Part II — In a Bad Way: Pain, Cannabis and Opioids – Types of Pain and How Cannabis Works to Relieve It

People hurt in different ways and from different causes so I’ll start with a brief primer on the three basic types of pain – nociceptive, neuropathic and central.

Inflammatory Pain (Nociceptive)

Think of nociceptive pain as the garden variety inflammatory pain that every weekend warrior has experienced. It can be sharp, achy, tender or throbbing depending upon the tissue damage location and extent. Before you reach for the Advil and an ice pack, your tissues get busy recruiting inflammatory and immune cells to repair the damage.  In turn, the cells release proteins and chemicals that activate receptors on nerves that make their way into the spinal cord and up to the brain.  When the brain gets involved, the sensation of pain begins.

Neuropathic Pain

Neuropathic pain is a different animal. As its name suggests, neuropathic pain arises from damage to the body’s nervous system.  It’s more common than you think, affecting some seven to ten percent of the population.  Nerve pain can result from a forceful injury like pinching or stabbing.   But more patients know neuropathic pain from underlying diseases such as Parkinson’s disease, diabetes, shingles and multiple sclerosis.

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Central Pain

Central pain is trickier to describe and the hardest to treat.  It’s defined as a neurological condition caused by damage to or dysfunction of the central nervous system (CNS), which includes the brain, brainstem and spinal cord. It can be caused by disease, tumors, or by brain or spinal cord trauma.  Because of the variety of causes, central pain differs widely from patient to patient.  It may affect a large portion of the body or may be more restricted to specific areas, such as hands or feet.

When I worked in brain injury rehabilitation, central pain for those we cared for was common and unrelenting, made worse by touch, movement, emotions, and temperature changes.  Patients would tell me that they felt “pins and needles” or a burning sensation in their hands or feet that would make moving, even in bed, terribly difficult.   Sometimes central pain results from an injury but it can often arise in the absence of any known cause.  Fibromyalgia, a classic example of central pain, comes from dysfunction in the way pain signals make their way to the brain and are processed.

How Cannabis Spells Relief

The Downside of NSAIDS

Although cannabis is fairly well-known as a pain relief treatment, it is rarely the first drug that a patient takes to mitigate pain.  Most of us shop for one of the abundant drugstore varieties of Ibuprofen and Naproxen known as nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDS inhibit pain by addressing local tissue inflammation, blocking an enzyme called cyclooxygenase (COX), which is required to make the blood vessels dilate.  They can be used daily for prolonged periods to manage inflammatory conditions, whether it’s due to arthritis or a sprained ankle, but they are not without their side effects when used frequently.    One patient told me that she ended up in the ER after taking a nightly dose of Ibuprofen to help her aches and pains.  Eventually this led to a nasty bleed in the gastro-intestinal tract and a stern warning from her physician to curb her seemingly- innocuous Advil usage immediately.

Considering Cannabis for Inflammation

Why would cannabis help diminish inflammatory pain?  For starters, cannabis turns on pain inhibition.  Both CBD and THC cannabinoids reduce the pain signals at the site of injury by blocking the inflammatory process itself.  Then, as pain signals try to make their way up the spinal cord to the brain, THC activates the body’s built-in CB1 and CB2 cells, mitigating the body’s pain-inducing response to injury. CBD reduces inflammation by both blocking inflammatory mediators and activating the helpful repair cells known as macrophages from the pro-inflammatory type to the anti-inflammatory type.  It’s like playing a little trick on the brain by making it a little less sensitized to a process that ordinarily is hurtful.

Calming Nerve Pain with Cannabis

Neuropathic pain, on the other hand, may not respond at all to anti-inflammatory drugs so patients and their health care providers commonly struggle to find a safe and effective form of relief – usually in the form of prescriptive drugs like anti-depressants and anti-convulsants.  But again, cannabis comes to the rescue of many who suffer nerve-related pain by turning on cannabinoid receptors in the peripheral nerves.   A good example is sciatica, a painful condition in which the pinching of the sciatic nerve starts a chain reaction of pain radiating from the lower back down the leg.   Cannabis works for a sciatica patient by increasing the CB1 receptors along the spinal cord pathway which in turn reduce pain.  Relieving neuropathic pain by weakening the strength of pain signals in the spinal cord and how they are processed in the brain is powerful since is can address such a vexing and wide-ranging spate of diseases and injuries.  Just ask anyone who’s had a bad case of shingles.

Central Pain Case in Point: Fibromyalgia

In the area of central pain, the most intense subject of research is how cannabis might help patients with fibromyalgia, a complicated and often misdiagnosed disease.  Affecting some 10 million people in the U.S. alone, fibromyalgia is a common condition that affects the bones and muscles, causing chronic joint pain and fatigue.   There is no cure for fibromyalgia and no direct cause is known although certain factors – such as genetics and stress – may act as triggers for the disease.

Reviews in the scientific literature for using cannabis to treat fibromyalgia are mixed. I found only one double-blind, placebo-controlled randomized, controlled trial which used a synthetic form of cannabinoid and concluded that it was a “beneficial, well-tolerated treatment option” that could be a viable adjunct to other therapies.  But other anecdotal studies favored botanical cannabis – in one such study, over half of the participants reported that they were able to stop taking prescription drugs entirely.

Driven to Distraction – Another Way Cannabis Curbs Pain

Relieving hard-to-treat pain, be it neuropathic or central, might result also from an aspect of cannabis consumption that is hidden in plain sight.  When individuals use cannabis, the parts of their brains associated with reward and motivation are more active. In turn, the brain releases more rewards-driven neurotransmitters than usual, releasing a sense of euphoria. Cannabis also typically makes people more easily distracted, because their short-term memory abilities get temporarily compromised. It shouldn’t surprise anyone that boosting mood and creating distraction can bring about pain relief.

Some Practical Considerations

Although cannabis is certainly a promising adjunct to the vast playing field of pain management, some caveats bear mentioning.  Every article I’ve read on cannabis and pain concludes that more research is necessary to determine what particular strains work for specific conditions.   How cannabis is ingested matters too – drops, vapors and edibles behave completely differently from person to person.

And of course we’ll have to figure out how to determine dosage and the proper ratios of the various cannabinoid compounds.   Research writers are quick to warn of adverse side effects and a weakness in efficacy as tolerance develops, especially when using high-THC/low-CBD cannabis strains.

Using cannabis in medicine, especially in pain management, is not without complications but I’m hopeful that we will learn from our past mistakes and resolve to do better – most pointedly from the observed success of decreasing opioid deaths in legalized medical cannabis states.   The slow climb to identifying specific treatment plans for medical cannabis will only come with more trial and error studies as additional researchers chime in.  Sometimes my head hurts from grappling with the learning curve of a treatment laden with possibilities but with so many unanswerable questions at the present moment.   But that’s one pain I’m willing to weather.