Given the recent thawing in political attitudes in New South Wales and Victoria towards so-called medical marijuana, one could be forgiven for assuming that the medical care of certain individuals is being disadvantaged by the lack of access to THC (tetrahydrocannabinol) products. One of the most frequently cited reasons for legalising marijuana for medical use is its efficacy for chronic pain.
By way of background, there is no dispute scientifically that molecules derived from marijuana (cannabinoids) are involved in pain signalling. The class of biological molecules that activate this system are called endocannabinoids and their biological activity is very complex. The sheer complexity of these actions is essentially the problem with finding suitably safe and effective medications for pain. There is an enormous amount of crossover from pain regulation into other brain functions such as motivation, memory, appetite and thermoregulation (body temperature control). The basic science is complex, and clinical trials to date have been disappointing. This usually suggests we have more to learn before a treatment is ready for adoption. When we have the clinical pharmacology of a drug nailed down, the results in trials are usually clear cut successes.
If you want a slightly technical but very accurate and balanced view of the current state of the evidence regarding the risks and benefits of cannabinoids in pain, you can read these lecture notes. If you don’t have the time or inclination, the summary of the serious literature is as follows:
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The evidence supporting efficacy in neuropathic pain or any type of chronic pain is mixed, and the basic question of whether it really works is a long way from settled.
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The most generous estimate of the effect size for THC-derived products in clinical trials to date is small. Simply put, THC-derived products are about as useful as paracetamol for pain.
- There are significant concerns that lifetime consequences can occur from periods of exposure to THC-derived products, particularly in adolescence and young adulthood.
- Currently available prescription products such as Sativex do not have evidence supporting their efficacy in pain conditions that would qualify them for serious consideration. They do have evidence of side effects and potential harm, like all prescription drugs.
The situation regarding hemp oil and other “cottage industry” products is even less encouraging. There is no compelling evidence that stronger preparations are better for pain relief than the relatively less potent ones available on prescription. The quality and safety of such products is unregulated and does not deserve any sober consideration as a useful treatment for pain. They may be highly regarded by connoisseurs but they don’t even approach the benchmarks for ethical prescribing.
Is more research needed? Yes, I think much more research is needed into endocannabinoids to identify more promising targets for new drugs. Do we need any more trials looking at hemp oil or other currently available forms of cannabinoids? Not really. We would probably get better value for increasingly scarce research dollars by looking at other more promising treatments.