“Headache disorders are common, debilitating, and, in many cases, inadequately managed by existing treatments. Although clinical trials of cannabis for neuropathic pain have shown promising results, there has been limited research on its use, specifically for headache disorders. This review considers historical prescription practices, summarizes the existing reports on the use of cannabis for headache, and examines the preclinical literature exploring the role of exogenous and endogenous cannabinoids to alter headache pathophysiology. Currently, there is not enough evidence from well-designed clinical trials to support the use of cannabis for headache, but there are sufficient anecdotal and preliminary results, as well as plausible neurobiological mechanisms, to warrant properly designed clinical trials. Such trials are needed to determine short- and long-term efficacy for specific headache types, compatibility with existing treatments, optimal administration practices, as well as potential risks.” https://www.ncbi.nlm.nih.gov/pubmed/28861505

“Preclinical studies examining the role of the endocannabinoid system in migraine pathogenesis also suggest a potential therapeutic value for cannabis in the treatment of headache. It has been postulated that a general deficiency in endocannabinoid tone could underlie headache disorders.” http://online.liebertpub.com/doi/10.1089/can.2016.0033