Ongoing research and development into the study of cannabis and its effects on the human body consistently reveal intriguing advances and a better understanding of how cannabinoid consumption can benefit an array of conditions. One such effect that has been associated with cannabis use through anecdotal evidence for years, and is now becoming better understood through scientific study, is the analgesic or pain-relieving properties it can provide.
One study investigated the relationship between cannabinoid blood concentrations and the body’s analgesic response when vaporizing cannabis.  Interest in a study of this nature was sparked by a search for alternative methods for neuropathic pain treatment and to see if cannabis consumption displayed direct effects towards the analgesic response of test subjects. Cannabis represented a potential alternative treatment to neuropathic pain as modern pharmaceutical therapy for this condition exhibits little benefit or is altogether ineffective in 40%-60% of patients experiencing the problem. [1,2]
The study involved administering different doses of vaporized cannabis on 42 subjects who had neuropathic pain related to disease or spinal cord injury. Subjects were given either a placebo, a dose of 6.7% delta-9-tetrahydrocannabinol (THC) cannabis or a dose of 2.9% THC cannabis. Everyone was given two doses in a 4-hour window and pain assessment tests and blood samples were collected over the course of the study. The blood samples were then analyzed to compare plasma concentrations of certain cannabinoids in relation to direct changes in the test subjects’ pain levels as measured by a percentage in change on the Neuropathic Pain Scale. 
Results from the study were intriguing as they indicated a direct correlation between vaporized cannabis consumption and a decrease in neuropathic pain. Subjects saw improvements in their pain scores on the Neuropathic Pain Scale when administered both doses of vaporized THC.  The findings also show a direct correlation between the concentration of THC administered and its effect to improve analgesic response as higher concentrations led to increases in pain relief.
The sample size of this study and number of blood samplings were small, and the results did not reach statistical significance after false discovery rate adjustments to control for false positives. But the study does provide preliminary supporting evidence to indicate that cannabis can indeed aid in reducing neuropathic pain and that there is a direct correlation between blood plasma cannabinoid concentrations and an analgesic response in humans.
- Wisley, Barth L, et al. “A Preliminary Evaluation of the Relationship of Cannabinoid Blood Concentrations with the Analgesic Response to Vaporized Cannabis.” Journal of Pain Research, 2016, vol.9, pp.587-598. Journal Impact Factor = 2.581, Times Cited = 15
- Dworkin, RH, et al. “Symptom Profiles Differ in Patients with Neuropathic Versus Non-Neuropathic Conditions.” J Pain, 2007, vol.8, no.2, pp.118-126. Journal Impact Factor = 4.519, Times Cited = 79
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