Introduction

Tactical professionals, who include military, law enforcement, and firefighters1, are exposed to potentially traumatic events more often than most other professionals2. Repeated exposure to these traumatic events, including combat in military service members3, has been shown to correspond with heightened risk for mental health challenges, including greater vulnerability to post-traumatic stress symptomology (PTSS)4 and the onset of post-traumatic stress disorder (PTSD)5.

The emotional impact of trauma is marked by alterations in cognition6, such as reliving the traumatic event through intrusive memories or dissociative flashbacks and difficulties in concentration7. While such trauma symptoms have traditionally been examined in patients with PTSD diagnoses8, recent studies have adopted a broader methodological approach by examining PTSS on a continuum in individuals with varying degrees of impairment9. Findings from these investigations suggest that cognitive processes, such as attention10, problem-solving11, and working memory12 are implicated in the progression of PTSS. Given the pivotal role of cognition in trauma-related impairment, there has been growing interest in examining the relationship between PTSS and cognitive functioning. Such examinations have been conducted via laboratory tasks13 and self-reported instances of cognitive failures14, operationalized as attentional lapses, and cognitive and action slip-ups15.

Everyday cognitive failures may occur frequently but are, by and large, innocuous in daily life. Some common experiences of such failures include failing to notice signposts on the road, forgetting appointments, or daydreaming instead of listening to someone15. Such everyday cognitive failures are typically assessed using self-report questionnaires designed to capture their frequency of occurrence in daily life, thereby providing an ecologically valid measure of everyday cognitive functioning. While such failures occur in healthy individuals, greater PTSS severity is known to be associated with higher frequency of their occurrence16. Likewise, individuals diagnosed with PTSD report more frequent failures compared to healthy controls17,18.

One recent study examined the associations between trauma load, PTSS, and workplace cognitive failures in civilian tactical professionals (i.e., firefighters)19. Firefighters with higher PTSS were more likely to self-report occupationally relevant cognitive failures, such as failing to pay attention to alarms or pressing the wrong button on computers or equipment20. Trauma load21 was also associated with the severity of PTSS, and PTSS mediated the association between trauma load and cognitive failures in firefighters19. Such findings underscore the interrelated nature of trauma exposure, trauma symptomatology, and self-reported cognitive errors during real-world task performance in tactical professionals.

While several studies have examined the relationship between traumatic experiences, such as those that military service members may experience during combat, and PTSS as well as PTSD, there is a paucity of studies examining the interplay between these factors in deployable active-duty military service members. This is particularly true of active-duty elite military personnel, such as Special Operations Forces (SOF), who face an increased operational tempo relative to conventional forces, while requiring optimal cognitive functioning to maintain mission success22.

SOF personnel often navigate high-risk, clandestine military missions to terror-prone regions of the world22. They undergo a rigorous selection and training process23 and emerge as “specialist generalists” noted for their agile expertise24. They are frequently the first military service members deployed in high-risk operations25, and engage in more frequent combat operations26 compared to conventional forces23,27. Given the high-stakes environment of military operations, even minor attentional lapses could lead to consequential outcomes, such as failures to meet mission objectives, significant injury20, or, tragically, death. Despite SOF personnel experiencing more frequent exposure to combat operations, associations between combat and probable psychological disorders, such as PTSD, are weaker in magnitude in this population compared to conventional military forces22,27. While such results have been attributed to selection and training factors, combat exposure in SOF personnel may still be associated with other behavioral challenges contributing to cognitive failures.

Indeed, in elite military contexts, combat experiences have been shown to correspond with sleep disturbances and alcohol problems22,27. Despite recommendations for a minimum of seven hours of nightly sleep for optimal cognitive function28, SOF personnel often face irregular and inadequate sleep patterns due to prolonged missions exceeding 24 h. This sleep deficiency has been found to predict poor cognitive performance in laboratory-based29 and workplace settings30,31. Moreover, greater alcohol problems in trauma-exposed veterans have been associated with poorer everyday cognitive functions, such as verbal learning and working memory32. Thus, the contribution of sleep disturbances and alcohol problems may be important to consider in examining the interplay between combat exposure and cognitive failures.

