Mental health, physical symptoms and biomarkers of stress during prolonged exposure to Antarctica's extreme environment
Introduction
Adverse psychological reactions are recognized among the most serious risks posed to crew members and mission success during space flight [2,3]. Selection methods and counter measures help to reduce such risk, but even the most competent and highly-skilled individuals are susceptible to adaptation problems in extreme environments. While the reported incidence of psychological crises occurring during previous space missions is notably low [[4], [5], [6]], long-duration space exploration (LDSE) such as a Mars mission will significantly extend astronauts’ exposure to a range of extreme stressors including confinement, social isolation, microgravity, altered photoperiods, monotony of environmental stimuli, delays in communication, and limited privacy. Surprisingly little is known however, about the types of psychological reactions most likely to occur in isolated, confined, extreme (ICE) environments.
The Antarctic is regarded as an ideal analog for space because its extreme environment is characterized by numerous stressors that mirror those present during LDSE. In addition to small crews and limited communication during Antarctic winter months, the environment offers little sensory stimulation and extended periods of darkness and harsh weather conditions restrict outdoor activity. Evacuation is difficult if not impossible. Previously, several classifications of psychological maladjustment have been proposed to facilitate risk identification and early intervention in polar settings [[7], [8], [9]] but none have received wide-spread adoption. As a result, an array of measures, constructs and symptoms have been examined, most often with a central focus on negative mood [2]. Although several investigations have reported overall low rates of negative mood among polar expedition and station crews [[10], [11], [12], [13]], a recent meta-analysis of data from 21 studies reveals negative mood to fluctuate considerably across the course of Antarctic winter-over [14]. Likewise, extended Antarctic stays negatively impact positive emotional states [15] and coping [16] over time. These results make clear a need to assess psychological functioning repeatedly across multiple time points using a broad framework for understanding psychological adaptation in ICE environments.
Recently, our group developed a self-report measure of psychological reactions for use in ICE environments, the Mental Health Checklist (MHCL; [1]. Exploratory and confirmatory factor analyses of the original questionnaire in two community samples produced a 23-item measure with three reliable subscales: positive adaptation, poor self-regulation, and anxious apprehension. Reliability and convergent validity of the MHCL subscales were further demonstrated in a sample of 110 crew members shortly after arrival at an Antarctic station. In the current study, we examined monthly changes in these subscales in the same Antarctic cohort over the course of a winter season, as well as the extent to which several relevant, trait-based psychological constructs assessed at baseline (i.e., distress tolerance, anxiety sensitivity, and emotion dysregulation) might serve to predict end of study MHCL scores.
In addition, because emotional reactions in ICE environments might be less prognostic of mental health risk than the degree to which they can be effectively managed by the individual, we collected monthly reports of strategies used to regulate emotions. In contrast to a focus on ‘coping’ which is concerned with the reduction of negative states, emotion regulation refers to the heterogeneous set of actions that influence what emotions we have, when we have them, and how often [17]. In our study, we focused specifically on strategies used to alter the intensity and/or duration of positive emotions (i.e., happy, excited, enthused) since many of the stressors present in ICE environments (e.g., altered light-dark patterns, monotony, confinement, social isolation, circadian disruption) are known to significantly degrade positive affect/emotions [2]. Positive emotions are also known to robustly influence overall mental health and well-being (Fredrickson, 2000), yet remain understudied in ICE settings.
An additional focus of our study was on the presence of physical symptoms/complaints. Several environmental factors encountered in the Antarctic are known to produce physiological changes directly linked with mental health difficulties. For example, long-term exposure to cold temperatures produces changes in thyroid function that can cause fatigue, sluggishness, and changes in urination [18,19],;recognized symptoms of low mood/depression [9,20]. High altitudes can result in headaches, light-headedness, and cardiopulmonary symptoms including tachycardia and dyspnea [21]; known features of anxiety and panic [21,22]. Physical complaints reported by Antarctic winter-over personnel might therefore serve as ‘red flags’ for problematic changes in mental health. Findings toward this end are both limited and mixed. For example, among a 24-member Antarctic expedition crew, physical symptoms peaked at mid-winter whereas the highest levels of anxiety occurred subsequently in late winter [23]. Conversely, in another Antarctic winter-over cohort, thymic reactions (e.g., low mood) increased linearly across mission whereas somatic symptoms (e.g., fatigue, headache, etc.) showed an opposing linear decrease over time [24].
Finally, since stress hormones correspond and interact with both psychological and somatic symptoms, we examined corresponding monthly changes in salivary biomarkers of stress . We specifically focused on three indices: cortisol, dehydroepiandrosterone (DHEA), and their ratio. Whereas cortisol is recognized as a primary stress hormone and found to be hypersecreted in depressed individuals [25], DHEA is an endogenous steroid that possesses anti-glucocorticoid properties [26]. The antagonist action of DHEA to cortisol in the brain suggests that measurement of cortisol alone could provide an incomplete picture of the body's stress response [27]. Thus, we also examined cortisol:DHEA ratios, which have been found to differentiate depressed patients from healthy controls [28].
The current investigation included personnel stationed at either an inland (South Pole) or coastal (McMurdo) station during a nine-month period including winter-over. We had several specific aims. First, we examined and compared changes in monthly MHCL scores, physical symptoms, and stress biomarker levels both within and between the two stations across mission. We also examined monthly use of five specific cognitive strategies commonly used to regulate (i.e., increase or decrease) positive emotions across the mission in the full sample. Second, we examined the extent to which trait-based psychological measures assessed at baseline served to predict MHCL scores at the end-of-mission. Finally, we explored whether within-mission severity of physical symptoms, stress biomarkers, and/or emotion regulatory strategies predicted end-of-mission MHCL scores.
Section snippets
Participants
A total of 110 participants were enrolled during the nine-month study period (February through October) . At McMurdo, n = 88 personnel were enrolled and at the South Pole, n = 22 were enrolled. All on-station personnel were eligible to participate. Of the total enrolled sample, participants were predominantly white (94.5%, n = 104) males (80%, n = 88) between the ages of 22 and 70 years (M = 37.63, SD = 11.95). Characteristics of the full sample and at each station are displayed in Table 1. One
Mental health
Mean MHCL positive adaptation, poor self-regulation and anxious apprehension scores at each time point are presented in Table 3. In the full sample, participants showed a significant decrease in positive adaptation, F (1,96) = 24.48, p < .001 (η2partial = .20), and significant increase in poor self-regulation, F (1,96) = 15.00, p < .001, η2partial = .14, from baseline to the end of study. No significant changes were detected for anxious apprehension scores over time, F (1,96) = 1.72, p = .19 (η2
Discussion
As we inch closer to human exploration of the Red Planet, understanding of specific psychological reactions that could threaten a successful Mars mission remains inadequate. Albeit not a perfect analog for space, Antarctica's extreme, inhospitable environment offers an opportunity to systematically investigate the types of psychological changes that emerge in isolated, confined and extreme environments over extended periods of time. The current study examined changes in various types of mental
Conclusion
Our study provides new and interesting findings regarding mental health changes over time at two Antarctic stations with potential implications for LDSE. In all subjects, positive adaptation scores progressively decreased across the study, suggestive of increasing feelings of detachment and/or indifference over time. Conversely, poor self-regulation scores increased across the study and were predicted by co-occurring increases in the severity of physical symptoms. One particularly novel aspect
Funding
This work was supported by a grant from the U.S. National Aeronautics and Space Administration (#NNX15AC13G) awarded to the first and last authors.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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