By Pat Anson, PNN Editor

Long-term use of medical cannabis may be an effective treatment for chronic pain, according to a small study by researchers at Harvard Medical School and McLean Hospital in Boston.

Thirty-seven patients suffering from arthritis, joint pain, neuropathy and other chronic pain conditions were evaluated over a six-month period while ingesting cannabis products through smoking, vaporizing, edibles, oils and other methods. All of the patients were cannabis “naive” — meaning they had never used cannabis before or had abstained from use for at least a year prior to the study.

After six months of daily treatment with cannabis, patients reported significant improvements in their pain, sleep, mood, anxiety and quality of life. Their use of opioid pain medication declined by an average of 13% and 23% after 3 and 6 months of treatment, respectively, although not to a degree that was considered significant.

A control group of 9 pain patients that did not use cannabis did not have a similar pattern of improvement in pain or other symptoms. 

“This naturalistic study of medical cannabis (MC) patients with chronic pain provides preliminary evidence that ‘real world’ MC treatment may be a viable alternative or adjunctive treatment for a least some individuals with chronic pain,” wrote lead author Staci Gruber, PhD, Associate Professor of Psychiatry at Harvard Medical School. 

“As results also revealed that individual cannabinoids appear to exert unique effects on pain and comorbid symptoms, more research is needed to potentially optimize cannabinoid-based treatments for pain.”

Gruber and her colleagues say increased exposure to tetrahydrocannabinol (THC), the psychoactive ingredient in cannabis, appeared to be closely related to improvements in pain, while increased CBD exposure was related to improvements in mood, but not pain. Many patients reduced their use of THC as the study progressed.

“Interestingly, we have found that many patients aim to achieve symptom alleviation without experiencing the intoxicating effects of THC. Therefore, it is likely that patients are able to achieve adequate pain relief using lower doses of THC over time than initially utilized,” said Gruber, who heads the Marijuana Investigations for Neuroscientific Discovery (MIND) program at McLean Hospital.

Researchers say additional studies are needed to explore how THC and CBD modulate pain and other symptoms. Their findings are published in the journal Experimental and Clinical Psychopharmacology.  

While the findings are intriguing, the small number of patients involved in this and most other cannabis studies makes it hard to draw firm conclusions.  

Last month two professional pain societies – the International Association for the Study of Pain (IASP) and the Australian and New Zealand College of Anaesthetists -- released statements saying they could not endorse the use of cannabis to treat pain because there are no large, high-quality and unbiased clinical trials of cannabis as an analgesic.