Please use this link to access this publication. Abstract Objective Cannabidiol (CBD) has been shown to reduce seizures among patients with refractory epilepsies of various etiologies in recent clinical trials and an expanded access program (EAP). Most studies report efficacy over short time periods (<1 year), with little published on longer term efficacy. Here, we investigate the efficacy of CBD for a treatment period of up to 60 months (median = 45.5 months). Methods We conducted a retrospective review of patient-reported seizure logs and medical records for 54 subjects with refractory epilepsy who enrolled in the Massachusetts General Hospital's open-label EAP for CBD as...