Measuring the Effectiveness of Stress Prevention Programs in Military Personnel

Andrea H. Taylor and Sae Schatz

Institute for Simulation and Training, University of Central Florida. 3100 Technology Parkway, Orlando, FL 32826 {ATaylor,SSchatz}@ist.ucf.edu

Abstract. The effects of stress on military personnel are a pervasive concern. To mitigate stress’s negative impacts, Defense agencies employ stress inoculation training and, more recently, have begun to provide stress resilience instruction. However, such pre-deployment programs suffer from measurement limitations, rendering their assessment difficult. Novel application of objective, individual, repeated measures, conducted under realistically stressful settings, may help address this gap. Towards that end, we reviewed common neurophysiological techniques and examined their usefulness for measuring stress reactions. These techniques include: 1) cortisol in the blood or saliva, 2) adrenaline in the blood or urine, 3) skin conductivity, 4) EEG, 5) Skin conductance, and 6) Heart rate.

Keywords: Stress, Training, Resilience, Inoculation, Physiological Measurement.

1 Introduction

Stress in the military population is a pervasive concern that grows dramatically in times of combat. Mental health disorders are the second leading cause for hospital admissions in military members [1], and exposure to extreme stressors can lead to any number of mental health disorders, including Post Traumatic Stress Disorder (PTSD). For example, a recent Mental Health Advisory Team study [2] revealed that approximately 23% of Soldiers in Iraq reported moderate or severe levels of stress, with a total of 7.3% of Soldiers testing positive for anxiety, 6.9% for depression, and 15.2% for PTSD. In addition to potential chronic health effects (such as anxiety, depression, and PTSD), stress can also significantly decrease operational performance. Following the traditional inverted-U model of arousal, at low levels of physiological arousal, stimulation generally facilitates performance and, complementarily, at higher levels of physiological arousal, stimulation degrades performance. Extreme physiological arousal causes the suppression of cognitive and physiological resources [3], which greatly affects verbal, perceptual, and motor performance [4]. The military currently utilizes several programs to evaluate and treat stress-related mental health issues. The majority of these efforts entail post-deployment treatment rather than pre-deployment prevention. However, post-deployment treatment has not been shown to substantially reduce chronic disorders (e.g., [5], [6]) or improve future

D.D. Schmorrow and C.M. Fidopiastis (Eds.): FAC 2011, HCII 2011, LNAI 6780, pp. 636–646, 2011. © Springer-Verlag Berlin Heidelberg 2011 Measuring the Effectiveness of Stress Prevention Programs in Military Personnel 637 operational performance [7] although they do demonstrate limited positive effects regarding self-reported openness to, and perceptions of, mental health treatment (e.g., [8]). To address these limitations, pre-deployment prevention programs may be a viable addition to post-deployment treatment approaches. Military personnel already received some pre-deployment stress inoculation training, and in the last decade, the Services have more formally emphasized both inoculation and resilience training. However, due to measurement limitations, assessment of these pre-deployment efforts is difficult. To address this, we suggest that novel application of objective, individual, repeated measures, conducted under realistically stressful settings, are necessary to validate contemporary military stress prevention efforts.

2 Stress Prevention Techniques

The two primary stress-prevention efforts are resilience and inoculation training. Stress resilience training aims to teach stress management techniques, and inoculation aims to build stress tolerance through exposure. In this paper, we detail the strengths and weaknesses of available measurement techniques for these two approaches, and we offer suggestions for improving their use in military stress-prevention training programs.

2.1 Resilience Training

Resilience training (i.e., the instruction of stress coping mechanisms while in a non- stressful setting) has been shown to reduce subjective stress assessments and increase performance of participants—at least in highly controlled settings [9], [10]. Over the last decade, the Services have expanded their efforts to support stress training [11]. For example, the Army’s Resilience Training Program (formerly “Battlemind” training) is a standard, one hour pre-deployment briefing that covers basic signs and symptoms of post-deployment mental illness and encourages family members to support treatment [12]. Additionally, the U.S. Military Academy at West Point incorporates the Performance Enhancement Program. This year-long program integrates systematic psychological training into regular coursework to build mental and emotional strength, in order to maximize combat skills performance [13]. The program expanded in 2007, having now established sites at eight U.S. Army bases. To date, military resilience programs have demonstrated limited effectiveness (e.g., [14], [15]). While the programs themselves may truly be effective, measurement approaches have difficulty quantifying operational outcomes for several reasons. First, most studies focus on a single performance evaluation or post- training assessment to determine outcome effectiveness. Second, the majority of resilience training studies fail to screen participants for potential mediating variables such as previous exposure to stress reduction skills or clinical anxiety symptoms [16], [17]. Finally, it is difficult to measure the ecological validity toward military efforts, as the established laboratory measurement techniques show questionable effectiveness in operational contexts. 638 A.H. Taylor and S. Schatz

