Abstract
Using a large-scale survey, we examined the relationship between number of deployments experienced by female spouses of active duty military members and these spouses’ perceived stress. Results suggest a nonlinear relationship such that spouses who had not experienced a deployment reported the lowest stress levels. Stress levels increase after initial deployments and decrease after approximately two deployments, which may indicate an element of resiliency that builds up as spouses acclimate to a deployment lifestyle. Stress levels again increase after several deployments, which may signify limitations to this resiliency over time. A secondary finding showed that higher levels of social support predicted lower levels of stress, above and beyond the number of deployments. This relationship between social support and stress helped explain the negative relationship between parental status and stress. That is, spouses with children may have lower stress levels due to the social network that accompanies parental status.
Military spouses have faced steady cycles of deployments and reunions in recent years as a result of the country’s participation in the longest US military operation since the Vietnam War. Recurrent deployment cycles have the potential to strain military marriages, as Service members and their spouses deal with long, frequent, and often extended deployments. Research has found that deployment-related stress can negatively impact the mental and physical health of military spouses and the military family as a whole. 1 It would logically follow that the cumulative effects of multiple deployments would exacerbate this impact; yet, there is little empirical work evaluating this. Using data from the 2008 Survey of Active Duty Military Spouses (2008 ADSS), we aim to investigate the effect of multiple deployments on stress levels of military spouses. Specifically, we will use multiple regression to test if the relationship between multiple deployments on stress levels is linear, or if there is curvilinear trend. We will also examine the role of social support on this relationship.
Deployments and Well-being
During periods of high operational tempo, Service members can receive notification of their next deployment soon after returning from a deployment. This consecutive process, which combines the reunion phase with the pre-deployment phase, may alter spouses’ sense of stability and disrupt their routine, proving difficult for spouses to adjust to a high deployment tempo. In general, research has found military spouses to be proud and resilient; however, while spouses may feel pride and resiliency, they still may experience negative outcomes related to multiple deployments. For example, multiple deployments are associated with decreased psychological and emotional well-being, and this negative experience may be exacerbated for spouses who experience consecutive deployment cycles. 2 Alternatively, spouses may feel that with each deployment they experience, they become more familiar with the processes of preparation, separation, and reunion and over time may become habituated to the deployment cycle.
During deployments, families must also contend with a fear of what may happen to their loved ones while deployed for often lengthy and extended periods. 3 The stress experienced by miliary spouses during their deployments manifests as physical symptoms, such as headaches and unwanted loss/added weight. 4 Military spouses who experience extended deployments report significantly higher levels of loneliness, anxiety, and depression than those who do not experience such separations. 5 Research has also found higher clinical diagnoses of depression, anxiety, sleep disorders, and adjustment disorders for military wives of deployed members compared to wives of non-deployed members. 6 Although military wives do not serve directly, their health and well-being can have direct consequences for the military. Research has shown that military spouses who experience high levels of stress have a negative impact on military readiness and retention. 7
There is also some question about whether the impact of deployments may be compounded for military spouses who have children. In the 2008 ADSS, over one-third of military spouses reported having moderate to very large problems dealing with being a single parent (48 percent) and managing child care (36 percent), while over one-quarter reported similar problems finding child care when it had not been previously needed (27 percent). Thus, spouses may feel increased levels of stress during deployments both as a result of the inability to share their parenting responsibilities with the deployed parent and the difficulty meeting the additional needs of their children. 8 Despite this, studies have also found that military spouses with children experience military life as less stressful compared to those who did not have children. 9
Deployments and Social Support
Military service is characterized by a unique pattern of occupational demands, such as geographic mobility, risk of injury or death, and marital separation, which typically do not occur in the same combination or frequency for other occupations. 10 A social support network may provide stability and resources for handling the unique challenges of military life, including the impact of deployments. Social support can come from different avenues, including a spouse’s local and/or military community, friends, coworkers, and family and in a variety of ways (e.g., informational, instrumental, and emotional). 11 For example, in the 2008 ADSS, over 80 percent of respondents reported that the support they received from a network of military spouses was a helpful resource for dealing with the reunion and reintegration of their deployed husband or wife. 12
Social support may also lessen negative reactions to stressful events and foster adaptive coping behaviors. 13 A recent study of Army spouses found that deployments were the most frequent source of stress in their lives and they used coping strategies, including relying upon social support, to deal with the stress. 14 In an analysis of military wives of non-commissioned officers, perceived social support from friends was predictive of higher life satisfaction and may have acted as a buffer against feelings of fear and distress. 15 Similarly, unit support and informal community support have been found to act as buffers against deployment stress for spouses. 16 For example, informal community support (e.g., friends, organized groups, and coworkers) directly and positively affects family adaptation to deployments, indicating that social support may function as a mechanism for coping with deployment-related stress. 17 Therefore, support from within the military, as well as outside the unit, can have important effects on coping with deployments.
