Few would disagree that there is currently a seeming tidal wave of public opinion supporting the legalisation of cannabis for medical purposes. However, in a surprising twist, a pilot study carried out in Colorado, the first US state to legalise cannabis for medical use, has concluded that over time cannabis may actually reduce pain tolerance in users.
Medicinal cannabis is widely advocated for a variety of chronic conditions. There is evidence that it can lessen spasticity in Multiple Sclerosis, reduce the number and severity of seizures for some people with epilepsy, help people with drug and alcohol addictions fight their dependency and relieve PTSD and depression.
Of course, medicinal cannabis is perhaps most widely used by people suffering chronic pain.
However, until now there has been no research on the effect or otherwise of long term cannabis use on pain tolerance levels during a subsequent episode of acute pain, perhaps following an accident or surgery.
In the pilot study, which has been published in the journal, Patient Safety in Surgery, during periods of acute pain, on average cannabis users rated their pain marginally higher than non-users (4.9/10 as compared to 4.2/10) and required higher doses of opioid-based painkillers (7.6 mg as compared to 5.6 mg daily). The authors have therefore hypothesised that cannabis may weaken the body’s resilience to pain over time.
This was only a pilot study. Of the 261 patients studied, of whom all had been hospitalised following motor vehicle accidents, only 16 (approximately 6%) admitted to long term cannabis use. Certainly, it is questionable how much useful information can be gleaned from such a modest sample size and significant caution is therefore required at this stage. Given the results, however, it’s not surprising that a larger scale study is planned. The authors concluded:
“These preliminary data suggest that marijuana use, especially chronic use, may affect pain response to injury by requiring greater frequency and dosing of opioid analgesia. These results were less pronounced in patients who used other drugs. With the increasing prevalence of marijuana use and abuse, and the frequency in which patients with traumatic injury also report substance abuse, our findings have important and potentially well reaching clinical implications. We are planning a larger prospective study to further investigate the relationship between substance use, opioid analgesics, and acute pain management in traumatic injury.”