Cannabis has been cultivated as an elixir for pain since as far back as 2000 years BCE. Amid increasing reports of psychosis, addiction, and other adverse effects the therapeutic use of smoked cannabis in the United States waned in the late 1930s, as a result of the Marihuana Tax Act and subsequent legislative measures, which posed nearly insurmountable obstacles for doctors. The past decade has, however, seen a resurgence in the interest in cannabinoids for alleviating pain, with the identification of at least two subtypes of cannabinoid receptors, and myriad clinical studies examining the effectiveness of tetrahydrocannabinol derivatives for acute pain, pain caused by chronic non-malignant disease, and pain from cancer. Evidence of the effectiveness of cannabinoids is strong for treating cancer, central pain, and spasticity related pain; the evidence is mixed for treating acute pain and weak for treating peripheral neuropathic pain.

In the accompanying paper, Frank and colleagues report the results of a randomised crossover controlled trial comparing the effectiveness of dihydrocodeine with the synthetic cannabinoid nabilone.1 The trial studied 96 patients with diverse neuropathic pain conditions. …