Study Finds Inhaled Cannabis an Effective Treatment for Neuropathic Pain

The inhalation of vaporized herbal cannabis is an effective treatment for neuropathic pain, according to the results of a recently published study by German researchers. The observational study also found that inhaled cannabis helped neuropathic pain patients with sleep problems, a common symptom experienced by at least half of those diagnosed with the sometimes-debilitating condition.

Neuropathic pain is a condition caused by disease or injury to the nervous system that results in chronic pain, abnormal sensations known as dysesthesia or pain from normally pain-free stimuli. About 30% of neuropathic pain cases are associated with diabetes, according to information from the Cleveland Clinic, but other diseases including alcoholism, shingles and central nervous system disorders such as stroke, Parkinson’s disease or multiple sclerosis can also cause the condition. Additional causes include chemotherapy or radiation treatment, amputation-induced phantom pain, nerve damage from trauma or surgeries and compression or inflammation of spinal nerves. Neuropathic pain is traditionally treated with medication, although the authors of the new study noted that many patients are unable to find adequate relief with commonly prescribed treatments.

“The expression of neuropathic pain is highly individual and symptoms, as well as response of patients to various analgesics, antidepressants, anti-epileptics or opioid therapy, vary greatly,” the researchers wrote. “Unfortunately, treatment of neuropathic pain frequently remains unsuccessful even after multiple trials with various analgesics.”

To conduct the study, researchers identified a cohort of 99 participants diagnosed with chronic neuropathic pain lasting at least three months who had a high severity of symptoms and had exhausted other treatment options. The study was conducted in Germany, where the medical use of cannabis was legalized in 2017 for patients suffering from a chronic disease for which conventional treatment methods have already been exhausted. Participants were prescribed herbal cannabis, which is available at German pharmacies by prescription as dried flowers. All patients used cannabis with a THC concentration of 12-22%, while nearly two-thirds (64%) of participants used cannabis with a THC potency of 16-22%. Patients were instructed to use a vaporizer to inhale cannabinoids from heated cannabis flower. Participants chose their own plan of administration over a period of six months, deciding whether to use cannabis on a set schedule, as time permitted or when they experienced a pain attack.

Participants of the study completed a video consultation with a physician every four to six weeks throughout the six-month study period. Pain was assessed using a scale from 0 to 10. According to the German Pain Society, pain scores above 6 are defined as severe pain, which significantly affects a patient’s quality of life. Patients’ sleep disturbance was also assessed using a scale from 0 to 10. The National Institutes of Health reports that 50% to 80% of neuropathic pain patients experience sleep problems, with the severity of sleep problems often related to the intensity of pain.

“Within six weeks of therapy, median pain scores decreased significantly from 7.5 to 4.0. The proportion of patients with severe pain (score >6) decreased from 96 percent to 16 percent,” the researchers wrote. “Sleep disturbance was significantly improved with the median of the scores decreased from 8.0 to 2.0. These improvements were sustained over a period of up to six months. There were no severe adverse events reported.”

Study Participants Reported Improvements in Pain and Sleep

At the onset of the study, the majority of patients had severe neuropathic pain, with 96% of participants having a pain score above 6 and a median pain score of 7.5 for the group. At the first follow-up consultation, which was conducted within six weeks of beginning treatment, 90% of participants reported an improvement in their general condition and pain was significantly reduced to a median pain score of 3.75. At five subsequent follow-up consultations, pain scores continued to decline before stabilizing at about 3.

Before beginning medical cannabis, a majority of the patients suffered from severe sleep disturbance with a median score of 8 out of the maximum of 10. A significant improvement in sleep was reported in the first follow-up consultation. The median sleep disturbance score dropped to 2, an improvement that was sustained until the end of the six-month observation period. The researchers noted that the improvement in sleep was likely due to the improvement in pain symptoms but added that “it is also possible that a direct effect of the medical cannabis plays a role.” A majority of patients achieved an adequate quality of sleep, which is “a crucial parameter of life quality.”

Over the entire observation period, 97 (99%) patients reported an improvement in their general condition at one or more follow-up interviews. The study participants reported mild side effects including dryness in mucous tissue (5.4%), fatigue (4.8%) and increased appetite (2.7%). In their conclusion, the researchers wrote that the results “demonstrated that chronic neuropathic pain can be effectively, sustainably, and safely treated with medical cannabis.”

The researchers acknowledged some limitations of the study, including a “possible bias in selecting patients who are more open-minded for inhaling medical cannabis.” The authors also reported missing data points and incomplete data sets, which they said were “an intrinsic weakness of a retrospective and observatory study.”

A report on the research, “Medical Cannabis Alleviates Chronic Neuropathic Pain Effectively and Sustainably without Severe Adverse Effect: A Retrospective Study on 99 Cases,” was published last month by the peer-reviewed journal Medical Cannabis and Cannabinoids.