A pilot study involving 41 military veterans and 5 active-duty soldiers diagnosed with clinical levels of PTSD has found that one month of transcendental meditation produced dramatic benefits, with 37 (80%) having their symptoms reduced to below the clinical level, and 40 having a clinically significant decrease of more than 10 points.
A test 90 days later also showed that PTSD symptoms continued to improve, and a further three individuals had dropped to below the clinical level.
The participants learned the standard Transcendental Meditation technique, which is practiced 20 minutes twice a day. Those who practiced twice a day had greater benefits than those who practiced once a day.
The study follows on from two earlier studies involving Congolese refugees, who found a significant benefit after just 10 days of Transcendental Meditation.
Note that this is only a preliminary study, with no controls, and the participants were self-selected, responding to media advertising (89 responded — only those with clinical levels of PTSD were included in the study). However, the results certainly appear dramatic, and previous research has shown that Transcendental Meditation has a positive benefit for many of the conditions associated with PTSD, such as high anxiety, insomnia, depression, and high blood pressure.
Full text of the paper is available at https://academic.oup.com/milmed/article/183/1-2/e144/4781643