Purpose of Study
The main focus of this study is to explore whether multiple deployment cycles generally become more or less stressful on military spouses with each experience. While research has investigated the impact of deployments on spouses, few have had the opportunity to look at the impact of multiple deployments on stress specifically. In a 1999 study contracted by Ayn Rand Institute (ARI), outcome measures of retention, readiness, and quality of life was regressed on Personnel Tempo (PERSTEMPO), which is defined as “the number of days that Service members are away from their home station to perform their duties” (p. vii). 18 PERSTEMPO included number of deployments and length of deployment in days, but focused on the perceptions of the Service members and only on deployments across a one-year time period. Significant curvilinear trends were found between many components of these outcome measures and deployment as measured by PERSTEMPO. The trends indicated that for both length and frequency of deployments, initial and later deployment times are the most detrimental to retention, readiness, and quality of life. Moderate amounts of PERSTEMPO were either positively or insignificantly related to outcome measures. The research cautions that while nonlinear trends were apparent in the data, effects were small and may have been dependent on specific definitions of PERSTEMPO and how individual outcome measures were operationalized. However, we feel this pattern found for PERSTEMPO on retention, readiness, and quality of life, may be generalized to overall stress levels as well. Therefore, we contend that the relationship between number of deployments and stress levels is not a positive, linear progression of increasing deployments resulting in increasing stress levels. Rather, we believe the relationship between the number of deployments and stress levels in military spouses to be curvilinear in nature. Specifically, military spouses may gain a resiliency to stress after initial deployments that allows them to acclimate more readily to future deployments. Eventually, continued deployments may challenge this resiliency, leading to increased stress levels after numerous deployment cycles. Thus, a significant nonlinear relationship between number of deployments and stress is expected, such that the effect on perceived stress is a function of how many deployment cycles military spouses have experienced.
A secondary analysis will examine the role of social support in military spouses’ ability to cope with deployments. We propose that social support will account for a significant amount of the variability within spouses’ perceived stress levels, above and beyond the number of deployments experienced.
We will also examine the relationship between parental status, stress, and social support. As mentioned previously, some research indicates that spouses who are dealing with a deployment face additional burdens if they are also caring for children. However, the research on social support may suggest otherwise. 19 Parents, particularly of school age children, often have an inherent social support network through formal and informal avenues (e.g., military support services, school, and playdates), which should help in decreasing stress levels. To determine this, we will examine the relationship between parental status and stress, above and beyond number of deployments, and then look to see how social support impacts this relationship. We expect social support to compensate for the additional stress spouses with children may have. Specifically, while spouses with children may have a unique burden during deployments, we believe that the inherent social network, which often accompanies school-age children, may lessen overall stress levels. To our knowledge, no study has reviewed this potentially significant relationship.
Method
Participants and Procedure
This study used data from the 2008 ADSS, conducted by the Defense Manpower Data Center (DMDC) to assess the impact of deployments on the families of active duty members. This large-scale survey was conducted between March 14 and August 4, 2008. The target population for the 2008 ADSS consisted of spouses of active duty members of the Army, Navy, Marine Corps, Air Force, and Coast Guard, excluding National Guard and Reserve members. All spouses in the target population were married to military members who (1) had at least six months of service at the time the questionnaire was first fielded and (2) were below flag rank (e.g., general and admiral). In addition, for the respondent to remain eligible, they must have indicated at the time of the survey that they were currently married to an active duty member.
The 2008 ADSS is part of an ongoing series of military spouse research conducted by DMDC, utilizing the best methods available to reach a geographically dispersed population, including complex sampling design, both web and paper survey administration, multiple reminders, and weighting adjustments based on Department of Defense (DoD) personnel record information to account for nonresponse. 20 The web survey administration process began on March 14, 2008, with the mail-out of notification letters to sample spouses. Data were collected between March 21 and August 4, 2008.