Herein, we examined these interrelationships in deployable SOF personnel. In doing so, we aim to extend prior findings reported across a variety of tactical professionals and conventional military forces, to include those elite forces who are not only selected to best meet demanding circumstances but are exposed to them more frequently. Motivated by prior results19, we hypothesized that increases in combat experiences may correspond with increases in PTSS, and that increases in PTSS may correspond with increases in everyday cognitive failures. Further, we hypothesized that PTSS may mediate the association between combat experiences and everyday cognitive failures. Finally, the putative influence of sleep disturbances and alcohol problems were also considered as covariates in path analyses.

Methods

The data for this study, which were collected as part of a larger investigation on the effects of mindfulness training on cognitive resilience in elite military service members33, were collected at baseline prior to assignment to any study intervention arm. Further details regarding participant recruitment and additional study outcomes may be found in Zanesco et al.33.

Participants

Active-duty participants were recruited from two Special Operations Forces (SOF) units at a U.S. Military installation (N = 120) in the Fall of 2017. One participant subsequently withdrew from the study and was excluded from all study analyses, resulting in a total of 119 study participants. Participants included both operational and support personnel.

All service member participants provided informed consent in compliance with the Institutional Review Board of the University of Miami with oversight from the Human Research Protections Program of the Uniformed Services University of the Health Sciences. All procedures in the study were approved by the University of Miami Institutional Review Board with oversight from the Human Research Protections Program of the Uniformed Services University of the Health Sciences. All testing occurred during participants’ duty day. Per Department of Defense (DoD) regulations regarding service member compensation during the duty day, participants were not compensated beyond their wages for participation in the project.

Procedure

Participants completed a computer-based testing session comprising a series of self-report questionnaires and two cognitive tasks. Given the focus of the current paper on the putative relationships between combat experiences, the severity of PTSS, and everyday cognitive failures, a relevant subset of these measures is discussed below. Testing was proctored by a team of 1–3 experimenters in a group setting of up to 16 participants. Each session lasted approximately two hours and took place in a quiet classroom on the military installation.

Measures

Participants’ self-reported combat experiences, PTSS, and everyday cognitive failures were assessed using a series of questionnaire instruments. Secondary measures assessing sleep disturbances and alcohol problems were also included.

Combat experiences scale

Participants’ prior combat experience was measured with 17 items adapted from previous studies with soldiers34,35. Items on this questionnaire assessed how many times participants reported experiencing combat-related events (e.g., “shooting or directing fire at an enemy”) during combat deployments since September 11th, 2001. Each item was rated on a scale from 1 to 4 (1 = “never”, 2 = “1 time”, 3 = “2–4 times”, or 4 = “5 or more times”). For example, a response of 2 indicated experiencing a combat-related event one time since September 11th, 2001. Items were averaged to obtain an overall score, with higher scores indicating greater frequency of combat experiences. One participant only answered some of the questions for this questionnaire (i.e., one question was unanswered). We nevertheless included their score as the average of completed items. Cronbach’s alpha for this questionnaire indicated high internal consistency (α = 0.940).

Post-traumatic stress disorder checklist for military populations

Participants completed the Post-Traumatic Stress Disorder Checklist for military populations (PCL-M)36,37 to assess DSM-IV symptoms of PTSD relating to “stressful military experiences.” The PCL-M asks participants to indicate how often, over the past month, they have been bothered by each of the 17 possible symptoms listed. The list was tailored for the military context, and included PTSS such as intrusions, avoidance and arousal-related symptoms, and negative affective experiences (e.g., “repeating, disturbing memories, thoughts, or images of a stressful military experience”). Each item was to be rated on a scale from 1 to 5 (1 = “not at all”, 2 = “a little bit”, 3 = “moderately”, 4 = “quite a bit”, or 5 = “extremely”), with higher scores indicating greater severity of PTSS. A cutoff score of 50 or higher has been used in prior research to indicate the presence of PTSD in military settings38,39. Item responses were summed to obtain a total score ranging from 17 to 85. Cronbach’s alpha for this questionnaire indicated high internal consistency (α = 0.907).

