It's not for the state to decide what individuals put into their bodies in their own homes, writes Digital Clubbing columnist Alastair McAlpine. But no one should be under any illusion that the evidence for medical benefit from marijuana is both evanescent and insubstantial.
McAlpine writes:
The decision by the South African Constitutional Court (CC) to legalise the private cultivation, possession and consumption of marijuana is long overdue. What individuals choose to put into their bodies in their own homes is none of the state’s business. It is also a complete waste of time for an already stretched police force to be searching out pesky potheads to throw in prison.
But the downside to this decision is that many quacks have come to the fore with their kooky ideas that marijuana can cure everything from cancer to insomnia. The truth is, much like the smoke from a fat blunt, the evidence for medical benefit from marijuana is both evanescent and insubstantial.
There is a pervasive narrative that marijuana is a ‘wonder drug’ that has been wrongfully suppressed by an establishment that is both beholden to Big Pharma AND a bunch of killjoys. When I recently tweeted that ingesting marijuana was not a particularly good idea from a health perspective, with little to no medical benefit, a dense cloud of cannabis cranks descended swiftly on my account, accusing me of, like, being hopelessly out of date with the amazing properties of weed, dude.
So let’s take a closer look.
Marijuana is a plant which contains many biologically active substances. The most well-known and effective of these is tetrahydrocannabinol (THC), present in the leaves, seeds and stalks of the plant. As any hardened pothead will tell you, marijuana can be smoked, vaporised or ingested, and once the THC enters the blood stream, it binds to the cannabinoid receptors situated throughout the body.
Its effects begin fairly rapidly, precipitating the feeling of being ‘high’ – a slight feeling of drowsiness, an intense sense of self-awareness, and a generally relaxed outlook (or so I’m told…). It also, however, causes impaired cognition, memory retention, reflexes and concentration. At its worst, there can be intense paranoia, or a sensation of impending doom. Long-term, marijuana use has been associated with the development of psychosis and schizophrenia, and smoking it has similar carcinogenic effects to tobacco.
For the majority of its history, in most countries, marijuana has been illegal. Fairly recently, some US states, and countries like Canada, have legalised ‘medical marijuana’ as long as it offers ‘therapeutic benefit’. The definition, however, of what constitutes offering ‘therapeutic benefit’ is as variable as the size of a college student’s joint. What this means is that all sorts of fantastical and miraculous effects have been ascribed to the humble weed: some out of a cynical attempt to broaden the scope of conditions that permit access to the marijuana, and some out of a sincere belief that extraordinary properties are hidden beneath the sweet odour.
So let’s look at the evidence. There are a surprisingly large number of studies out there, but the Alberta College of Physicians has done an outstanding job of examining over 1,000 of them and providing a concise summary. You can read it here.
Perhaps the biggest claim of the pro-marijuana lobby is the effects of the herb on pain. So what does an appraisal of the literature show?
Although more people experienced chronic pain reduction than placebo (39% vs 30%), this means that 11 people would have to be treated for one to benefit. In addition, the improvement was clinically negligible (0.5 on a pain scale of 1-10).
The effects on acute pain and cancer-related pain were even less impressive. The only area where significant improvement was noted was neuropathic pain, where between six and 14 people required treatment for one to show benefit.
What about non-pain conditions? There is reasonable evidence that it is beneficial in those with severe nausea from chemotherapy, and a few small studies indicate that it may help some children with intractable epilepsy (such as Dravet syndrome), but only in combination with traditional anti-epileptic drugs. Evidence is extremely poor for benefit in psychiatric conditions like anxiety or depression.
But before you go lightning up, it needs to be noted that adverse events were frequently reported: 79-92% of patients reported at least one negative side effect. These resulted in 7-14% of patients discontinuing treatment (vs. only 1-5% of placebo takers). These side effects ranged from the fairly prosaic (dizziness) to the outright serious (hallucinations, hypotension, dysphoria).
Both the type of marijuana (synthetic vs. natural) and method of ingestion (eaten, smoked, vaped) made little difference on outcomes. It also is interesting that the larger and more robust the study, the less impressive the effect noted. It is also important that ‘blinding’ was unsuccessful in most of the studies, with 90-95% of patients and doctors knowing when they received cannabis vs placebo (amazing, I know).