Single-stage, nonproportional stratified random sampling procedures were used. 21 The full sample consisted of the spouses of 49,368 members drawn from the sample frame constructed from DMDC’s September 2007 Active Duty Master Edit File, September 2007 Family Database, September 2007 Active Duty Pay File, September 2007 Basic Allowance for Housing Population File, and November 2007 Defense Enrollment Eligibility Reporting System File. Spouses of the sample became ineligible if they indicated in the survey or by other contact (e.g., telephone calls to the data collection contractor) that they were divorced, widowed, or their husband or wife was no longer on active duty as of the first day of the web survey, March 21, 2008 (0.69 percent of sample). Completed surveys were received from 13,423 eligible respondents (9,016 DoD and 4,407 Coast Guard).
This specific study used three additional sample constraints. Male military spouses, spouses married to members of the Coast Guard, and spouses who reported serving in the military were not part of analyses because they are relatively rare in the population and may have unique issues. The final sample used for all analyses consisted of 6,470 female spouses of active duty military members.
The average age of female spouses of active duty military members in the sample was thirty-three. The majority of the sample was made up of non-Hispanic whites (76 percent), and all other ethnicities comprised 24 percent of the sample. Forty-three percent of the sample attended some college, and about 31 percent attained a four-year degree. Thirteen percent earned a graduate or professional degree, while the same percentage (13 percent) reported having no college education. About half of spouses were employed, and the majority (66 percent) reported feeling comfortable with their current financial condition. Most spouses were parents with 73 percent indicating they had at least one child who was eighteen years old or younger.
The primary analyses were multiple regressions using a curvilinear predictor to test if the relationship between deployments and stress levels was linear in nature or whether there was a curvilinear trend. Analyses were conducted using the software, Statistical Package for the Social Sciences.
Measures
Perceived Stress Scale
The dependent variable in this analysis is the military spouse’s current stress level. The Perceived Stress Scale is a validated short measure of stress and has been used in many studies of the impact of deployments on military members and spouses. 22 The stress scale consists of four items from the Perceived Stress Scale (see the Appendix) and demonstrates internal reliability (α = .77). Spouses were asked to rate emotional experiences/reactions in the month prior to taking the survey. The items were scored 0 to 4 (i.e., never to very often). Example items include “Felt difficulties were piling up so high that you could not overcome them” and “Felt that you were unable to control the important things in your life.” Scores are reported as the sum of the individual scores (e.g., range of 0–16), with higher scores indicating greater perceived stress. Female spouses of active duty military members in the sample reported an average perceived stress score of 5.4.
Control Variables
Spouse’s age, education level, parental and employment status, self-reported financial condition, and number of Permanent Change of Station (PCS) moves were held constant due to their influence on the relationship between number of deployments and perceived stress levels. Research has suggested that spouses may react differently to separations based on multiple variables. For example, wives aged twenty-five to thirty years report experiencing more overall worry than younger or older wives, and higher education levels are related to greater anxiety. 23 Older spouses are also more likely to have been married longer than younger spouses and may have more years of experience with being married to an active duty member than younger spouses. Additionally, often a PCS move coinciding with a deployment may, in itself, create added stress on a military spouse. 24
Predictors
Our analysis focused on two primary predictors of stress: the number of deployments female spouses of active duty military members reported experiencing and the level of social support these spouses reported having in their day-to-day lives.
Number of deployment cycles
The number of times the military member was deployed over the three years prior to survey administration was measured by spouse self-report. A deployment was defined as time away from home for military duties for thirty consecutive days or more. Number of deployments experienced in the past three years ranged from zero to more than seven (M = 1.37). Individuals who experienced more than ten deployments in the past three years were poorly represented in the sample. In order to increase the reliability and reduce skewness of the variable, values beyond ten were excluded from analysis. Within the range of one to ten deployments, the average number of deployments experienced by those in our sample was 1.38, with 33 percent experiencing no deployments in the last three years.