Cognitive failures questionnaire

Participants completed the Cognitive Failures Questionnaire (CFQ)15 to assess attentional and cognitive lapses in daily life. The CFQ comprises 25 questions about “minor mistakes which everyone makes from time to time” occurring over the past month. Example questions on this measure include, “Do you find you forget appointments?” “Do you fail to notice signposts on the road?” and “Do you fail to listen to people’s names when you are meeting them?” Each item was rated on a scale from 0 to 4 (0 = “never”, 1 = “very rarely”, 2 = “occasionally”, 3 = “quite often”, and 4 = “very often”), with higher scores indicating greater frequency of cognitive failures. Responses were summed to obtain total scores ranging from 0 to 100. Cronbach’s alpha for this questionnaire indicated high internal consistency (α = 0.930).

Pittsburgh sleep quality index

Participants completed the Pittsburgh Sleep Quality Index (PSQI)40 to assess sleep quality and disturbances over a one-month interval. The PSQI comprises a series of 19 questions grouped into seven components. An example question from the PSQI states, “During the past month, how would you rate your sleep quality overall?” The scale for this question indexing sleep quality ranged from “Very Good” to “Fairly Good” to “Fairly Bad” to “Very Bad.” Notably, PSQI question scales vary based on the component probed. Scores of the seven PSQI components were summed to produce a global score ranging from 0 to 21, with higher scores indicating poorer sleep quality and a score greater than 5 indicating significant sleep disturbance40. Cronbach’s alpha for this questionnaire was calculated on the seven component scores and indicated acceptable internal consistency (α = 0.807).

The alcohol use disorders identification test-consumption

Participants were administered the Alcohol Use Disorders Identification Test Consumption (Audit-C)41 to assess hazardous drinking behaviors or active alcohol use disorders. The Audit-C is a modified version of the original, 10-item Audit measure42 and comprises 3 questions probing alcohol consumption and the frequency of such consumption (e.g., “How often do you have a drink containing alcohol?”). Each item was rated 0–4, and items were totaled deriving a score of 0–12. Scores of 4 or greater indicate the presence of hazardous drinking behaviors or an active alcohol use disorder in participants. Cronbach’s alpha for this questionnaire indicated acceptable internal consistency (α = 0.747).

Data analysis

Scores on each questionnaire were calculated in line with survey instructions. On question 1 of the PSQI (i.e., “During the past month, when have you usually gone to bed?”), two participants provided responses that were incompatible with the reported time they awoke in the morning (question 3) and reported sleep duration (question 4). Participants reported “usually going to bed” at 11:30 AM and 10:30 AM, respectively. These responses were considered inadvertent entries, and as such, responses were adjusted to reflect PM hours.

To examine associations between measures of interest (i.e., CES, PCL-M, CFQ, PSQI, AUDIT-C), a series of bivariate correlations between measures were calculated. Mediation analyses were subsequently conducted using structural equation modeling implemented in the lavaan package43 in R44 to investigate whether PTSS significantly mediated the relationship between combat experiences and everyday cognitive failures. Mediation procedures were conducted using the product-of-coefficients method45. Regression coefficients were obtained from the structural equation model to determine the effect of the independent variable (i.e., CES) on the mediating variable (i.e., PCL-M; path a), as well as the mediating variable on the dependent variable (i.e., PCL-M on CFQ; path b). A regression coefficient representing the direct effect of CES on CFQ (path c') was also obtained. The indirect (mediating) effect was obtained by calculating the product-of-coefficients (paths a*b). The path diagram representing this mediation model is depicted in Fig. 1A.

Figure 1
figure 1

Mediation models of the separate roles of PTSS, sleep disturbances, and alcohol problems on the relationship between combat experience and everyday cognitive failures. Path values are standardized regression coefficients. (A) PTSS significantly mediated the relationship between combat experience and everyday cognitive failures. (B) PTSS significantly mediated the relationship between combat experience and everyday cognitive failures, while sleep disturbances did not significantly mediate this relationship. (C) PTSS significantly mediated the relationship between combat experience and everyday cognitive failures, while alcohol problems did not significantly mediate this relationship. *p < 0.05; **p < 0.01; ***p < 0.001.