2.2 Stress Inoculation

Inoculation training involves the presentation of high-intensity situations to trainees in order to increase their stress tolerance through exposure [18]. The Navy’s SERE exemplifies this type of tolerance-building training. For instance, the military requires military personnel who may be captured to undergo SERE training, which provides a uniquely realistic training environment. SERE includes classroom instruction, field training, and a period of confinement in a Resistance Training Laboratory. This captivity scenario is intended to accurately portray an environment of extreme stress, and its ultimate goal is to inoculate war fighters to against negative stress effects and improve their performance in live field situations [19], [20]. However, as with resilience training, several problems exist with traditional inoculation training assessment, including lack of evaluation in non-clinical environments, lack of utilization of objective stress measures, use of non-standardized training guidelines, and lack of repeated acute stress measurement. In addition, the vast majority of traditional stress inoculation studies are performed using clinically anxious participants and one-on-one training with mental health professional throughout multiple sessions [21], [22]. Even when these studies are performed in the field, inoculation training effectiveness is tested under minimally stressful conditions such as test anxiety [23], [24], dental procedures [25], [26], and speech anxiety [27], [28].

3 Stress Measurement Tools

As discussed in the previous section, although some data have been collected, measurements used to assess stress tolerance training have produced ambiguous results. Thus, quantifying the impact of this training has proven challenging. To address this gap in quantification, we suggest that objective, individual, repeated measures should be integrated into current assessment efforts and that these evaluations must be conducted under realistically stressful, complex conditions (i.e., not in clinical laboratories). More specifically, we suggest that the use of neurophysiological sensors may improve the measurement of this training. Toward that end, we evaluated six common neurophysiological techniques and examined their usefulness for measuring stress reactions. These techniques include: 1) cortisol in the blood or saliva, 2) adrenaline in the blood or urine, 3) skin conductivity, 4) EEG, 5) eye tracking, and 6) heart-rate monitoring. Self-report questionnaires are also briefly described as complementary tool (as well as comparative foil) that may be used in conjunction with objective stress measures.

3.1 Cortisol

The physiological relationship between cortisol (or more formally, hydrocortisone) levels and stress has been tested extensively, and cortisol is the most commonly collected biological stress marker in experimental setting. Cortisol has been significantly related to self-reported stress symptoms, in settings such as military survival school, induced social stress, and surgical operations [29], [30], [31]. Plus, cortisol is highly correlated with various general stressors, such as test-taking and Measuring the Effectiveness of Stress Prevention Programs in Military Personnel 639 public speaking [32], [33], [34], [35], [36]. In general, cortisol measurements show a correlation (R2) of .35–.50 with self-report measures of stress and a correlation of .55– .60 with heart rate. In a recent study, salivary and self-report data were collected from 25 Navy survival school students at baseline, during two stress exposure time points, and at recovery. Cortisol levels also show moderate correlations with self-reported stress responses at all time points (Adjusted R2 = .46): from baseline, through exposure, and into recovery time [37]. The popularity of cortisol measurements continues to increase as new techniques facilitate its collection. For instance, cortisol levels can be monitored via saliva swabs, a minimally intrusive way to repeatedly monitor levels. Also, because swabs can be collected systematically, data can be assessed from specific time points within the exposure period [38], [39]. Further, saliva is not considered a biohazard, enabling researchers to collect samples with minimal training and limited administrative or safety concerns [40]. This method of measurement is not without its limitations, though. Peripheral collection techniques, such as through saliva, are subject to ongoing debate regarding their external validity [41], [42], [43]. Also, the more consistently valid collection method, i.e., intravenous sampling, is logistically challenging to employ, especially in the field and blood draws, themselves, may induce stress, causing confound [44]. Finally, cortisol measures are subject to circadian fluctuations unrelated to stress, so researchers must collect several baseline samples at various times of day [45], [46] and account for this variance during analyses.

