other hand, marijuana smoke deposits 4X as much tar in the lungs as do cigarettes. Although this may not be carcinogenic, tar can lead to the same non-cancer long-term damage to the lungs as do tobacco products–emphysema, bronchitis and lung infections. In other words, if we’re looking at marijuana as a medical product, it’s risks are known and real. If I were a medical researcher (oh wait….), and if marijuana had a real value medically (say it did cure breast cancer), smoking it would be the worst possible way to deliver the drug to the body. As I mentioned above, I would isolate the compound in marijuana that actually killed breast cancer cells, figure out a way to carry that molecule to the target site at the appropriate dose, and avoid harming the lungs. That’s how a real medical product works.
The New York Times reported that New York State had started the legislative process “to join 22 states in legalizing medical marijuana for patients with a diverse array of debilitating ailments, encompassing epilepsy and cancer, Crohn’s disease and Parkinson’s.” Even though New York eventually legalized it, the the New York Times shared their concerns about medical marijuana:
…yet there is no rigorous scientific evidence that marijuana effectively treats the symptoms of many of the illnesses for which states have authorized its use. Instead, experts say, lawmakers and the authors of public referendums have acted largely on the basis of animal studies and heart-wrenching anecdotes. The results have sometimes confounded doctors and researchers.
So, does marijuana work to prevent or cure cancer? There is little evidence that it prevents cancer and a little evidence that it can cure cancer. But these are very limited in vivo and animal studies, very preliminary and not in controlled clinical trials. Just to give a little perspective, less than 8% (pdf) of oncology drugs that enter clinical trials actually end up being approved for use in humans. The failure rate is rather large because the efficacy is generally measured in small amounts for many types of cancers.
For neurological disorders, there are some, but not broad, indicators that THC or its derivatives, could have benefits. But, it’s clouded by the extremely small size of clinical trials, a large potential placebo effect, bad trial design, and different kinds of bias. The systematic reviews tend to heavily qualify their conclusions, mainly because of the lack of large, gold-standard, clinical trials. In other words, there isn’t enough, at this time, for a neurologist to say “this will help.” We don’t know. Which, again, does not mean you can proclaim that if we don’t know, the we do know.
Dr David Gorski, a real oncology researcher, whose knowledge and expertise in these areas matter quite a bit, reviewed the research in many of the medical claims about marijuana and concluded that,
There’s no doubt that what is driving the legalization of medical marijuana in so many states has far more to do with politics than with science. Right now, for all but a handful of conditions, the evidence is slim to nonexistent that cannabis has any use as a medicine, and those conditions, such as CINV and chronic pain, can often be treated more reliably with purified or synthesized active components. Moreover, for one condition for which there is reasonably good evidence for the efficacy of cannabis and/or cannabinoids, namely chronic pain, politicians are reluctant to approve medical marijuana.
This is the same thing with a lot of science in this country. Political expediency trumps real scientific research. Anthropogenic global warming, which is backed by a wealth of evidence, is rejected because it’s a “liberal conspiracy” or some such nonsense. Well, now politicians want to allow marijuana because of medical benefits, almost all of which are unsupported by real scientific evidence, while ignoring some of the known risks of smoking the drug. If politicians want to make marijuana legal, do so because it’s a recreational drug, not unlike alcohol.
The world of medical marijuana is using the same weak evidence, the same ignorance of risks, and the same logical fallacies you hear from those who push “natural” herbs or supplements. And the more we look the more we find that there’s nothing there. We need to separate recreational use of marijuana from medical use. They are not the same, and one shouldn’t support the other.
The TL;DR version
- Marijuana prevents nausea in cancer treatment patients–maybe, maybe not. No solid research in the area.
- Marijuana cures cancer–no clinical evidence that it does.
- Marijuana can treat neurological conditions–not really, but some isolated cannabinoids may help ameliorate some symptoms of some conditions.
- Marijuana has some risks that have not been fully explored. But stay tuned, I have more to write on this.
- There is no global Big Pharma conspiracy to suppress clinical research on marijuana. If it could “cure” one cancer, they’d be all over it trying to find the right dose, delivery mechanism, and pretty advertising to make billions of dollars.
If you want to smoke marijuana (or eat it in a brownie–not sure that’s a thing anymore, it was when I was in college) because it’s relaxing, or you need to blow off steam after a tough day, fine. Go for it. I absolutely do not understand why this usage is illegal. It’s costly to society. And banning it provides no benefit to society.
On the other hand, I find most, if not all, of the medical claims made about marijuana to be laughable. The evidence is just so weak or non-existent, I actually have no clue why it’s part of the discourse, but then again people deny evolution, and we end up arguing that. Yes, there are bits and pieces of intriguing evidence that a component of marijuana may have some benefits to human health. But we’re a long ways from testing that with real clinical trials, then getting it to market. And trust me, when someday we have found some real clinically significant uses, it’s not going to be sold as a “joint.” It’s going to be developed into some sort of medical delivery formulation (like a pill or injectable solution) that gets the purified pharmacologically relevant compound to the physiological site where it would work. That’s how real medical science works.
- I have a policy of open commenting and dissent to my articles. I only delete spam, racism, and just random nonsense. Please comment here if you wish, because I know everyone has an opinion on pot. You can say that I’m full of equine manure, but you better have peer-reviewed evidence.
- There is a US Patent that has, as one of its statements, “This invention relates to the use of phytocannabinoids, either in an isolated form or in the form of a botanical drug substance (BDS), as a prophylactic or in the treatment of cancer.” There are memes that state that Big Pharma knows that cannabinoids cure cancer or else they wouldn’t have patented it. However, patents do not represent peer-reviewed science, and merely conjecture on the part of the patent holder, so that they may potentially block anyone from manufacturing the drug for the use that it claims. There is no evidence that this cannabinoid has any real potential of doing anything until such time that there are randomized clinical trials that support these claims. So, don’t mention patents. They mean absolutely nothing, because drug companies continuously file patents when they even think something might do something. Most drug patents never end up being drugs.
- Let me remind you that the quality of the source used matters, and cherry picking primary studies to support a Confirmation Bias is not not how real skepticism works. Remember, if some article was published 10 years ago, and there’s not one single follow-up study, it’s dead on the vine, meaning that no one was able to repeat the data.
- Do not accuse me of cherry-picking. There are lots of published articles out there using THC or something else in mice or cells. That’s not clinical evidence, which is the gold standard. Let me repeat an old adage–we have cured cancer over 100,000 times in mice. Because those models just tell us maybe it works. It never tells us that it does work.
- If you’re going to make a lame Big Pharma Shill Gambit to invent some claim that I, and my friends, are suppressing scientific knowledge about how valuable marijuana will be to “curing cancer.” Bring evidence, first by understanding what is cancer.
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