Social support
The Social Support measure was derived from two primary sources, RAND’s Social Support Survey Instrument from the Medical Outcomes Study and the Centers for Disease Control and Prevention’s Pregnancy Risk Assessment and Monitoring System and was adapted for military spouses by DMDC after pretesting with military spouses. 25 The Social Support Scale consisted of ten items designed to measure the degree to which spouses have a network of friends and family, other than their spouse, who provide companionship, assistance, and other types of support (see the Appendix). The scale ranged from one to five, with higher scores indicating greater perceived support. The average social support score for our sample was 3.9.
Results
Hierarchical regression was used to determine (1) whether number of deployments experienced in the past three years have a nonlinear relationship with military spouses’ perceived stress scores and (2) the impact of social support on this relationship. Following Hosek, Kavanagh, and Miller’s analysis technique, the effect of number of deployments on stress was assessed using a quadratic model. 26 The data were modeled and analyzed with polynomial regression procedures (PROC GLM) and correlation analysis. As expected, initial graphic representations of the data suggested that a cubic model (e.g., a bell shape) would be a more accurate representation of the current data than a linear model. Control variables were entered into the first step in order to partial out explained variability from these potentially confounding variables. To determine the impact of number of deployments on perceived stress, the second step included a cubic term to test the possibility that perceived stress differs across deployment cycles experienced by spouses. Finally, to explore the impact of social support on this relationship, step 3 included the variable measuring spouse reported social support. The results of the full model are shown in Table 1.
Hierarchical Regression Statistics.
Note: PCS = Permanent Change of Station; SE = standard error. R 2 = .25 (p < .001). n = 6,470.
*p < .05. **p < .01. ***p < .0001.
Table 2 displays the listwise Pearson correlations, means, and standard deviations for all variables included in the model. Control variables entered into the model at step 1 indicated a number of significant relationships (see Table 1). Specifically, there was a significant relationship between perceived stress levels and age, β = −.09, t(6463) = −6.22, p < .001, education, β = −.05, t(6463) = 3.99, p < .001, parental status, β = −.03, t(6463) = −2.29, p = .022, employment status, β = −.03, t(6463) = −2.76, p = .006, and self-reported financial condition, β = −.39, t(6463) = −33.44, p < .001. The results indicated that stress levels were higher for those female spouses of active duty military members who were younger, less educated, unemployed, and with less comfortable financial conditions. Additionally, as expected, the significant relationship between stress and parental status indicated that spouses who had children, had significantly lower stress levels. The number of PCS moves experienced by the spouse did not significantly predict stress levels.
Summary of Intercorrelations, Means, and Standard Deviations among Variables.
Note: M = mean; PCS = Permanent Change of Station; SD = standard deviation. Education level is coded as 1 = no college, 2 = some college, 3 = four-year degree, and 4 = graduate/professional degree. Employment status is coded as 1 = not employed and 2 = employed. Parental status is coded as 1 = no children and 2 = at least one child (during spouse’s most recent deployment). Perceived financial condition is coded as 1 = not comfortable, 2 = some difficulty, and 3 = comfortable. n = 6,470 (excluding missing values listwise).
*p < .05. **p < .01. ***p < .0001.
Impact of Multiple Deployments on Military Spouses
Using a cubic predictor to determine nonlinearity, a sequential regression showed a significant curvilinear relationship between number of deployment cycles experienced by female spouses of active duty military members (in the past three years) and spouses’ perceived stress, β = .23, t(6460) = 3.18, p = .001. This relationship existed above and beyond control variables of age, education level, parental and employment status, self-reported financial condition, and number of PCS moves. This relationship did not explain a significant amount of the variability previously accounted for by the control variables and reflects a unique contribution to the model.
The Role of Social Support and Parental Status
The addition of social support to the model indicated a significant relationship between social support and spouse’s perceived stress, above and beyond number of deployments and controlled variables, ΔR 2 = 0.05, β = −.23, t(6459) = −20.71, p < .001. The analyses showed a significant negative relationship with higher levels of social support predicting lower levels of stress.
As expected, while the contribution of social support did not impact the significant relationships between perceived stress and age, education, employment status, financial condition, or number of deployments, the previously significant relationship between parental status and perceived stress levels was no longer significant after partialling out the contribution of social support. Therefore, the negative relationship between parental status and stress was explained by social support. This is supported by the significant positive relationship between parental status and social support, with those wives with children reporting significantly higher levels of social support than those without children (r = .04, p < .0001).