3.2 Adrenaline

A less popular, but still validated, indicator of stress is adrenaline. Adrenaline measurements are about as reliable as cortisol swabs for monitoring stress [47], [48], [49]. A study investigating stress responses induced by strenuous air-to-air combat maneuver training in Japanese Air Self-Defense students showed significantly increased adrenaline levels post-flight, compared to pre-flight [50]. Unlike cortisol, adrenaline cannot be measured via saliva collection, and instead must be collected via urine or blood [51]. While urine sampling is less invasive than intravenous sampling, it still poses difficulties for operational use, in terms of storage, transport, and participant unease. Additionally, researchers can only obtain average levels of adrenaline from urine, because levels accumulate and average-out between urinations [52]. Since adrenaline levels increase and decrease very rapidly, collecting average levels significantly weakens urine-collection’s reliability.

3.3 Skin Conductivity

Another popular measure of stress is skin conductance, or galvanic skin response (GSR). GSR has the ability to show real-time measurements throughout the entirely of stress exposure periods, and it has been shown as positively correlate with changes in other stress indicators, such as blood , heart rate, norepinephrine and epinephrine levels [53], [54], [55], [56]. Also, at baseline or at rest, GSR is not influenced by normal circulatory changes (blood pressure, heart rate) [57], [58]. 640 A.H. Taylor and S. Schatz

However, GSR measurement may prove less appropriate for field testing than other available objective measures. GSR shows high variability based on uncontrolled external factors, such as weather or room [56]. Also, GSR electrodes must be placed on the hands or fingers, and are therefore continuously invasive to tasks that involve physical elements. Possibly due to these constraints, field studies utilizing skin conductivity are virtually nonexistent. A laboratory study with Swedish military personnel showed significant differences in skin conductance between a combat-experienced group and a comparison group while viewing combat-related photos [59]. These results indicate a strong correlation between stress and skin conductance in military settings, but reiterates the difficulties of use outside a controlled lab environment.

3.4 EEG

An electroencephalogram (EEG) records electrical activity produced by neurons firing in the brain. Data are collected from electrodes placed on the scalp and these signals are commonly divided into three spectrums: Alpha, Beta, and Theta. The Alpha channel is an effective measure for minimal stress conditions (e.g., [60]); however, Alpha does not seem to strongly correlate with self-report measures of stress when higher levels of arousal are induced (e.g., [61], [62]). In general, the use of EEGs in stress measurement is still under debate, and EEG results often fail to significantly correlate with other autonomic functions (skin conductance, ECG, heart rate, etc.; [63], [64], which makes it difficult to draw reliability conclusions when monitoring multiple measures. Additionally, although technology advances in EEG collection hardware (cap, electrodes, encoder box, and wiring) have improved, EEGs are still quite invasive to participants, take approximately 30 minutes to apply, and can only tolerate being worn for short periods of time [65]. The overall use of EEG equipment is cumbersome, as the data collection hardware is limited in portability. Once data is collected, it entails expert extrapolation of raw data before analysis can begin. Finally, a fully-equipped EEG instrument costs around $80,000, which may be too expensive for many research labs [66]. Acknowledging some of these limitations, especially the need for more portable methods of data collection in field studies, one EEG research and design company assessed the utility of a mobile EEG product during Marine Corps operational training. This testing showed external validity with heart rate variability, subjective self-assessments, and performance measures [67]. Therefore, although this improved technology is not yet widely available to the research community, it appears to be rapidly approaching.

3.5 Eye Tracking

Use of eye tracking to monitor stress has also grown in popularity as this technology continues to become more user-friendly [68]. Eye tracking data can capture reliable (R2 around .70, compared to self-report), real-time measures of stress, since stress causes significant, immediate changes in pupil dilation [69]. Measuring the Effectiveness of Stress Prevention Programs in Military Personnel 641

However, use of eye-tracking for stress monitoring has been limited to the laboratory, since pupil dilation is only a reliable/valid measure of stress under very controlled conditions [69]. Also, eye-tracking hardware and software must be precisely calibrated and any movement between the participant and the eye-tracking device requires recalibration. Some researchers and eye tracking manufacturers are attempting to solve these challenges. For example, the Department of Homeland Security is utilizing mobile eye tracking technology in assessments of TSA vigilance tasks performed in virtual environments [70]. However, until eye tracking hardware technology becomes more mobile, the use of this measurement tool is impractical for field testing.

