Brain imaging shows where THC takes action to relieve pain perception, even for those with chronic pain. Proof that THC kills pain.
Cannabis is currently one of the most interesting substances to be studied in Western medicine. It has so many medicinal components, including cannabinoids, flavonoids, and terpenes. One of the main medical applications for one of its major cannabinoids, THC, is in the treatment of chronic pain. It is believed that THC kills pain.- Advertisement –
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Recent neuroimaging determined that THC was able to reduce pain in healthy participants, and this was associated with the brain region called the anterior cingulate cortex (ACC).
This section of the brain is densely populated with the CB1 receptors, which in turn are activated by THC. The study used a single dose of THC vs placebo for chronic pain as evaluated by a subjective pain rating scale and resting brain state of the ACC. A fMRI (functional MRI) machine was used to measure changes in blood flow throughout the brain.
There were 17 patients participating in the study, with an average age of the 33. The patients had chronic lower limp radicular neuropathic pain that centers around spine and legs. The subjects had to have experienced the condition for at least six months in order to participate in the study.
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They were all males, since it was determined that hormonal fluctuations due to menstruation can alter pain sensitivity. THC was given sublingually, where plasma concentration was reached maximum after 2-3hrs.
Prior to starting THC treatment, the subjects rated their pain level from zero to a 100. Scientist then scanned their brains using functional magnetic resonance. THC was administered, and after 1 hour, participants again reviewed their pain levels; 2 hours later they scanned their brains again. The meetings were separated by at least 1 week to enable for the possible THC washout, where the treatments were reversed. The patients receiving the THC on the first meeting, were given the placebo one week later and vice versa.
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It was determined that participants receiving the THC experienced less pain (subjectively) 35 out of 100, whereas the group with the placebo treatment rated pain 43 out of a 100. At the base level, without any treatment participants reported pain 53 out of a 100.
Pain is a complex, subjective experience consisting of the sensory and emotional domains. There are 2 major pathways which are interconnected and regulate the pain in the brain: ACC and somatosensory cortex. These pathways are anatomically connected and converge at the ACC. Disrupted functional connectivity between these 2 pathways resulted in the pain relief. Different treatments of the chronic pain seem to modulate ACC in some way and will ultimately alter pain perception.
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Interestingly, the pretreatment functional connectivity between ACC and sensory motor complex resulted in the improvement of the pain scores induced by the THC. Basically, this means that the higher positive functional connectivity at the baseline, more benefit was gained during the THC administration.
The result of the study was substantial pain relief compared to placebo, which is in agreement with the previous studies reporting the analgesic properties of the THC for chronic pain, particularly in neuropathic pain. The pain relief was associated with reduction in the functional connectivity of the ACC and sensory motor cortex.
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Some limitations of the study include the absence of women due to the menstruation-induced fluctuations in pain sensitivity. Also, larger scale, more statistically relevant studies are required to reproduce those results. Also, additional studies are needed to prove if the results of this study explain the cannabis mechanism of action on any chronic pain or is it unique to the neuropathic pain states.
It should be also emphasized that the cannabis plant contains a multitude of the cannabinoids apart from the THC, and these compounds may play important roles in the clinical properties of the plant through the entourage effect.