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The same analytical procedure was applied to examine two covariates, including sleep disturbances and alcohol problems, as potential mediators of the relation between combat experiences and everyday cognitive failures. These variables were included as mediators alongside PTSS (see Fig. 1B,C for visual representations of these models). Specifically, we examined two bivariate mediation models examining the separate mediating effects of sleep disturbances and alcohol problems on the association between combat experiences and everyday cognitive failures.

Results

Demographic and descriptive statistics

Data from 119 male participants were included in analyses for the self-reported measures of interest (i.e., CES, PCL-M, CFQ, PSQI, and Audit-C). On average, participants were 33 years old (SD = 5.62) and completed 11 years (SD = 5.01) of military service, with an average of 1.76 years (SD = 1.45) spent in military deployments. Nearly a quarter of participants (i.e., 23.53%) held a bachelor’s degree, while almost half (i.e., 44.54%) completed some college. Participant demographics are reported in Table 1.

Table 1 Demographics table.
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The average score on the CES was 2.09 (SD = 0.81, range = 1–4). As detailed in the "Methods" section, the CES assesses the frequency of participants’ exposure to combat-related events since September 11, 2001, with a response of 2 indicating experiencing such an event once. Thus, the mean score on this measure (i.e., 2.09) indicates that, on average, participants experienced a range of combat-related events approximately once since September 11, 2001. Scores on the PCL-M were 25.12 (SD = 9.42, range = 17–67) on average. Except for two service members, participants scored below the previously suggested clinical cut-off for the PTSS (i.e., scores > 5038,39). On the PSQI, the mean score was 5.51 (SD = 3.75, range = 0–17), consistent with scores reported in prior SOF studies27. Notably, 42% of participants (n = 50) scored within a range indicating significant sleep disturbances (i.e., scores > 540). The average score on the AUDIT-C was 3.71 (SD = 2.31, range = 0–11), which is lower than average scores reported in prior studies with SOF27. In addition, 53% (n = 63) of participants’ scores reflected hazardous drinking behavior (i.e., scores > 341). Finally, the mean score on the CFQ was 31.24 (SD = 14.38, range = 0–73). Means and standard deviations for outcomes of interest are reported in Table 2.

Table 2 Descriptive statistics and correlations between measures.
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Correlation results

Bivariate correlations investigating the correspondence between measures of interest were conducted and motivated the subsequent mediation analyses. Combat experience was positively correlated with PTSS (r = 0.336, p < 0.001), cognitive failures (r = 0.228, p = 0.012), as well as sleep disturbances (r = 0.215, p = 0.019), but not with alcohol problems (r = 0.055, p = 0.552). Similarly, PTSS was positively correlated with cognitive failures (r = 0.469, p < 0.001), sleep disturbances (r = 0.653, p < 0.001), but not with alcohol problems (r = 0.121, p = 0.188). However, cognitive failures were positively correlated with both sleep disturbances (r = 0.376, p < 0.001) and alcohol problems (r = 0.459, p < 0.001). No significant associations were observed between alcohol problems and sleep disturbances (r = 0.060, p = 0.518). Bivariate correlations between measures of interest are reported in Table 2.

Mediation results

Results from the mediation analyses suggested that greater combat experience was associated with greater symptoms of PTSD (path a, r = 0.336, p < 0.001), which were, in turn, associated with greater cognitive failures in daily life (path b, r = 0.443, p < 0.001). Mediation analyses revealed a significant indirect effect, such that PTSS mediated the relationship between combat experiences and everyday cognitive failures (path a*b, r = 0.149, p = 0.002). The total effect of combat experiences on cognitive failures was also significant (path c, r = 0.228, p = 0.010). The direct effect of combat experiences on cognitive failures in daily life was not significant in this model (path c′, r = 0.080, p = 0.352), after accounting for the indirect effect. Model covariates, including sleep disturbances and alcohol problems, did not significantly mediate the association between combat experience and everyday cognitive failures, and PTSS remained a significant mediator in the presence of these covariates (see Fig. 1B,C). Taken together, these results indicate that PTSS mediates the relation between combat experiences and everyday cognitive failures. Standardized path coefficients (expressed as r) are illustrated in Fig. 1A, and both unstandardized and standardized path coefficients are reported in Table 3.