Discussion
To our knowledge, this is the first large-scale study to examine the impact of multiple deployments on female spouses of active duty military members across all military services. Thus, the strength of this study is found in both the large sample size and, due to sampling procedures based on the parent population, the ability to generalize across all female spouses and military services. The results of this study indicate that the relationship between number of deployments and stress levels is not a simple linear one. Rather, we found a significant curvilinear relationship between number of deployments and perceived stress levels.
A significant curvilinear relationship indicates that spouses’ perceived stress levels depend on the number of deployments experienced. The specific trend in our data is illustrated in Figure 1. As is shown in this figure, as deployments initially increase, so do spouses’ perceived stress levels. After approximately two deployment cycles, we can see stress levels decreasing, potentially due to built up resiliency and acclimation to the deployment lifestyle. However, at around four to five deployments, stress levels again begin to increase, potentially reflecting the difficulty of coping with continuous and repeated deployment cycles. While we feel there is an important trend to be uncovered by these results, we recognize the lack of variability among spouse stress scores. Mean stress scores across number of deployments range between five and six. This is a relatively small change considering the Perceived Stress scale ranges from 1 to 16. However, military spouses also have a great deal of pride in their husband/wife’s military service. In fact, on a scale of one to five measuring pride in being the spouse of a military member, spouses reported an average score of 4.3. 27 Spouses who are under a great deal of stress may underreport stress levels to minimize the perceived impact of military service. Thus, despite this lack of variability, we feel that these results offer critical information in understanding how deployments may impact stress across multiple deployments.
Average stress scores of active duty military spouses by times deployed. Perceived stress ranges from 0 to 16 with higher scores indicating higher levels of stress.
While the focus on multiple deployments is quite novel, the overall curvilinear trends found in these data are not entirely new. As mentioned, previous research has found similar curvilinear trends between PERSTEMPO and retention, readiness, and quality of life. Though stress levels may initially decline as spouses learn to adapt to multiple deployments, the reasons for this are unclear. Initial deployments may result in increasing stress levels for military spouses, as they attempt to adapt; however, as a spouse becomes used to deployments and finds balance and coping strategies within this stressful situation, her overall stress level may decrease. This idea has been supported by research indicating that the first six months of deployment are more stressful than subsequent months. 28 While this research focused on length of deployment rather than number of deployments, as investigated in this study, the trend may be comparable. With concurrent deployments over a short amount of time, military spouses may deplete the reserve they developed during initial deployments, thereby accounting for the increasing stress levels after more numerous deployments. As stress is known to impact both the mental and the physical health of military spouses, multiple deployments may have long-term health implications that have yet to be measured.
Specific risk factors may also be applicable to the pattern seen in the current study. Stress from initial deployments may be a result of previously reported trends whereby young and less experienced military families are at higher risk of stress during separation. 29 Researchers in the field have also reviewed the concept of “pile up” stress, which occurs when there is an accrual of stressors over time from within the home (e.g., home maintenance and bills) and family (e.g., family illness and school obligations). 30 Such risk factors may help explain why the current study found increased stress levels initially (perhaps due to young age and less experience) and after multiple deployments (perhaps as a result of “pile-up” stress over time). Additionally, military spouses may no longer actively seek available support and resources available to them, or the resources that they relied upon during previous deployments may be exhausted (e.g., burnout in a spouse’s social support network).
A secondary analysis examined the role of social support on levels of perceived stress in female spouses of active duty military members and the role this plays for spouses with children. The sequential regression indicated that higher self-reported social support scores significantly predicted lower levels of perceived stress. The results support previous research placing emphasis on the impact of social support in mitigating overall stress levels. Therefore, policies aimed at increasing social support for military spouses should offer assistance in managing increasing stress levels related to continuous deployment cycles. With this in mind, the present study underscores the need to evaluate the well-being of military spouses along a continuum of deployments, with higher emphasis on those new to deployment and on those who have experienced a high number of deployments within a short period of time. This information has practical implications for all of the branches of the military, although there may be Service-specific nuances that are not captured by the DoD-wide analysis approach used in this study.
