Cannabis is known to relieve pain, but pain can arise for a variety of reasons which makes choosing the right cannabis product tricky. Knowing which cannabinoids (e.g. THC, CBD) have been shown to treat different pain types is useful information to take with you on your next dispensary visit.

The different types of pain fall into three general categories:

Nociceptive pain

Neuropathic pain

Central pain (there’s no firm agreement on the name for this type of pain; fibromyalgia is a common example).

Since each type of pain has a different origin, each type has an optimal treatment strategy.

Pain results from the coordinated activation of brain cells. While these brain regions lead to the sensation of pain, they can also modulate the strength of the pain signals. In some instances, you can have physical injury (i.e., nociceptive pain) without the sensation of pain (imagine a car accident victim who can walk around pain-free in the initial moments after the accident).

But the opposite is also possible, where you can have pain in the absence of physical injury (i.e., central pain). This highlights the importance that factors like mood, context, and attention-to-injury play in the sensation of pain, which can also be used to inform optimal cannabis-based treatment strategies.

Cannabis and Nociceptive Pain

Nociceptive pain (i.e., inflammatory pain) results from tissue damage. It is subjectively described as sharp, aching, or throbbing pain that follows physical damage. When you get injured, the damaged tissues recruit numerous inflammatory and immune cells to repair the damage. These cells release proteins and chemicals that activate receptors on nerves that make their way into the spinal cord and up to the brain, causing the sensation of pain.

To retain pain-relieving efficacy while reducing tolerance risk, one should consider balanced THC and CBD products for long-term pain treatment.

Nociceptive pain can be weakened by reducing the pain signals at the site of injury by blocking the inflammatory process itself or the signals they elicit. Another strategy is to dampen their effects as they make their way up the spinal cord to the brain. Cannabis can target both of these processes to reduce pain.

The abundant cannabinoids, THC and CBD, can reduce pain at the site of injury. Both have potent anti-inflammatory effects. THC’s anti-inflammatory properties are primarily driven through activation of CB2 receptors on immune cells which dampens the body’s pain-inducing response to injury. CBD also reduces inflammation by blocking inflammatory mediators and shifting the activation macrophage repair cells from the pro-inflammatory type to the anti-inflammatory type. Indeed, the benefits of THC and CBD on relieving nociceptive pain have been well-documented in rodent models of inflammation and in human clinical trials.

THC can modulate pain at the level of spinal cord and brain by directly activating CB1 receptors, and indirectly by increasing opioid receptor activation (more on that in part two of this series). CBD similarly impacts pain processing by increasing levels of the endogenous cannabinoid, anandamide, which acts like THC to activate CB1 receptors.

CBD also has a host of targets beyond the endogenous cannabinoid system (ECS) that can relieve pain. Of particular relevance, CBD enhances the activity of receptors for the brain’s primary inhibitory neurotransmitter, GABA. Through this inhibitory effect, CBD can dampen pain signals as they make their way into the brain.

When you’re feeling good, you’re less likely to focus on the things that hurt. Not only does a positive mood shift your attention away from the things that bother you, but it can also directly reduce the strength of pain signals that enter the brain. It’s a mind-over-matter phenomenon and it can be powerful when it comes to pain, at least at the beginning.

Over time, it becomes more difficult to achieve the positive feelings associated with cannabis consumption and weaken its pain-relieving effects. This is the consequence of tolerance to THC’s activation of CB1 receptors, which can be mitigated by CBD. Consequently, to retain pain-relieving efficacy while reducing tolerance risk, one should consider balanced THC and CBD products for long-term pain treatment.

CBD can also improve mood by activating serotonin receptors, which has anxiety- and stress-reducing effects. Since depression and anxiety are common among those in chronic pain, the mood-improving effects of CBD makes it a valuable addition in pain therapy.

Cannabis and Neuropathic Pain

Neuropathic pain is different from nociceptive pain in that arises from damage to the body’s nervous system. And it’s quite common. Neuropathic pain affects 7-10% of the population and can result from forceful injury, pinching, or stabbing that damages nerves. Disease is also a common underlying cause of neuropathic pain. For example, in multiple sclerosis, the insulation of nerve cells breaks down which leads to neuropathic pain. Other diseases that cause neuropathic pain include Parkinson’s disease, HIV, diabetes, and shingles, to name a few. Chemotherapy is an additional common cause of neuropathic pain due to its destructive effects on many types of cells in the body.

Like with nociceptive pain, over-activation of CB1 receptors with THC can eventually lead to weaker effects. Therefore, balanced THC and CBD cannabis would be more efficacious in the long-term.

Neuropathic pain is notoriously difficult to treat because it doesn’t result from inflammation that can be targeted by non-steroidal anti-inflammatory drugs like ibuprofen. However, whether it’s due to disease, amputation, or chemotherapy, many are turning to cannabis for the treatment of chronic neuropathic pain. Cannabis is turning out to be a promising treatment option, and its benefits have been observed in both cancer and non-cancer-related forms of neuropathic pain across rodent models and human clinical studies.

CBD-rich cannabis is protective against the development of chemotherapy-induced pain through activating serotonin receptors. Importantly, CBD is protective without impairing the effectiveness of the chemotherapy drug to destroy the cancer, making it a potentially promising prophylactic strategy for chemotherapy patients.

Sciatica is an example of a non-chemotherapy type of pain in which there’s a pinching of the sciatic nerve that causes pain in the lower back and down the leg. In sciatica, there’s an increase in CB1 receptors, that when activated, reduce pain. The common benefits of activating CB1 receptors in both chemotherapy and non-chemotherapy types of neuropathic pain suggest that cannabis’ can relieve neuropathic pain by weakening the strength of pain signals in the spinal cord and their processing in the brain. Like with nociceptive pain, over-activation of CB1 receptors with THC can eventually lead to weaker effects. Therefore, balanced THC and CBD cannabis would be more efficacious in the long-term.

Cannabis and Central Pain

Central pain has recently emerged as a catch-all term for types of pain that arise from dysfunction to the nervous system. While sometimes central pain can result from injury, it often arises in the absence of any known cause. As a result, it can be particularly hard to treat. Fibromyalgia is a classic example of central pain which arises from dysfunction in the way pain signals make their way to the brain and are processed. Like other types of central pain, the origin of fibromyalgia is largely unknown.

Because of the diversity in central pain, there are few studies investigating the benefits of cannabis in this pain category. However, the most well-established benefits of cannabis in treating central pain is for fibromyalgia. In a study of 26 fibromyalgia patients, all reported benefits from cannabis use and half stopped taking their other medications. This suggests that cannabis can provide much-needed relief for those with fibromyalgia and possibly other central pain conditions of unknown origin.

Research Takeaways

An increasing number of studies are demonstrating that cannabis is an effective pain treatment with fewer side effects than many alternatives. However, some reports still claim only “weak” evidence for cannabis’ pain-relieving benefits. Some of these negative effects may stem from the use of high-THC/low-CBD cannabis strains, which are known to induce more adverse side effects and weaken in efficacy with tolerance development.

While high-THC products may be effective pain relievers initially, they don’t represent an optimal pain relief strategy. Instead, consider balanced THC/CBD products, or CBD-rich products as they may provide better long-term treatment for chronic pain conditions.

Lead image: GeorgeRudy/iStock

4 part series

Josh Kaplan Josh Kaplan, Ph.D., is an Assistant Professor of Behavioral Neuroscience at Western Washington University. He is a passionate science writer, educator, and runs a laboratory that researches cannabis' developmental and therapeutic effects. View Josh Kaplan's articles