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. Author manuscript; available in PMC: 2024 Sep 1.
Published in final edited form as: Psychol Trauma. 2022 Apr 28;15(Suppl 2):S319–S326. doi: 10.1037/tra0001240

The Main and Interactive Effects of Distress Tolerance and Reward Function on Posttraumatic Stress Disorder Symptoms among Firefighters

Maya Zegel 1, Shelby J McGrew 1, Margaret C Wardle 2, Anka A Vujanovic 1
PMCID: PMC10191145  NIHMSID: NIHMS1895421  PMID: 35482680

Abstract

Firefighters are at heightened risk of posttraumatic stress disorder (PTSD), underscoring the importance of understanding clinically targetable factors to inform evidence-based intervention development. Hedonic capacity, or the ability to experience pleasure, is a facet of reward functioning. Anhedonia (i.e., low or absent hedonic capacity) is a hallmark symptom of PTSD. Distress tolerance (DT), or the perceived ability to withstand negative emotional states, has also demonstrated associations with PTSD.

Objective:

The purpose of the present study was to examine the main and interactive effects of self-reported hedonic capacity (Snaith-Hamilton Pleasure Scale) and DT (Distress Tolerance Scale) on PTSD symptom severity among firefighters.

Method:

A hierarchical linear regression was performed among a sample of 802 trauma-exposed career firefighters, who completed a battery of self-report questionnaires. Covariates included trauma load (i.e., number of trauma types), years in the fire service, and depression symptoms (excluding anhedonia).

Results:

Both hedonic capacity (B = 2.71, SE = 0.95, p = 0.005) and DT (B = −0.21, SE = 0.03, p < .001) were incrementally associated with PTSD symptom severity. The interactive effect of hedonic capacity and DT was associated with heightened PTSD symptom severity (B = 0.25, SE = 0.07, p < .001).

Conclusions:

Hedonic capacity and DT were independently and transactionally associated with heightened PTSD symptom severity among trauma-exposed firefighters. These findings provide evidence for the utility in developing interventions that target DT and impaired hedonic capacity among firefighters, particularly those experiencing PTSD symptomatology.

Keywords: firefighters, posttraumatic stress disorder, distress tolerance, hedonic capacity, reward

Introduction

Firefighters demonstrate high rates of trauma exposure and posttraumatic stress disorder (PTSD) compared to the general population (Meyer et al., 2012; Tomaka, Magoc, Morales-Monks, & Reyes, 2017). An estimated 91.5% of firefighters report experiencing at least one lifetime traumatic event (Meyer et al., 2012). The prevalence rate of PTSD among firefighters ranges from approximately 9% to nearly 33% (Meyer et al., 2012; Tomaka et al., 2017), which is notably higher than the estimated 4.7% past 12-month prevalence of PTSD in the general population (Kilpatrick et al., 2013). Further, subclinical or subthreshold PTSD may be particularly relevant and comparably impairing as diagnostic PTSD among firefighters who may self-select into the fire service due to greater resilience and/or who underreport PTSD symptoms due to mental health-related stigma (Chiang, Riordan, Ponder, Johnson, & Cox, 2021; Kim, Oh, Park, Min, & Kim, 2020; Korte, Allan, Gros, & Acierno, 2016). Thus, there is a need to develop specialized psychological interventions for firefighters, given the unique nature of this population.

Distress tolerance (DT), defined as the perceived capacity to withstand negative emotional states (Leyro, Zvolensky, & Bernstein, 2010), has been conceptualized as an etiological and maintenance factor relevant to PTSD with potential to inform intervention efforts (Akbari et al., 2021; Vujanovic & Zegel, 2020). Across populations, including firefighters, DT is negatively (i.e., inversely) associated with PTSD symptomatology (Fetzner, Peluso, & Asmundson, 2014; Marshall-Berenz, Vujanovic, & Zvolensky, 2011; Vujanovic, Bonn-Miller, Potter, Marshall, & Zvolensky, 2011; Zegel, Tran, & Vujanovic, 2019). Further, DT is malleable through intervention and associated with improvements in PTSD treatment outcomes (Akbari et al., 2021; Banducci, Connolly, Vujanovic, Alvarez, & Bonn-Miller, 2017; Boffa, Short, Gibby, Stentz, & Schmidt, 2018; Bornovalova, Gratz, Daughters, Hunt, & Lejuez, 2012; Vujanovic et al., in press; Vujanovic & Zegel, 2020). Understanding the interplay of DT and other psychological mechanisms with regard to PTSD among firefighters would offer a promising avenue for developing specialized interventions.

Reward functioning, a transdiagnostic mechanism connecting various psychiatric comorbidities, is a major component of behavior that guides individuals toward positive and rewarding life experiences (Nawijn et al., 2015). Hedonic capacity, or one’s ability to experience pleasure, is an aspect of consummatory reward processing (i.e., the experience of positive affect when a reward is received (e.g., Vujanovic, Wardle, Smith, & Berenz, 2017). Therefore, hedonic capacity is particularly relevant to PTSD-related negative alterations in cognitions and mood (NACM) symptoms, such as anhedonia (Nawijn et al., 2015). Low hedonic capacity may be clinically indicative of anhedonia, or a diminished ability to experience pleasure (Snaith et al., 1995), a symptom of PTSD (American Psychiatric Association, 2013). Among individuals with PTSD, low hedonic capacity is associated with more severe PTSD symptomatology, emotional numbing, and reduced connectivity in brain regions associated with reward (Pessin, Philippi, Reyna, Buggar, & Bruce, 2021). Reward functioning may be affected by PTSD symptom severity, duration, diagnostic comorbidities genetic or environmental facets, as well as cognitive-affective factors (Nawijn et al., 2015). To the best of our knowledge, no published studies to date have examined reward function among firefighters, broadly.

