Marijuana for Some Types of Pain, but Not Others

Marijuana can effectively reduce the experience of only certain types of pain. Why? All pain is not the same. No single drug can adequately reduce the experience of all types of pain. We treat severe pain associated with broken bones and cancer with prescription opiates. We treat minor aches and pains with over-the-counter drugs such as acetaminophen and ibuprofen (i.e., Tylenol and Advil). Acetaminophen and ibuprofen are capable of reducing the brain’s subjective experience of pain by enhancing the action of the endogenous marijuana neurotransmitter known as anandamide. Once anandamide is released inside the brain specific enzymes quickly inactivate it. One of these enzymes is cyclooxygenase (COX). Ibuprofen and acetaminophen inhibit the action of COX. Thus, taking these over-the-counter drugs enhances the actions of anandamide and thereby mimic the effects of marijuana in your brain. The marijuana plant does not contain anandamide and no component of the plant acts upon the COX enzyme. Essentially, marijuana reduces the brain’s subjective experience of pain my mimicking the actions of anandamide.

Not all types of pain are affected equally by marijuana. The National Academies of Sciences, Engineering, and Medicine have concluded that marijuana (the entire plant, not some individual component) is effective for the treatment of chronic pain in adults. Only the entire plant, containing over one hundred different potentially bioactive molecules, produces benefit; the individual molecules that have been studied are not as effective when administered alone. Unfortunately, the cannabis plant that is most commonly available for use today has been bred to contain high levels of specific molecules, such as THC, CBD, THCA, etc. Unfortunately, patients with chronic pain do not find significant relief with these current formulations. Thus, you are likely to see individual accounts on the internet that marijuana failed to relieve their pain.

Current evidence supports the safety and efficacy of short-term, low-dose cannabis vaporization and oral mucosal delivery for the treatment of neuropathic pain in patients with Multiple Sclerosis (MS) and in patients with migraine headaches. Although the best dose remains uncertain, most participants used between 20 and 40 mg of THC a day in divided doses. Serious adverse events are rare and cannabis products are generally well-tolerated. In contrast, there is little evidence that medical cannabis is effective for pain associated with arthritis, postoperative pain, back pain, or severe trauma-related pains. Additional well-controlled studies are still needed. There have been no reliable clinical studies evaluating pure CBD in headache or chronic pain disorders; however, CBD has potent anti-inflammatory properties that should be investigated further. Most migraineurs in these studies preferred strains that were high in THC and low in CBD. Claims on the internet that CBD oil treats pain are simply not supported by current evidence.

© Gary L. Wenk, Ph.D. is the author of The Brain: What Everyone Needs to Know (2017) and Your Brain on Food, 2nd Edition, (2015, Oxford University Press).