Summary by Lynn Stoller, M.S., OTR/L, C-IAYT, SIPT-cert.

In 2008, while teaching yoga during his off-duty hours as a flight instructor on the Kirkuk Air Force Base in Iraq, Major Jon Greuel came up with idea of doing a study to gather empirical evidence of its effectiveness in reducing the symptoms of combat stress. He even wondered if doing yoga while deployed might have potential to actually pre-empt the development of a full-blown case of PTSD. Though answering this larger question went beyond the scope of what is now referred to as the Iraq Yoga Study, the randomized controlled trial of 70 deployed U.S. military personnel that resulted from his brainstorm was a big success and paves the way for future studies.

Major Greuel ultimately reached out to Lucy Cimini, founder of Yoga Warriors, to ask if she would be interested in collaborating on the study. Lucy in turn delegated responsibility to me (her workshop co-presenter and OT Consultant and Research Coordinator at the time of the study) for forming and managing the stateside team and the writing, and so I was granted the role of Associate Investigator. Together, Lucy and I developed the treatment protocol, which consisted of treatment principles and a lesson plan. Dr. Mary Fowler served as the statistician and the late Dr. Jane Koomar, internationally renowned sensory integration expert and author, served as my professional advisor for the study. Major Greuel served as Principal Investigator and also was the yoga instructor for the study. The randomized controlled study was managed by the U.S. Army Institute of Surgical Research and was approved by the Brooke Army Medical Center.

The study produced many positive results and was subsequently published in the American Journal of Occupational Therapy. The study article is titled Effects of Sensory-Enhanced Yoga on Symptoms of Combat Stress in Deployed Military Personnel (Stoller et al, 2012) and can be found at this link:

Stoller, C. C., Greuel, J. H., Cimini, L. S., Fowler, M. S., & Koomar, J. A. (2012). Effects of sensory-enhanced yoga on symptoms of combat stress in deployed military personnel. American Journal of Occupational Therapy, 66, 59–68.doi: 10.5014/ajot.2012.001230

The objectives of the study were as follows:

  1. to examine the effects of sensory-enhanced hatha yoga on symptoms of combat stress in deployed U.S. military personnel;
  2. to compare anxiety and sensory processing in this population with stateside civilians; and
  3. to identify any correlations between measures on the State/Trait Anxiety Inventory and the Adolescent/Adult Sensory Profile.

Of the 70 participants who participated in the trial, 20 were in the Army and 50 were in the Air Force; 22 were female and 48 male. The group’s mean age was 32. Thirty-five subjects received three weeks (≥ nine sessions) of sensory-enhanced hatha yoga and 35 did not receive any form of yoga. The subjects were required to attend a minimum of two yoga sessions per week. Twenty-five of the 35 subjects met or exceeded the attendance requirements, while ten did not. The statistical findings were based on the complete treatment group, using “best practices” ITT (Intention to Treat) analysis, whether or not the subjects actually met the stated minimum treatment criteria.

We used the following three measurement tools. The first two are standardized while the third is a custom designed tool developed by the team.

● Adolescent/Adult Sensory Profile*

● State/Trait Anxiety Inventory

● Quality of Life Survey (Stoller, Greuel,& Cimini, 2009)

Following are definitions of test measures for the first two test tools:

Test Measures

Sensory Sensitivity* Represents behaviors in accordance with a low neurological threshold. Distractibility, difficulty screening stimuli, and discomfort with sensation characterize this quadrant.”
Sensation Avoiding* Counteracting a low neurological threshold, sensation avoiding includes behaviors that limit exposure to stimuli.”
Low registration* Low registration reflects responses in accordance with a high neurological threshold. This quadrant includes a disregard of or slow response to sensation.”
Sensation Seeking* Sensation seeking is a counteractive response to high neurological threshold and encompasses pleasure derived from rich sensory environments and behaviors that create sensation.”
State Anxiety “’State anxiety reflects a “transitory emotional state or condition of the human organism that is characterized by subjective, consciously perceived feelings of tension and apprehension, and heightened autonomic nervous system activity.’ State anxiety may fluctuate over time and can vary in intensity.”
Trait Anxiety Trait anxiety denotes ‘relatively stable individual differences in anxiety proneness . . .’ and refers to a general tendency to respond with anxiety to perceived threats in the environment.”

