Although many people have never heard of it, neuropathy is a tricky to treat, painful, and surprisingly common condition. About 20 million people in the U.S. have neuropathy, including one in four people over age 65, and nearly half of people with diabetes, with 15% of those experiencing pain. But it’s not just diabetes that can cause it. HIV, alcoholism, autoimmune disease, chemotherapy, and other triggers—often unknown—can cause the peripheral nerve damage that results in ongoing numbness, weakness, tingling, and pain, usually in the hands and feet.
That’s where medical marijuana comes in. Peripheral neuropathy can cause stabbing or burning pain that can have a serious impact on the quality of life. People with neuropathy can experience depression, have trouble with their ability to work, and other problems.
Part of the reason is that traditional treatments aren’t always successful at relieving the pain. In addition to uneven results, treatments can also have side effects. Neuropathy can be treated with antidepressants, like tricyclic antidepressants and selective serotonin and norepinephrine reuptake inhibitors, some of which have side effects like decreased libido. Neuropathy is also treated with anti-seizure medications, like gabapentin, which can cause dizziness and memory loss. There are also pain relievers, like NSAIDS, or even opioids, although they tend to be a treatment of last resort due to the risk of addiction.
There are less invasive options like capsaicin cream, a hot pepper-derived chemical, which may help some people, some of the time. And there are more invasive treatments, including spinal cord stimulation.
Given that neuropathy is difficult to treat, and treatments carry a risk of side effects, it’s logical to take a look at medical marijuana, a natural remedy used to treat pain. The human body has a naturally occurring endocannabinoid system that modulates pain, with cannabinoid receptors in both the central and peripheral nervous systems. After a nerve injury, neuropathy is thought to occur because of a maladaptive response that causes the nerves that typically detect sensations to become more sensitized and reactive to stimuli. Marijuana contains 500 compounds, including 80 cannabinoids, that may interact with naturally-occurring pain-modulating receptors, although it’s not clear if they help this maladaptive response. The two most abundant and most studied chemicals in marijuana are tetrahydrocannabinol (THC) and cannabidiol (CBD).
So does cannabis work? Like most research on medical marijuana, studies are relatively small and for relatively short periods of time. But the good news is that there is more research on the use of cannabis for peripheral neuropathy than some other conditions
Overall, smoking or inhaling cannabis may relieve pain and possibly help sleep and improve function better than a placebo for at least some people with neuropathy. However, side effects are also common, particularly at high doses. They can include difficulty concentrating, fatigue, and a rapid heartbeat, as well anxiety, paranoia, or even psychosis.
For example, a 2015 meta-analysis published in the Journal of Pain, looked at five randomized, placebo-controlled trials of inhaled cannabis for chronic neuropathic pain due to HIV, diabetes, or trauma, including a total of 178 patients who were treated for days or weeks. The authors concluded that one in every five to six patients would get short-term relief from pain. Side effects were rarely bad enough for people to drop out of the studies, although one person on a placebo experienced psychosis and two in the cannabis group dropped out, one for high blood pressure and the other for increased pain. Other mild side effects that were reported were anxiety, disorientation, headache, and dry eyes, among others.
In one randomized study specifically in patients with diabetes with painful neuropathy, researchers looked at the efficacy of inhaled, vaporized cannabis in 16 people in a randomized, placebo-controlled trial. People tried it as low (1%), medium (4%), or high (7%) doses of THC and were tested for the next three hours. All doses reduced pain compared with placebo, but the high dose also impaired performance on a two out of three neuropsychological tests.
Keep in mind that the marijuana used in clinical trials is usually provided by the National Institute of Drug Abuse (NIDA), and may vary in potency and composition from that commercially available cannabis, according to a 2018 report in the Cleveland Clinic Journal of Medicine. Higher THC levels found in commercially available cannabis may be more likely to cause side effects, they said.
“NIDA varieties contained much lower THC levels and as much as 23 times the cannabinol content as cannabis in state-legalized markets,” Vania Modesto-Lowe, MD, of the University of Connecticut School of Medicine, Farmington and colleagues write.
They conclude that the treatment may not be appropriate for those who already have depression, anxiety, psychotic disorders or respiratory conditions.
In a comprehensive Cochrane review that was published in 2018, a team reviewed 16 randomized, placebo-controlled trials including 1750 patients treated from 2 to 26 weeks. In most of the studies, patients used an oromucosal spray containing THC and CBD. In other trials, patients were treated with nabilone, a synthetic cannabinoid that mimics THC; inhaled herbal cannabis; dronabinol, which is a plant‐derived THC; or dihydrocodeine, an analgesic.
About 21% of patients achieved 50% or greater reduction in pain with cannabis-based medicines compared to 17% taking a placebo. About 39% achieved 30% or greater pain relief compared with 33% taking a placebo. However, more people—10% in active treatment vs 5% on placebo—dropped out of the studies due to side effects like sleepiness, dizziness and other problems, like confusion. Psychiatric disorders occurred in 17% of people in the active treatment group compared with 5% taking placebo.
The authors concluded that “the potential benefits of cannabis‐based medicine (herbal cannabis, plant‐derived or synthetic THC, THC/CBD oromucosal spray) in chronic neuropathic pain might be outweighed by their potential harms.”
If you want to try medical marijuana for neuropathy, you should check with your physician to see if it’s appropriate for you. You can also check your state’s medical marijuana legislature to see if you qualify. Medical marijuana is approved through publicly available comprehensive program in 34 states and the District of Columbia, according to the National Conference of State Legislatures. Each state varies in terms of medical conditions that qualify for the medical program, and the cause of neuropathic pain may matter. For example, in Connecticut, you would qualify for a medical marijuana certificate if you have facial neuropathic pain or neuropathic pain due fibromyalgia or a spinal injury. A diagnosis of HIV or cancer also qualifies, and both can lead to neuropathy.
An additional 12 states either have approved or offer limited access to marijuana products, typically low THC, high cannabidiol products, for specific conditions (usually intractable epilepsy.) Alabama is the only state that lists chronic pain as a condition that meets its criteria for these products.
Theresa Tamkins is a health writer and editor who has worked for BuzzFeed News, Health.com, Reuters Health and other publications.