3.6 Heart-Rate Monitoring

Much like eye tracking methods, heart rate monitoring has been utilized for decades as a reliable, real-time stress indicator [71]. Heart rate is very easy and inexpensive to monitor, and is positively correlated (adjusted R2 around .25) with self-reported stress levels [72]. Again, much as eye tracking, heart rate monitoring is inappropriate for field research, as stress can only be measured while the participant is immobile. As field research incorporates rigorous physical activity, heart rate monitoring for stress indicators is impossible.

3.7 Complementary Self-report Questionnaires

Numerous self-report surveys purport to reliably measure individual stress levels. Popular examples include the State-Trait Anxiety Inventory [73], Beck Anxiety Inventory [74], Derogatis Stress Profile [75], and Perceived Stress Scale [76]. These apparatus are generally comprehensive, show adequate validity and reliability, and correlate with a variety of psychological and somatic health outcomes. Additionally, self-report questionnaires can be as brief or as robust as necessary, offer anonymity to respondents, and are relatively easy to administer in most settings. However convenient, subjective questionnaires are not necessarily useful as the sole measurement technique of resilience or inoculation training. As Shaw and colleagues eloquently explain: “Memory is fallible: when people are asked to assess the occurrence of stressful life events retrospectively, the accuracy of their recall diminishes with longer periods of assessment, so that some events may be unreported, forgotten, or denied” [77]. Additionally, individuals’ recollection of their historic stress levels is greatly influenced by their arousal at the time of questioning [78]. Nonetheless, when paired with objective measurement approaches, self-report apparatus can contribute useful insights. A study performed with 109 U.S. Army survival training students assessed self-reported stress and cortisol levels before and after training [29]. Although both measures indicated an increase in stress, the self- report data was not significantly correlated to the cortisol levels. As is a common occurrence in mental health studies in the military, participants self-reported lower stress levels than the cortisol measure suggested. Therefore, the use of two measurement techniques provided insight into participant stress that would not have been as complete with one measure. 642 A.H. Taylor and S. Schatz

4 Conclusion

By recognizing effective measurement tools, researchers may be able to provide war fighters with improved training programs to build stress tolerance and teach stress management techniques that reduce the potential for stress-related mental illness while maintaining operational performance. Based on the review of resilience and inoculation measurement techniques, practices can be recommended in terms of evaluating stress-prevention programs (see Table 1). It appears that a combination of urinary cortisol, multiple self-report measures, and EEG would provide researchers with a much more complete picture when assessing the effectiveness of pre- deployment stress-training programs. These measurement tools are capable of providing objective, acute data at multiple time points, and can be utilized in a field- training environment. These recommendations could be used to make up a systemized measurement technique to be integrated into military stress-prevention training.

Table 1. Summary of measures’ key characteristics

Measure Ease of Use Reliability* Intrusiveness Expense (in field) (R2) Cortisol in saliva + + + ~.43 / $$ Cortisol in blood + ~.51 / / / $$$ Adrenaline in urine + + ~.38 / / $$ Adrenaline in blood + ~.47 / / / $$$ Skin Conductivity + ~.65 / / $$ EEG + + too low to determine / / $$$ Eye tracking + ~.70 / / / $$$ Heart Rate + ~.25 (Adj. R2) / / $ Self-Report Apparatus + + + ~.80 / / $ A heuristic summary based upon the authors’ interpretation of common contemporary stress measures. Under “ease of use,” + indicates difficult of use, ++ indicates neutral, +++ indicates relatively convenient to use. Under “invasiveness” / indicates limited invasiveness, // indicates moderate invasiveness, /// indicates extreme invasiveness. Under “expense,” $ indicates relatively inexpensive approaches, $$ indicates more expensive tools, $$$ indicates especially monetarily expensive tools to acquire/employ. * Reliability estimates based upon comparisons with self-report apparatus; see text above for specific details and citations.

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