While this study did not show any statistically significant difference between the cannabis-use group and the placebo group, it did conclude that its use did not raise any safety concerns.
The study by The Multidisciplinary Association of Psychedelic Studies was the first FDA-approved randomized placebo-controlled trial comparing the therapeutic potential of varying ratios of THC and CBD for treating symptoms of PTSD.
One of the drawbacks is that the patients had to use cannabis from the US government facility in Mississippi that had a maximum THC content of 9%, which is MUCH lower than most of the cannabis in state-legal markets these days. “The difference between anecdotal reports and these results may be the quality of the marijuana,” one researcher admitted.
A summary article from LA Weekly about the study is here.