Editorial

Cannabis for chronic pain: Not a simple solution

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The narrative review by Modesto-Lowe et al1 in this issue on the potential therapeutic use of cannabis for peripheral neuropathy is only the latest in a vogue string of examinations on how medical marijuana may be used to manage complex conditions. While the authors should be lauded for acknowledging that the role of cannabis in treating peripheral neuropathy is far from settled (“the unknown” in their title), the high stakes involved warrant even more stringent scrutiny than they suggest.

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We are in the midst of an epidemic of chronic opioid use with massive repercussions, and it did not start overnight. Mounting calls for liberalizing narcotic use across a broad range of pain conditions accumulated gradually during the patient-advocacy era of the 1990s, with supporting “evidence” coming mostly from small uncontrolled studies, anecdotal reports, and industry pressure.2 Although cannabis and opioids are not interchangeable, we should be cautious about concluding that cannabis is effective and that it should be used to treat chronic pain.

CHRONIC PAIN IS COMPLICATED

Peripheral neuropathy, by definition, is a chronic pain condition. Unlike acute pain, chronic pain is characterized by biologic, psychologic, and social complexities that require nuance to manage and study.

Such nuance is lacking in most recent reviews of the medical use of cannabis. The conditions in question are often studied as if they were transient and acute, eg, employing short-term studies and rudimentary measures such as numeric pain-rating scales or other snapshots of pain intensity. Results of these shortsighted assessments are impossible to extrapolate to long-term outcomes.

Whether cannabis therapy for chronic pain conditions is sustainable remains to be seen. Outcomes in chronic pain should not be defined simply by pain reduction, but by other dimensions such as changes in pain-related disability and quality of life, development of pharmacologic tolerance or dependence, adverse effects, and other “collateral damage.” We are far from understanding these issues, which require highly controlled and regulated longitudinal studies.

A recent Cochrane review3 of the efficacy of cannabis-based medicines for chronic neuropathic pain found that harms might outweigh the benefits. The quality of evidence was rated as very low to moderate; the reviewers cited small sample sizes and exclusion of important subgroups of patients (eg, those with substance abuse or other psychiatric comorbidities). Such exclusions are the crux of a major problem with cannabis research: studies are not naturalistic. The gritty reality of chronic pain management is paramount, and failing to consider the high-risk biopsychosocial factors typical of patients with chronic pain is naïve and, frankly, dangerous.

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Correction: Men’s health 2018

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