Table 3 Path coefficients from mediation models.
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Discussion

The present study examined associations between past combat experiences, PTSS, and everyday cognitive failures in a cohort of deployable SOF personnel. Consistent with prior studies on the emotional consequences of war on conventional military forces and veteran populations46,47, we observed significant associations between combat experiences and PTSS. Also, in line with prior investigations9,14, we found that higher PTSS significantly corresponded with greater self-reported everyday cognitive failures. Furthermore, consistent with findings from Jozani et al.19 suggesting that PTSS severity mediated the correspondence between traumatic exposure and cognitive failures, our results indicated that the severity of PTSS may explain the association between combat experiences and everyday cognitive failures in SOF personnel.

These results suggest that among deployable elite military service members who are not only selected for but also exposed to dangerous and high-risk military missions23, there are significant interrelationships between combat exposure, PTSS, and everyday cognitive failures. Notably, the vast majority of SOF personnel in the present study reported low levels of PTSS. Yet, we still observed significant associations between PTSS severity and the frequency of everyday cognitive failures. Given the potential operational costs of cognitive failures during missions, these findings motivate the need for further exploration of the intersections between combat exposure, trauma symptoms, and attentional lapses in real-world scenarios, as well as the continued implementation of protective strategies and solutions48.

Indeed, the majority of prior studies examining the costs of traumatic experiences have focused on individuals with PTSD diagnoses29. To build upon these clinically meaningful findings, the present study suggests that when examining a continuum of post-traumatic stress symptom severity, subclinical levels similarly correspond with combat exposure and everyday cognitive failures. This approach was warranted, as participants endorsed a wide range of PTSS. Future investigations should consider examining PTSS along a continuum to ensure that the breadth of such symptoms may be captured even in non-clinical active-duty service members.

The present study also investigated self-reported sleep disturbances and alcohol problems as covariates. In two separate models, which tested the indirect effects of PTSS alongside sleep disturbances, and of PTSS alongside alcohol problems, only the indirect effect of PTSS remained significant in the presence of study covariates. Such results suggest that PTSS largely accounts for the effects of combat experiences on everyday cognitive failures. Future longitudinal studies with larger sample sizes may examine the precise temporal dynamic interplay between all factors examined herein.

While many aspects of our results extend and replicate prior findings in conventional forces, veterans, and civilian tactical professionals, the present study is limited in several ways. First, the present investigation is limited by a cross-sectional study design, and therefore, results should be interpreted with caution. Our findings suggesting that PTSS may explain the correspondence between combat experiences and everyday cognitive failures are preliminary, and temporal relationships between outcomes cannot be inferred. To confirm causal connections in such mediational relationships, longitudinal investigations are necessary.

Second, we were unable to access service members' medical records or conduct formal interview-based clinical assessments of PTSD and other psychological or neurological disorders, such as traumatic brain injury (TBI). To index trauma symptomology and neurological history more robustly, future investigations may consider conducting clinician-administered interviews in addition to collecting self-report data, as was done for PTSS herein. TBIs are common among combat-exposed military personnel, as reported in prior research49,50. Studies have shown that a history of TBIs correlates with both PTSS51 and everyday cognitive failures52. Therefore, future research examining the relationship between PTSS and everyday cognitive failures may consider including more thorough clinical assessments of participants.

More thorough assessments would also allow for a fine-grained, symptom-specific understanding of the relationships between symptoms and everyday cognitive failures. For example, investigating whether hypervigilance (more so than other symptoms) corresponds with everyday cognitive failures would provide a more nuanced understanding of symptom-specific vulnerabilities in tactical professionals.

Nevertheless, these findings underscore the significant link between trauma symptoms and real-world cognitive failures in an understudied elite military population. Given the high-stakes costs of mission failure for SOF and other tactical professionals who will experience trauma as part of their professional lives, these results highlight the need for ongoing research to characterize their vulnerabilities and motivate the continued implementation of therapeutic and readiness solutions to protect against such outcomes.