By far the most nefarious claim for marijuana is that it has curative properties for those with cancer. Googling ‘cancer and marijuana’ leads one down a depressing rabbit hole of increasingly hyperbolic claims for its efficacy. ‘200 trials show cannabis kills cancer!’ screams the latest Facebook update from your hippie pal, Zach. ‘Read the research Big Pharma doesn’t want you see!’ claims the post from Aunt Bessie, whose friend Dora took it for her shingles, and just swears by the stuff.
But when we actually look at these papers (Digital Clubbing reads them so you don’t have to), it quickly becomes obvious that the vast majority are either in vitro or animal studies, with very, very little data on humans. Why is this a problem? Well, one study, for example, showed that in a test tube, cannabis could kill breast cancer cells, at a concentration of 10mmol/L.(1)
So what’s the catch? Skeptical Raptor noted here that to achieve that concentration in the blood, a user would have to smoke approximately 1,000 joints per day (your pal Zach at this point is no doubt thinking, ‘I don’t really see a problem there…’). This shows that just because a substance kills cancer cells in a lab, getting concentrations to effective levels in humans is often impossible.
Worryingly, there is also evidence that cannabis may stimulate certain cancers by causing a proliferation of cancer cells, while inhibiting their destruction.(2)
When we do look at the studies on humans, there very few, and some are obviously impractical (like the study that infused cannabis directly into the brain)(3), or use compounds that aren’t actually marijuana, like Amandamine. Even when we include these, we see very modest changes in cell growth or spread. In their entirety, the studies provide evidence that cannabinoids provide ‘reasonable, albeit by no means spectacular, anti-tumor effects in pre-clinical models’, as David Gorski at Science Based Medicine noted.
The American Cancer Society sums it up succinctly: “There is no available scientific evidence from controlled studies in humans that cannabinoids can cure or treat cancer.”
Aha! But aren’t all the cancer societies in the pocket of Big Pharma anyway? Don’t they stand to lose a fortune if cannabis oil is shown to be a successful treatment? Well, not really. By far the biggest producers of cannabis oil are likely to be Big Pharma. Already, Epidiolex, made by GW Pharmaceuticals, has been approved for use in childhood epilepsy. The same company released Sativex, for use in those suffering from multiple sclerosis (despite there being almost no evidence, as noted above). Trust me, no one wins more from the legalisation of marijuana than Big Pharma.
This hasn’t stopped the unscrupulous from making a killing (literally) from selling cannabis oil to the desperate. Naturopaths often fuel this misconception by over-hyping the benefits of marijuana and instilling false hope in their patients. When I was a palliative physician last year, a number of my oncology patients were sourcing cannabis oil illegally under the impression that it could cure or improve the disease in their terminally ill children. This oil was generally procured from a kindly old lady in a town outside Cape Town, and sold for approximately R3,000 for a 10ml syringe. The father of one of my patients had to mortgage his house to afford the product. In none of those taking it did it make any appreciable difference. The kindly old lady, however, now lives in a mansion and drives a R1m BMW…
With the Constitutional Court’s decision, we are likely to see marijuana appearing in the news more and more regularly. We are also likely to be bombarded by headlines about the amazing things it can do. But as it stands, the evidence simply isn’t there, and until we have better data, you should treat all claims to the contrary with extreme suspicion.
Marijuana is, like alcohol, predominantly a way for adults to relax and have fun. Like many recreational substances, heavy, long-term use is probably not a great idea, but a lot of people get a lot of enjoyment from the odd toke, and if you’re one of them, that’s cool. Just don’t kid yourself that it has any real medical benefit, outside of mildly improving a handful of specific conditions.
Now where did I put my bong?
References
1. Shrivastava A, Kuzontkoski PM, Groopman JE, Prasad A: Cannabidiol induces programmed cell death in breast cancer cells by coordinating the cross-talk between apoptosis and autophagy. Molecular cancer therapeutics. 2011;10(7):1161-72.
http://mct.aacrjournals.org/content/molcanther/10/7/1161.full.pdf
2. Hart S, Fischer OM, Ullrich A: Cannabinoids induce cancer cell proliferation via tumor necrosis factor alpha-converting enzyme (TACE/ADAM17)-mediated transactivation of the epidermal growth factor receptor. Cancer research. 2004;64(6):1943-50.
https://www.ncbi.nlm.nih.gov/pubmed/15026328
3. Torres S, Lorente M, Rodriguez-Fornes F, Hernandez-Tiedra S, Salazar M, Garcia-Taboada E, et al: A combined preclinical therapy of cannabinoids and temozolomide against glioma. Molecular cancer therapeutics. 2011;10(1):90-103.
https://www.ncbi.nlm.nih.gov/pubmed/21220494
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