Moreover, the results indicated that the addition of social support to the model explained a significant amount of the variability in stress levels, previously explained by parental status. Thus, initial models indicated a significant relationship whereby female spouses of active duty military members with children had lower stress levels than spouses without children. In and of itself, this is an interesting relationship given the additional burdens that having children might place on spouses, though it is supported by research. 31 However, this relationship was rendered nonsignificant after the addition of social support to the model. Therefore, spouses with children may have lower stress levels because they also have an inherent social network of parents with whom they interact around children’s activities and school events. Alternatively, this relationship may be due to military programs aimed at providing support to military families and may represent successful outcome measures. An important implication of this finding is the potential need for specific support services geared toward spouses without children.
Implications
The results suggest that female spouses of active duty military members in the first few deployments, and spouses who have experienced high numbers of deployments, experience higher stress levels than those with more modest numbers of deployments. Service providers can use this information to target more vulnerable groups during deployments. Specifically, while spouses new to deployments may receive more support from the military, service providers may not reach out to those spouses more accustomed to deployments. The results of this study imply that the latter group of spouses may feel strained but may also be overlooked. When evaluating programs and policies aimed at maintaining well-being within military families, service providers may want to consider the continuum of adaptation represented in this study among spouses who experience multiple deployments. Military resources may need to be tailored to acknowledge that the needs of spouses during their early deployment experiences differ from later deployments. For example, while research has shown that one of the best ways to assist military families prior to separation is through support with preparedness for deployment, 32 this study suggests a need for diverse preparation strategies based on the current situation of the family. Accordingly, the preparation required of families who are dealing with an initial deployment may be drastically different than what is needed as multiple deployments occur.
In addition, this study found that a spouse’s social support network plays an integral role in decreasing her stress levels. One interesting finding is that social support compensates for the additional stress female spouses of active duty military members with children experience during deployments. In fact, once we accounted for social support, there was no significant relationship between parental status and stress levels. It is logical that the military provides support services aimed at parents who have a husband or wife deployed. The results may serve as a call for service providers to examine whether their programs address the needs of spouses who do not have children and may not be getting as much support.
Limitations
Limitations of the current study are similar to previous studies in this area. Service members may self-select into certain areas and positions which are more likely to result in multiple deployments. This selection bias is difficult to control for and should be considered in future research. 33 Additionally, while the sample of female spouses of active duty military members who experienced extreme numbers of deployments was small, their experiences could be the focus of future research. As such, qualitative work could be conducted with this group in order to assess the particular circumstances they face and their specific needs.
This study also faced several limitations due to lack of resource availability and the use of a cross-sectional design. Variables such as the duration and location of each deployment were unable to be evaluated. Survey data were only collected on the duration and location of deployments that spouses experienced in the past twelve months, rather than for the multiple deployments they experienced in the past three years. The data collection also did not identify whether the deployments military spouses experienced were combat versus noncombat deployments, which would likely impact the level of stress during the deployment. Other important factors include the amount of contact families have with the deployed member and the number and ages of the deployed member’s children.
Future Research
Researchers have investigated resiliency among military families. 34 Resiliency has generally been limited to a catchall concept that suggests an explanation as to why some families cope better with deployments than others. Little has been offered as to whether this resiliency is necessarily fixed across frequent or lengthy deployments. In other words, is resiliency a dichotomous trait (i.e., one is either resilient or not resilient), or is resiliency dynamic and dependent on families’ specific circumstances? The results of this study indicate that resiliency may be more variable across time. For example, resiliency may be strongest after experiencing a modest number of deployment cycles and weaker during an initial cycle and after experiencing several cycles. One of the strengths of this study was to provide a DoD-wide perspective on the impact of multiple deployments, and the decision to focus on the DoD as a single organization rather than a collection of organizations (e.g., the Services) was reinforced, due to issues of multicollinearity that arose when Service was added to the models. However, considering the unique demands on spouses depending on the Service of their spouse, this may be an area of future research. The data used in this study were limited by a lack of time precedence. Using cross-sectional data, we were able to uncover interesting patterns about female spouses of active duty military members; however, these patterns are limited to a “snapshot.” For example, while we measured deployments over the last three years, perceived stress was based on a measure of current personal stress. There is a critical need for future research involving longitudinal analysis of the impact of deployments on military spouse well-being. A longitudinal design would allow for utilization of more complicated analyses such as structural equation modeling to determine how the well-being of spouses is impacted over time.
Footnotes
Appendix
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.