Over the last 12 months New Zealanders have entered into the debate about cannabis and cannabinoids for medical use. In the coming year we’ll hear even more about cannabis as we consider legalising cannabis for recreational use. There is so much rhetoric around the issue, and so much misinformation I thought it high time (see what I did there?!) to write about where I see the research is at for cannabis and cannabinoids for persistent pain.
For the purposes of this blog, I’m going to use the following definitions: Cannabis = the plant; cannabis-based medication = registered extracts (either synthetic or from the plant) in standardised quantities with quality assurance; cannabinoids = substances found in cannabis that may or may not be synthesised into cannabis-based medication.
I’m going to divide this post into two: one part is about cannabis and cannabis-based medication for persistent pain; and the other is about cannabis for recreational purposes.
Cannabis is really popular in New Zealand. Growing up in Gisborne, one of the prime growing regions because of its long, warm summers, cannabis was common. I’ll put my hand on my heart and say I didn’t try it because I was a bit of a nerd and didn’t even try alcohol until I’d left home at 17!
Ministry of Health estimates that eleven percent of adults aged 15 years and over reported using cannabis in the last 12 months (defined here as cannabis users). Cannabis was used by 15% of men and 8.0% of women. Māori adults and adults living in the most deprived areas were more likely to report using cannabis in the last 12 months. Thirty-four percent of cannabis users reported using cannabis at least weekly in the last 12 months. Male cannabis users were more likely to report using cannabis at least weekly in the last 12 months. The NZ Drug Foundation reports that ” In the 2015/16 year, 80% of the adult population reported drinking alcohol once or more – 31% reported drinking at least twice a week.”
The harms from cannabis are real: for vulnerable people, particularly teens with developing brains, the foetus, and those with other mental health problems are more likely to experience adverse effects including psychosis. This risk increases with the greater THC content. The mix of cannabis plus alcohol is nasty… But I’m more concerned about the harms from prohibition.
Prohibition for alcohol didn’t work. Illicit stills, home brewing, fruit-based alcohol concoctions were all readily available during the prohibition era in New Zealand (see this about Hokonui Moonshine). Why would we think prohibition would be effective for cannabis? In fact, the harms from prohibition are this: limited calm and reasoned discussion about adverse effects of cannabis; disproportionate targeting of Maori for possessing cannabis; the use is underground so there is no quality control of the product; gangs use their control of cannabis to threaten purchasers; the real health and addiction problems of cannabis can’t be addressed because it’s illegal while the funding used by police and the justice system could be redirected towards helping the vulnerable. And there are undoubtedly other harms as well.
For my money, I’m quite comfortable with legalising and then controlling the quality of cannabis for sale in New Zealand. With good safeguards around the age required for purchase and redeploying the money currently spent policing and imprisoning people for cannabis crimes to health services, I think we’d do ourselves a great favour. Not quite so happy about commercialising the product because with competition there’s always an increase in efforts to sell more, but with good controls I think it will be far better than our current situation.
Now. Onto cannabis for pain, and cannabis-based medications for persistent pain.
I’ve been reading a LOT of research exploring cannabis and cannabinoids for persistent pain. To limit the extent just a little, I’ve looked only at cannabis and cannabis-based medications for neuropathic pain. This is for a couple of reasons: cancer pain is different from non-cancer pain, and there are often different considerations for cancer pain. Most of the animal research (rats, mice) uses a neuropathic pain model. Neuropathic pain is one of the more difficult persistent pain problems to treat pharmacologically. There’s more, and better quality, research into cannabis, cannabis-based medications and cannabinoids in neuropathic pain than any other pain mechanism. BUT it’s important NOT to extrapolate from findings in rats and mice, and for neuropathic pain, to all forms of pain in humans. That being said, here’s where things are at.
In neuropathic pain, cannabis-based medications are either a combination of THC + CBD or they’re straight THC. CBD has not been studied on its own for pain. This is important because, according to a study I’ve just been involved in, and from listening to people about their experiences of using cannabis for pain, most people think a CBD-based or CBD-heavy drug is “good for pain”. Recently I reviewed a study of cannabis for fibromyalgia (here) where it was only the plant with THC or THC + CBD that gave people pain reduction. There is some thought that CBD augments the effects of THC, but only in certain proportions – there’s a reasonably small window in which THC + CBD is helpful in pain.
