While these treatments help many patients, nightmares often continue even after other symptoms improve. By the end of the trial, people taking dronabinol reported much greater improvement than those taking the placebo. More than one-third of patients taking dronabinol said their nightmares disappeared completely, while another one-fifth reported that their nightmares were reduced by at least half. Study review and analysis: This randomized, double-blind, placebo-controlled trial provides strong evidence that dronabinol can reduce PTSD-related nightmares. The findings suggest the medicine could become an important option for patients whose nightmares do not respond to current treatments.