English: Autonomic nervous system Dansk: Auton...

English: Autonomic nervous system Dansk: Autonome nervesystem. (Photo credit: Wikipedia)

What do a 2,500 year-old monk and a modern-day ninth-generation military woman have in common? Besides some common thread of humanity, on the surface it may not seem like much.

Like the military, mindfulness has a deep-seated history. Rooted in Buddhist psychology, mindfulness made its way into modern-day American society in various forms in the 1960s and 1970s when Eastern teachers began settling in the United States, and westerners who had studied in the East brought what they had learned back to the States. Jon Kabat-Zinn began teaching a secularized mindfulness-based stress reduction course at the University of Massachusetts Medical School in the late 1970s, which importantly, was adapted for clinical contexts and could be studied. Over the past 35 years, this and other mindfulness-based interventions have begun to build an evidence base that suggests utility in disorders ranging from anxiety and depression to smoking and other substance use disorders (13). Over the past decade, some of the first “contemplative neuroscience” studies have emerged in the literature and begun unpacking how mindfulness might affect not only our brains but our (related) stress physiology (for example, in 2003, mindfulness-based stress reduction was shown to boost antibody titers to vaccine administration) (4, 5).

And now, in a study reported in this issue of the Journal, Johnson and colleagues have brought mindfulness to the military (6). This is a particularly interesting context because instead of helping a population with disorders return to health (e.g., military personnel who have developed posttraumatic stress disorder), Johnson et al. provided mindfulness training to healthy individuals to help them develop resilience. In brief, Mindfulness-Based Mind Fitness Training, which was developed specifically for military environments by Dr. Elizabeth Stanley, ninth-generation U.S. Army, combines mindfulness practice with a didactic and skills training component on autonomic nervous system regulation. In theory, this combination is supposed to train individuals to behaviorally “tune” their autonomic nervous system to be more dynamically responsive to stress. This is important because although the military uses stress inoculation training to put soldiers in real-world simulations to better prepare them for actual combat, stress inoculation does not provide recovery training—that is, how to “turn off” their nervous system once the stressor has passed; stress inoculation teaches troops to function well during stress but not how to recover to baseline afterward. Stress inoculation training also leads to decrements in cognitive functioning (e.g., working memory capacity) and even dissociation as a maladaptive coping strategy, with associated degradation in military performance (79).

Mindfulness-Based Mind Fitness Training was developed to fill this gap. By training soldiers how to monitor their own bodies for autonomic activation and to use mindful awareness to tune this activation down efficiently and appropriately, they can learn to work adaptively in situations such as stress inoculation and combat, effectively both increasing their dynamic response range and preventing them from burning out (or acting out) during prolonged stress exposure.

Stanley’s group previously published preliminary studies suggesting that this may indeed be the case. In active military cohorts who received Mindfulness-Based Mind Fitness Training before deployment, working memory capacity was preserved after deployment, and, as expected, it degraded in soldiers who did not receive the mindfulness intervention (10). In addition, perceived stress levels decreased among military cohorts who received the intervention compared with controls (11).

Johnson et al. take this one step further in this new study by examining both physiological and neural changes associated with Mindfulness-Based Mind Fitness Training. They randomly assigned 281 Marines to receive either training as usual or training as usual plus 20 hours of mindfulness training over an 8-week period during predeployment preparation. They then measured physiological markers of resilience before, during, and after a stress inoculation challenge, which consisted of real-time scenarios of counterinsurgency operations (e.g., village patrol, complex ambush). In a subset of individuals (20 from each group), they also used functional MRI to assess neural response to an emotional face processing task in brain regions associated with interoceptive awareness (e.g., the insula) and attentional control (e.g., the anterior cingulate cortex).

Marines who received the mindfulness training intervention attended a majority of the training sessions (92%), which may not be surprising given the context, and they reported a mean total of about 2.5 hours of practice outside of the classroom over the 8-week period. Marines who received the intervention showed a significant increase in heart rate in anticipation to the stress challenge, which was nonsignificantly higher during the challenge. Interestingly, their rate of recovery was significantly faster than the control group’s. Breathing rate recovery was similarly faster in the intervention group relative to the control group. The intervention group also showed lower concentrations of neuropeptide Y (a marker of autonomic system activation) after stress inoculation, which was significantly correlated with heart rate during response and recovery periods (R2=0.25 during both periods). However, the authors did not find similar correlations for epinephrine levels. Also, Marines who received mindfulness training showed less activation to emotional faces in the right insula and the anterior cingulate cortex. Changes in the right anterior insula were correlated with changes in a self-reported measure, the Response to Stressful Experiences Scale, from before mindfulness training to after the stress inoculation challenge.

This study is noteworthy for its taking place in an active military training setting, the use of stress inoculation training as a real-world stressor (as compared with bringing participants into a lab), the linkage of physiological markers, and a grounded theoretical basis for what the mindfulness training intervention would target. What is less clear is how exactly the changes in brain activity line up. One might hypothesize that these should correlate with the physiological markers as well, if indeed individuals are processing interoceptive stimuli, as suggested. Furthermore, the authors focused their neuroimaging analyses on brain regions defined a priori, which is good for testing specific hypotheses but may miss potentially relevant targets. For example, the dorsal anterior cingulate has been shown to regulate the posterior cingulate cortex, which correlates with improved performance (12); these regions have been shown to be functionally coupled in experienced meditators (13). Additionally, the lack of an active control group raises the question of whether the addition of 20 hours of group training plus homework could nonspecifically help individuals become more cohesive or more bonded within their group, yielding similar changes in physiology.

Given the promising results of this study, what is next for this field? A dizzying array of mindfulness-based interventions are being developed and rolled out at present, likely in response to the pervasive nature of many disorders, the need for improved treatments, the current popularity of mindfulness among the public (in 2007, 9.4% of the U.S. population reported using meditation in the past year [14]), and the growing evidence base for such treatments. Only a few of these modalities have been standardized (e.g., mindfulness-based stress reduction and mindfulness-based cognitive therapy for depression). As exemplified by Crane et al., it is critical that standards for maintaining fidelity and competency are developed and utilized (15, 16). This will help researchers isolate variables to more clearly establish efficacy and mechanisms in an already inherently difficult-to-study intervention (for example, it is hard to tell if someone is meditating just by looking at them). Standards of this type, like those governing the chemical composition of medications, will also help protect our patients by ensuring that they are getting the evidence-based mindfulness intervention that they signed up for.

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