The controlled studies, using reasonable methods (and believe me, there are a LOT of studies using poor methods, and even poorer reporting) show that THC or THC + CBD are the only combinations to provide pain reduction.
The question we should be asking (and always ask before adopting a new treatment) is whether this is more effective than what else is on offer, and whether the adverse effects are fewer.
At this stage I have to say the evidence is pretty skinny. Lots of studies, yes, but not well-conducted or reported, and the change in pain intensity is small. So small that the change in pain scores was a reduction of 4mm on a 1 – 100mm visual analogue scale. And the number needed to treat for one person (to achieve a 30% reduction in pain) were 27 (38.5% response to treatment, 33% response to placebo) (Campbell, Stockings & Nielsen, 2019).
Now this finding conflicts with the many people who report using cannabis (not cannabis-based medications). Again, drawing from the study I have been involved in, many of the participants indicated that they found cannabis helpful – although a good proportion also identified that cannabis didn’t actually take the pain away. And this is interesting. Why is it that people say they use cannabis for pain (and pain is the most common reason given for using “medicinal” cannabis in the US (Kosiba, Maisto & Ditre, 2019)?
Drawing from both the study I’ve been involved, and some hunches, here’s what I think might be happening (more research required):
- Cannabis promotes a sense of euphoria. Now that doesn’t mean feeling super-high, but it does mean feeling better than before you had it. And if you’re experiencing pain that doesn’t go away, feeling good is such a contrast to what you’re feeling most of the time, I wonder if this explains some of the effect. Particularly as it’s the THC or THC + CBD combo that seems to have greatest effect in research.
- Cannabis often promotes better sleep, and this is one consistent report from the study I’ve been involved in. Disturbed sleep is, as we know, associated with greater pain the following day, and most people with persistent pain report rotten sleep (Simpson, Scott-Sutherland, Gautam, Sethna & Haack, 2018). Maybe one effect of cannabis use is to help people sleep better – but what are the effects of cannabis on sleep architecture in the long run?
- Using cannabis involves a ritual. A ritual either of baking, or of preparing to smoke weed. Rituals invoke a meaning response (Blease, Annoni & Hutchinson, 2018; Lindenfors, 2019). They prepare us for what is to follow. In time, we anticipate what happens next. In the case of cannabis, inhaled cannabis takes effect within seconds of inhaling, so it becomes a very potent learned expectation. In baked goods, the effect is far slower – but there’s little doubt that inhaling the scent of freshly baked goodies elicits all sorts of yummy expectations, whether the product is cannabis-laced or not! The meaning response (“placebo effect”) is an incredibly powerful product of our own nervous system – and I have no problems attributing at least part of the reported analgesic effect of cannabis to the meaning and expectations people hold towards its use. Add to the expectation some pharmacological feel-good substances, and it’s potent!
- Cannabis can be used prn whenever the person feels the need. While some people limit their use of cannabis to an evening toke, from our study some people indicated they used cannabis repeatedly through the day and evening. Because it’s not possible to kill yourself with a dose of cannabis, and because the euphoric effects quickly drop (if they’ve even been a significant part of the experience) cannabis use can be a pick-me-up any time. There are good, and not so good effects from this: prn medication use isn’t thought to be helpful because it can promote increased use over time. That doesn’t appear to be the case for cannabis. Again, prn use of any medication is thought to perhaps address distress rather than pain intensity, so it may mean people are less inclined to use active coping than reach for cannabis. I don’t know, because the research hasn’t been carried out. What does seem clear is that because of its rapid onset and relatively mild side effects as compared with opioids or the usual drugs for neuropathic pain, people are more positive about using cannabis as needed rather than these alternative drugs.
- Cannabis has fewer strongly sedating effects than many other medications for neuropathic pain. By this I do not mean it has no sedating effects (see above!). But participants in the study I’ve been involved in said they could function, they could participate in things that mattered to them while using cannabis, whereas with opioids or other drugs for neuropathic pain, they couldn’t because they felt groggy, spaced out, or just couldn’t think. I think this is really interesting. Maybe it’s worth being able to think straight is more important to our participants than having better pain reduction. The sedating effects of cannabis effects seem to wear off more quickly, particularly for people who use it a lot.
