Panel: ‘Weak’ evidence supports using medical cannabis to treat chronic pain


An international panel of experts reported that non-inhaled medical cannabis or cannabinoids were associated with modest benefits in patients with chronic pain.

Heretofore, most research has focused on the consequences of recreational cannabis use, Jason Busse, DC, PhD, a panel member and associate director of McMaster University’s Michael G. DeGroote Centre for Medicinal Cannabis Research in Ontario, Canada, and associate professor of anesthesia, said in a press release.

“The increasing legalization of medical cannabis globally, escalating use by patients, lack of training in the use of medical cannabis or cannabinoids during formal medical education, and inconsistent guidance from professional associations and federal agencies have led to confusion regarding the role of medical cannabis in the management of chronic pain,” Busse and colleagues wrote in The BMJ.

The researchers used the GRADE approach to analyze a linked series of four systematic reviews that examined the benefits, harms, patient values and preferences regarding medical cannabis or cannabinoids. The review included 32 randomized clinical trials.

After evaluating the data, the panel members wrote that they were “confident” that non-inhaled cannabis or cannabinoids use resulted in:

  • “a small increase in the proportion of people living with chronic pain experiencing an important improvement in pain and sleep quality”;
  • “a very small increase in the proportion of people living with chronic pain experiencing an important improvement in physical function”;
  • a lack of improvement in “emotional functioning, role functioning or social functioning”; and
  • “a small to very small increase in the proportion of people living with chronic pain experiencing cognitive impairment, vomiting, drowsiness, impaired attention and nausea, and a moderate increase in the proportion of individuals experiencing dizziness that increased with longer follow-up.”

Based on the evidence, the panel made a weak recommendation to consider a trial of non-inhaled medical cannabis or cannabinoids for people with chronic pain when standard care and management were not sufficient. The recommendation applies to patients with cancer and non-cancer pain, neuropathic pain, nociceptive pain and nociplastic pain.

“Therapeutic trials should start with low-dose, non-inhaled cannabidiol products, gradually increasing the dose and THC level depending on clinical response and tolerability (such as starting at a dose of 5 mg CBD twice daily and increasing by 10 mg every 2 to 3 days to a maximum daily dose of 40 mg),” the panel wrote. “If response is unsatisfactory, clinicians may consider adding 1 mg to 2.5 mg THC per day and titrating 1 mg to 2.5 mg every 2 to 7 days to a maximum of 40 mg/day.”

Due to a lack of sufficient evidence, Busse and colleagues noted that the recommendations “may or may not apply” to pediatric patients, veterans, patients with simultaneous mental illness, those receiving disability benefits and those who are involved in lawsuits. The recommendations do not apply to those in palliative care.

The panel also emphasized that their recommendations do not apply to recreational use of cannabis or cannabinoids, nor to inhaled versions of these substances.

Regarding safety, Busse and colleagues reported that “serious adverse events are unlikely with medical cannabis or cannabinoids, and patients cannot fatally overdose.”

“Dizziness is the most common non-serious adverse event with medical cannabis treatment,” they wrote. “Evidence regarding adverse effects of medical cannabis or cannabinoids use during pregnancy or breastfeeding is inconclusive: pregnant women or women contemplating pregnancy should be encouraged to discontinue use of medical cannabis in favor of alternative therapy. Cannabis use during breastfeeding should be discouraged.”

In a related editorial, Edeltraut Kröger and Clermont EDionneprofessors in the departments of pharmacy and medicine, respectively, at the Université Laval in Quebec, wrote that Busse and colleagues’ recommendations may enhance the shared decision-making process between physicians and patients.

“Clinicians should emphasize the harms associated with vaping or smoking cannabis and, as recommended by other guidelines, suggest products with known compositions such as nabilone or nabiximols, discourage self-medication and pay particular attention to vulnerable populations,” Kröger and Dionne wrote.