THC significantly reduced patients’ pain compared to placebo.
Findings of a new study suggest that medical marijuana eases chronic nerve pain by reducing specific connections in the brain. Researchers from the Sagol Brain Institute at Tel Aviv Medical Center in Israel investigated the effects of tetrahydrocannabinol (THC), the intoxicating compound in cannabis, on 15 men diagnosed with radicular pain.
Radicular pain is nerve pain that centers around the spine and radiates into the lower extremity. It is caused by compression or inflammation of a spinal nerve root. Sciatica, which affects as many as 40 percent of people in their lifetime, is a common form of radicular pain.
Episodes of radicular pain can range in severity, from an irritating ache to discomfort so intense that it is hard to stand or walk. The sensations associated with radicular pain vary from a dull soreness, numbness, or tingling, to a throbbing heat or stabbing pain.
To study THC’s effects on radicular pain, the researchers had each of the 15 participants rate their pain levels on a scale of zero to 100 and took a magnetic resonance imaging (MRI) scan of their brains. They then gave nine of the men 15mL of THC under their tongue, while the remaining men were given placebo oil.
An hour later, the researchers asked the participants to report their pain levels. Two hours later, they scanned their brains again.
The entire process was repeated a week later, with those originally given the THC oil given the placebo, and those who had the placebo given the THC oil.
The researchers found that patients given THC experienced less pain than those given a placebo. Before taking the medication, on average participants rated their pain levels at 53. After given placebo, they rated their pain at an average of 43. Following THC treatments, the participants rated their pain levels at an average of 35.
Additionally, the MRI scans indicated that those given THC had a reduction in the connections in both the anterior cingulate cortex and the sensorimotor cortex – two parts of the brain that process pain sensation.
“Pain is a complex experience that involves both the senses and emotions,” said study author Haggai Sharon, MD, in a statement. “Our study results link pain relief from THC with a reduction in the connections between areas of the brain otherwise heavily connected, suggesting that THC may alleviate pain by disrupting signals between these pain processing pathways.”
The researchers also found an association between the amount of brain connections and the level of pain relief THC provided.
“Interestingly, our results also show that the more connected the areas of the brain that process emotion and sensory prior to treatment, the greater the pain relief experienced when taking THC,” said Sharon. “Larger studies are needed to confirm our findings.”
The researchers used only men in the study to eliminate any pain sensitivity changes caused by hormone fluctuations during menstruation.
The full text of the new study, “Cannabis analgesia in chronic neuropathic pain is associated with altered brain connectivity,” is available through Neurology, the medical journal of the American Academy of Neurology.