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but all members were qualified for international military de- FIGURE 1 Mean symptom scores of the total population over the
ployment and in compliance with US Africa Command theater deployment period. Symptom scores are the sum of PHQ-9 answers
entry guidelines, which demanded a high standard of health. for questions 1–9.
A known combat casualty care event occurred on 11 February
2020. To determine if the event on 11 February was associ-
ated with significant changes to the severity of symptoms, a
Wilcoxon signed-rank test was used to compare the average
severity of symptoms before and after that date. No substan-
tial medical interventions or mental health outreach programs
were known to be provided to the volunteers. The volunteers’
duties over the course of the deployment included medical and
surgical management of patients.
The quadratic trend of length of deployment in days was also
Repeated-measures analysis using generalized mixed models significantly associated with depression severity scores, in
was applied to model whether deployment length in days was a which severity scores increased initially then decreased as days
statistically significant predictor of various outcome variables. of deployment increased (p < .001) (Figure 2). Length of de-
These variables consisted of total depression symptom score ployment was not a significant predictor on the variable pulse
(combination of depression symptoms scored together by add- (p = .416). Similarly, the length of deployment in days was not
ing scores from questions 1–9), depression severity score, pulse, a statistically significantly predictor of weight (p = .435). Last,
weight, and MAP. Mode and ranges were calculated for each the effects of length of deployment in days on arterial pressure
volunteer to provide descriptive measures for each individual. was found to be statistically significant, in which increased
All analysis was completed using SAS version 9.4 (SAS; www days of deployment was associated with lower MAP (p < .001)
.sas.com), and statistical significance was set at p = .05. (Figure 3). Spatial power covariance structures and compound
symmetry covariance structures were the specified covariance
matrices in the generalized mixed models that yielded the best
Results
fit for the various models. Depression symptoms for the pop-
The PHQ-9 questionnaire was divided into two sections. ulation followed a positive linear pattern with respect to time,
Questions 1–9 designated depression symptom scores, and and severity scores followed a quadratic trend (Figures 1 and
question 10, in which responders rate the impact of the symp- 2). To determine whether the historical event occurring on 11
toms, designated the depression severity score. In addition to February was associated with depression severity scores, the
the PHQ-9 results, pulse, weight, and MAP were tabulated pooled mean depression severity score before 11 February
(Table 1). was compared to the pooled depression severity score after
11 February 11. The Wilcoxon signed-rank test did not find
The first generalized mixed model found the deployment the difference before 11 February and after to be significantly
length in days to be a statistically significant predictor of to- different (1.15 versus 1.61, p = .125).
tal depression symptom scores. Specifically, increased days of
deployment was associated with higher depression symptom
scores (p = .015) (Figure 1). In addition, fitting a generalized Discussion
mixed model for depression severity score found the length of This study provides evidence of a linear relationship between
deployment in days to be a statistically significant predictor. duration of deployment and the frequency and severity of

TABLE 1 Aggregate Data of PHQ-9 Results and Physiologic Test Results of Deployed Participants
Volunteer (Mode, Range)
Variable 1 2 3 4 5
Question
1. Little interest in doing things 1 (0–2) 0 (0–3) 1 (0–2) 0 (0–1) *
2. Feeling down, depressed, hopeless 1 (0–2) 0 (0–3) 1 (0–3) 0 (0–2)
3. Trouble falling or staying asleep 1 (0–2) 0 (0–3) 1 (0–2) 1 (0–2)
4. Feeling tired or having little energy 1 (0–2) 1 (0–3) 1 (0–2) 1 (0–2)
5. Poor appetite or overeating 0 (0–1) 0 (0–3) 1 (0–2) 0 (0–2)
6. Feeling bad about yourself 1 (0–2) 0 (0–1) 0 (0–2) 0 (0)
7. Trouble concentrating on things 1 (0–2) 0 (0–1) 0 (0–1) 0 (0–1)
8. Moving or speaking slowly/fidgety 0 (0–2) 0 (0–1) 0 (0) 0 (0)
9. Thoughts of being better off dead 0 (0) 0 (0) 0 (0) 0 (0)
Total Symptom Score 5 (0–11) 1 (0–15) 5 (0–11) 3 (1–8)
10. Difficulty caused by symptoms 2 (1–3) 1 (1–3) 1 (1–2) 1 (1–3)
Physiologic Measurement
Pulse (beats/sec) 90 (75–106) 75 (60–95) 75 (58–104) 50 (44–97) 60 (47–74)
Mean arterial pressure (mmHg) 105 (96.5–120.5) 100 (85.5–114) 96 (77–125.5) 101 (77.5–114) 98.5 (82.5–112)
Weight (kg) 169 (167–173) 180 (92–189) 215 (201–229) — 188 (174–193)
The separate individuals are numbered with respective mode and ranges provided.

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