A medication containing tetrahydrocannabinol (THC) significantly reduced the frequency and intensity of nightmares among patients with post-traumatic stress disorder (PTSD), according to a randomized clinical trial published in Nature. The 1.5-point difference between the groups was statistically significant, researchers reported, with a moderate-to-large effect size. More than one-third of patients receiving dronabinol reported experiencing no nightmares by the end of the treatment period. Adverse events were reported by 89.7% of patients receiving dronabinol and 77.1% of those receiving placebo. Five patients receiving dronabinol, or 5.7%, discontinued treatment because of adverse events, compared with six patients, or 7.2%, in the placebo group.