Abstract Introduction: Given the increasing availability and use of cannabis among individuals with post-traumatic stress disorder (PTSD) and the addition of PTSD as an eligible diagnosis in several U.S. medical cannabis programs, the efficacy of dispensary-obtained cannabis needs to be thoroughly examined. Materials and Methods: This prospective study assessed PTSD symptoms and functioning every 3 months over the course of a year in two samples of participants diagnosed with PTSD: (1) those with PTSD using dispensary-obtained cannabis (cannabis users) and (2) those with PTSD, who do not use cannabis (controls). Linear mixed-effects models and generalized estimating equations tested whether trajectories of symptoms differed between the two...