Medical Cannabis for the Treatment of Chronic Pain: A Review of Clinical Effectiveness and Guidelines

Chronic pain is defined as pain that persists for more than three months.¹ It may present as headache, musculoskeletal pain, visceral pain, neuropathic pain, pain arising from rheumatic disease, and cancer pain.¹ Chronic pain is a global problem.² In Canada, approximately 25% adults have a chronic pain condition.² The prevalence estimates of chronic pain are likely to vary depending on the sample population surveyed, and the assessment method.³ Costs associated with chronic pain include both direct and indirect costs. It is estimated that in Canada the annual direct cost to the healthcare system is over six billion dollars and the annual indirect cost due to job loss and sick days is over 37 billion dollars.² Chronic pain is a problem for the individual suffering, and also a societal burden. Therapies for management for chronic pain include several pharmacological agents (such as tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and opioid analgesics).^4,5 However, these medications offer limited pain relief and are associated with adverse effects.^4,5 There is increasing interest in the use of cannabis-based medicines. Cannabis-based medicines contain cannabinoids derived from the cannabis plant, including delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), or a combination of THC and CBD⁶. There is, however, uncertainty and controversy regarding the use of cannabis-based medicines for the management of chronic pain.⁷ The purpose of this report is to review the clinical effectiveness of medical cannabis for the treatment of chronic pain. Additionally, this report aims to review the evidence-based guidelines regarding associated with the use of medical cannabis for the treatment of chronic pain.