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Mil Med. 2018 Nov 1;183(11-12):e359-e363. doi: 10.1093/milmed/usy045.

Psychological Flexibility and Set-Shifting Among Veterans Participating in a Yoga Program: A Pilot Study.

Author information

War Related Illness and Injury Study Center, VA Palo Alto Heath Care System, U.S. Department of Veterans Affairs, 3801 Miranda Avenue, Palo Alto, CA.
Stanford University, Department of Psychiatry and Behavioral Sciences, 401 Quarry Road, Stanford, CA.
National Center for PTSD, U.S. Department of Veterans Affairs, 795 Willow Road, Menlo Park, CA.



Trauma-focused psychotherapies do not meet the needs of all veterans. Yoga shows some potential in reducing stress and perhaps even PTSD in veterans, although little is understood about the mechanisms of action. This study identifies preliminary correlates of change in PTSD and perceived stress for veterans participating in yoga.

Materials and methods:

Nine veterans (seven males and two females) were recruited from an existing clinical yoga program and observed over 16 wk. Severity of PTSD symptoms (PCL-5) and perceived stress (PSS-10) were collected at baseline and weeks 4, 6, 8, and 16. Psychological flexibility (AAQ-II) and set-shifting (ratio of trail making test A to B) were collected at baseline and at week 6. Subjects attended yoga sessions freely, ranging from 1 to 23 classes over the 16 weeks. The Stanford University Institutional Review Board approved this research protocol.


Self-reported PTSD symptoms significantly reduced while perceived stress did not. Lower baseline set-shifting predicted greater improvements in PTSD between baseline and 4 weeks; early improvements in set-shifting predicted overall reduction in PTSD. Greater psychological flexibility was associated with lower PTSD and perceived stress; more yoga practice, before and during the study, was associated with greater psychological flexibility. Other predictors were not supported.


In a small uncontrolled sample, psychological flexibility and set-shifting predicted changes in PTSD symptoms in veterans participating in a clinical yoga program, which supports findings from prior research. Future research should include an active comparison group and record frequency of yoga practiced outside formal sessions.


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