Brown, Tollefson, Dunn, Cromwell, & Filion, 2001, p. 76.

State/Trait Anxiety Inventory. Retrieved June 24, 2009, from www.

The treatment protocol consisted of a hatha yoga program that was designed to provide a therapeutic threshold of carefully selected sensory input, breathing techniques that promote calming, and a series of postures to balance the nervous system. In addition, each session had to include 2-5 positive affirmations per session, and at least 50% of the sessions needed to include an inspirational reading.

The results are summarized below.


● The treatment group showed significantly reduced state and trait anxiety as compared with the control group, despite normal pre-test scores (p < 0.001).

Sensory Processing:

● The data did not yield evidence that the sensory-enhanced yoga treatment would help to increase normalization of sensory processing.

All 6 subjects who scored high sensory sensitivity were randomized to the control group, so one would not expect to see significant normalization from the yoga program.

Correlation Results:

● A one-tailed Pearson correlation test yielded evidence of a significant positive correlation between the following five measures: state anxiety, trait anxiety, sensory sensitivity, sensory avoidance and low registration.

● Sensory seeking was negatively correlated with all measures except low registration, which was insignificant.

This correlation pattern matched the pattern of a pilot study conducted with 12 older combat veterans who were all diagnosed with PTSD (Stoller & Cimini, 2008.).

Military Test Scores as Compared to Established Norms:

The AASP results for the four quadrants- low registration, sensory sensitivity, sensory avoidance, and sensory seeking- did not provide evidence of a difference between the mean values of the deployed military personnel population and the normative civilian population.

The data from the State/Trait Anxiety Inventory did not yield evidence that either the female or male military population have higher levels of state anxiety or trait anxiety than the normative population.

A significant number of study participants had only been deployed for about one month, but we were unsuccessful in gathering reliable data on length of deployment.

Quality of Life Survey:

Treatment subjects showed significantly greater improvement on 16 of 18 variables on the Quality of Life Survey as compared to control.

Items reaching the .001 level of significance, showing a decrease over the course of the study and thus indicating improvement in functioning, were “having difficulty concentrating” “feeling irritable”, “having difficulty performing daily tasks”, “avoiding socializing”, “not feeling real interested in things” and “experiencing feelings of boredom”.

Items reaching the .01 level of significance, indicating improvement in functioning, were “having difficulty sleeping” (p = 0.002), “feeling ‘down in the dumps’” (p= 0.002), “not attending to my self-care needs” (p = 0.002), “having outbursts of anger” (p = 0.003), “always ‘on guard’ or ‘watching my back” (p = 0.003), “experiencing feelings of loneliness” (p = 0.004); “experiencing intrusive thoughts or images” (p = 0.005); and “having bouts of sadness or crying” (p = 0.007).

Items reaching the .05 level of significance, indicating improvement in functioning, were “blaming myself for things” (p = 0.011) and “experiencing distressing ‘mini-dreams’” (p = 0.023).

Optional written comments by the yoga participants support the results of the standardized measurement tools. Fifty-four percent of the subjects reported sleep improvements either during (“fell asleep at end”) or following yoga sessions, despite environmental distractions such as gunfire or helicopter sounds. In addition, 37% of subjects commented that they felt more calm or relaxed; 26% commented on other physical benefits; and 11% reported reduced frustration/anger or better anger management.

Please refer to the original study article for discussion and more details of the study, and also feel free to contact the Sensory-Enhanced Yoga Institute® for guidance on how to incorporate sensory-enhanced yoga techniques into a yoga program or research study for self-regulation and trauma healing.