Seppala, E., Nitschke, E., Tudorascu, D., et al. (2014). Breathing-Based Meditation Decreases Posttraumatic Stress Disorder Symptoms in U.S. Military Veterans: A Randomized Controlled Longitudinal Study. Journal of Traumatic Stress. 27: 397-405.
The authors studied the effect of meditation-based interventions on veterans with posttraumatic stress disorder. They found that those in the "active" group reported better results than participants in the control group.