Can cannabis help with neuropathy? The evidence seems to point to yes, and many US states and other countries now have approved the use of cannabis to treat it.
Research is ongoing, but there is a large and encouraging body of evidence suggesting that cannabis, with its impact on the endocannabinoid system — which is involved in neuropathic pain — is helpful.
By modulating the endocannabinoid system, cannabis may be effective at both reducing pains associated with neuropathy and promoting neurogenesis.
How Cannabis Works on Neuropathy
While the body produces its own natural cannabinoids that interact with the endocannabinoid system, the cannabinoids found in cannabis (such as THC and CBD) are also capable of activating endocannabinoid receptors.
There is strong evidence that the endocannabinoid system is involved in the expression of neuropathy. In animal models, ECS dysfunction has been shown to correlate with neuropathic pain. One study showed that when activity of CB1 — the primary ECS receptor in the central nervous — system was deleted, mice showed signs of increased pain. In another study, deletion of the CB2 receptor — primarily found in our immune system — also led to more pain in mice.
The more CB2 receptors we find in the central nervous system, the more we find a reduction in neuropathic pain. In animal studies of diabetic-induced neuropathic pain, along with chemotherapy-induced neuropathy, activating the CB1 and CB2 receptors also reduced pain. It is noteworthy that other studies using mice whose CB1 or CB2 receptors were blocked did not show changes in pain behavior in animals.
Rat models of neuropathic pain have also found reduced pain responses when CB1 and CB2 were activated. These researchers found that activation of these receptors before an injury could actually prevent the development of pain.
In addition, activation of CB1 and CB2 receptors has been found to promote neurogenesis — the process by which new neurons are formed in the brain. CB1 and CB2 activators increased cell proliferation and survival of brain cells and even restore changes that come with age in the brain. Since neurogenesis is decreased in patients with neuropathic pain, it is possible that increasing neurogenesis could be helpful for neuropathic pain.
Some studies also showed that activation of cannabinoid receptors allowed people to benefit from pain relief from a smaller dose of opiates.
Medical Studies on Cannabis and Neuropathy
There is a large body of preclinical research that suggests cannabis is effective at reducing neuropathic pain in rodents. But what about humans?
Thankfully, there are a few studies — and even some systematic reviews with meta-analysis — that look at whether cannabis might help with neuropathy. The results are generally positive.
A 2015 meta-review covering multiple studies found that several clinical studies demonstrated the pain-relieving effects of cannabis, particularly for pain associated with diabetes, multiple sclerosis, and chemotherapy — three common sources of neuropathic pain.
A 2017 meta-review on cannabis also found that there was conclusive evidence that cannabis is an effective treatment for chronic pain. While this review looked at studies on a variety of different types of chronic pain (including neuropathy), they found cannabis helped for all types of chronic pain studied — regardless of the condition. Acute pain however — like that experienced during surgery or immediately after an injury — was not helped by cannabis. Even more recently, a 2018 meta-review looking specifically at neuropathic pain found that cannabis performed similarly to other pharmaceutical options for pain relief.
One study found that patients who smoked cannabis with low doses of THC showed improvements in neuropathic pain relative to the placebo. A similar study using smoked cannabis with low doses of THC also found pain relief compared to the placebo for multiple sclerosis related pain. In addition, a randomized, double-blinded, placebo controlled study using inhaled cannabis showed a significant dose-dependent effect on pain in patients with diabetic peripheral neuropathy.
Taking cannabis orally can also be helpful. Studies on Sativex — a sublingual spray with equal parts THC and CBD — show it can provide relief from neuropathic pain. In one study on MS patients, Sativex showed pain relief when compared to a placebo at 10 weeks. However at 14 weeks there was no longer a difference between the placebo and Sativex — perhaps suggesting development of a tolerance to cannabis’ pain relieving effects.
Studies of Nabilone — a synthetic version of THC approved by the FDA have also shown positive results. One study found it was significantly more effective at treating diabetic neuropathy than the placebo.
While CBD isn’t as widely studied for neuropathic pain as THC, some studies have also shown that CBD leads to reductions of neuropathy for patients with diabetes.
Potential side effects of cannabis use
Despite the positive potential for cannabis treating neuropathy, cannabis comes with a wide array of potential side effects and these can be a deterrent for some patients.
In studies on patients with neuropathy, side effects were generally modest but included symptoms like light-headedness, mild difficulties in concentration and memory, tachycardia, dry mouth, nausea, and fatigue. These usually resolve within a few hours.
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