- Cannabis can reduce anxiety – but so also can it increase anxiety. People living with persistent pain, particularly weird neuropathic pain, live with the uncertainty of when it will flare up, when the “electric shocks” will start up again, wondering if it will settle down or hang around. This doesn’t engender a state of calm! Some forms of cannabis can reduce anxiety (particularly CBD-heavy forms), but THC-high (see what I did again!!) increase anxiety. It’s a mixed bag especially given that establishing the precise chemical consistency of plant material is pretty difficult – particularly by growers in the illegal market of NZ.
Summary – and a bit of science
Writing this blog I’m sure will bring out a heap of pro-cannabis people who will argue that I’m ignoring the “strong evidence” for cannabis for pain relief. Before anyone does – believe me, I’ve read a heap of papers, and to be perfectly honest, I’m alarmed at the state of the research. Not only are many studies failing to identify the pain mechanisms addressed (neuropathic pain is the most commonly studied, but it’s also common to find studies with mixed cohorts); studies are often short – for a chronic, ongoing problem like persistent pain, we need to have studies carried out over 12 months or more, 8 weeks or less is completely insufficient; the outcome measures used are primarily pain intensity using a unidimensional index like a numeric rating scale – come on guys, pain is NOT a unidimensional problem, and surely we’ve learned from opioid trials that pain intensity isn’t the best outcome measure for a long-term problem? What about participation in life? What about disability reduction? What about sleep? What about reduced use of healthcare? Many of the studies are in rats and mice and last time I checked, I’m not a rat or a mouse, and my physiology is a little different; the analysis of studies is often awful with no mention of dropout rates, no responder analysis, no description of adverse effects and tiny, tiny sample sizes. Worse, the small sample sizes exclude people with comorbid problems like depression, anxiety, insomnia, drug and alcohol use (and yet these are characteristics of many people seeking help for persistent pain). Additionally, most studies don’t indicate whether the people taking part in the study are naive to cannabis – people who use cannabis regularly are less likely to be bothered by adverse effects, so studies aren’t describing what may happen in people who are new to the effects of cannabis.
I could go on, but I think there are enough questions about the state of the research into cannabis for pain for us to be pretty cautious about asking medical practitioners (who may not have the time I’ve dedicated to reading the research) to sign their name to a prescription for a cannabis-based treatment, or cannabis itself. Doctors should think carefully before prescribing because, in health, we expect that medical practitioners know what substance they’re prescribing, the effects of that substance, what it should be used for, what harms might come from it, what interactions it might have with other medications, and that the product available has consistent quality-assured content.
As for understanding why people continue to use cannabis for pain – I’m keen to study this in more detail. Why is there such a disparity between what research shows and what people tell us? What might explain this? I’m absolutely not doubting the experience of people who say that cannabis helps – I’m just curious about how this is coming about, because it doesn’t look like it’s purely from the pharmacological effects of the plant.
Blease, C., Annoni, M., & Hutchinson, P. (2018). Editors’ Introduction to Special Section on Meaning Response and the Placebo Effect. Perspectives in biology and medicine, 61(3), 349-352.
Campbell, G, Stockings, E, Nielsen, S. (2019). Understanding the evidence for medical cannabis and cannabis-based medicines for the treatment of chronic non-cancer pain. European Archives of Psychiatry and Clinical Neuroscience, 269. pp 135 – 144. https://doi.org/10.1007/s00406-018-0960-9
Kosiba, J, Maisto, S, Ditre, J. (2019). Patient-reported use of medical cannabis for pain, anxiety, and depression symptoms: Systematic review and meta-analysis. Social Science & Medicine, 233, pp 181-192. https://doi.org.10.1016/j.socscimed.2019.06.005
Lindenfors, P. (2019). Divine Placebo: Health and the Evolution of Religion. Human Ecology, 47(2), 157-163.
Simpson, N. S., Scott-Sutherland, J., Gautam, S., Sethna, N., & Haack, M. (2018). Chronic exposure to insufficient sleep alters processes of pain habituation and sensitization. Pain, 159(1), 33-40.