Further, no studies have evaluated the interplay of DT with reward functioning facets in relation to PTSD symptoms, broadly. Prior research suggests that DT and hedonic capacity are distinct constructs that independently contribute to psychopathology (e.g., Leventhal & Zvolensky, 2015). Thus, it is reasonable to expect an additive effect of these vulnerabilities, such that firefighters with lower perceived abilities to tolerate negative emotions and greater difficulties in experiencing pleasure may be at particularly heightened risk of PTSD symptoms. Low hedonic capacity tends to produce a negative cycle of disinterest in and withdrawal from positive or adaptive activities (Nawijn et al., 2015). In firefighters with low DT but normative hedonic capacity, engagement in positive activities could serve as an approach-oriented emotional coping mechanism (e.g., Nawijn et al., 2015; Vujanovic & Zegel, 2020), contributing to regulation of negative affective states. However, firefighters with both low DT and low hedonic capacity may simultaneously experience heightened distress, while also having a reduced capacity to experience enjoyment or pleasure from positive activities, thus contributing to elevated PTSD symptoms.

The purpose of this study is to examine the main and interactive effects of DT and hedonic capacity on PTSD symptom severity among firefighters. First, we hypothesized that low DT and low hedonic capacity would be independently and incrementally related to heightened PTSD symptom severity, after controlling for theoretically relevant covariates. Second, we hypothesized a significant interactive effect, such that firefighters with low DT and low hedonic capacity would report greater PTSD symptom severity. Covariates included number of years in the fire service, trauma load (i.e., number of traumatic event types), and depressive symptoms (omitting anhedonia), as consistent with past work (Akbari et al., 2021; Zegel et al., 2019). Exploratory analyses focused on evaluating PTSD symptom clusters (i.e., intrusions, avoidance, NACM, arousal and reactivity) as outcomes.

Method

Participants

The current study is a secondary analysis of data from a larger project examining stress and health-related behaviors among firefighters recruited from a large metropolitan fire department in the southern United States. All firefighters in this department provide both fire suppression and Emergency Medical Services (EMS). To be included in the current study, participants must have been a current firefighter and 18 years of age or older. Only firefighters who endorsed at least one traumatic event, as defined by the DSM-5 PTSD Criterion A (American Psychiatric Association, 2013), were included in the present analyses (N = 802). Please see Table 1 for a summary of participant characteristics.

Table 1.

Participant sociodemographic characteristics.

Mean SD Range
Age 38.7 8.5 20–63
Years in fire service 13.3 8.8 0–42
Depression symptoms 9.8 8.4 0–57
Trauma load 11.4 3.9 1–17
PTSD symptom severity 9.9 14.3 0–80
Intrusion symptom severity (Cluster B) 2.5 3.8 0–20
Avoidance symptom severity (Cluster C) 1.1 1.8 0–8
Negative alterations in cognition/mood symptoms (Cluster D) 3.0 5.0 0–28
Arousal and reactivity symptoms (Cluster E) 3.3 4.7 0–24
n Valid %
Gender
 Male 750 93.5
 Female 46 5.7
 Transgender 6 0.7
Race
 White 608 75.8
 Black or African American 99 12.3
 Other 67 8.4
 American Indian or Alaskan Native 13 1.6
 Asian 14 1.7
 Native Hawaiian or othetier Pacific Islander 1 0.1
Ethnicity
 Hispanic or Latino 212 26.4
Marital Status
 Married 548 68.3
 Single 151 18.8
 Divorced 60 7.5
 Living with partner 41 5.1
 Widowed 2 0.2
Education
 High school graduate 77 9.6
 Partial completion of college 375 46.8
 College graduate 350 43.6
Meeting criteria for:
 Probable PTSD 74 9.2
 Possibility of mild, moderate, or major depression 137 17.1
 Low hedonic capacity 193 24.1
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Note. N=802; Trauma load is defined as the number of different trauma event types experienced as reported on the LEC-5 (Weathers et al., 2013); Depression symptoms were calculated with the CES-D total, omitting the item assessing anhedonia (Radloff, 1977); PTSD total symptom severity and cluster severity scores were calculated with the PCL-5 (Blevins et al., 2015); PTSD diagnostic criteria was considered as a score of 33 or greater on the PCL-5 (Blevins et al., 2015); Participants endorsing a 15 or greater on the CES-D total were considered to have mild to severe depression symptoms (Radloff, 1977); Low hedonic capacity was determined by a score greater than 2 on the SHAPS (Snaith et al., 1995).

Measures

Demographic questionnaire.

Participants were asked to self-report demographic information and their firefighter service history. Number of years in the fire service was included as a covariate in the present analysis.

Center for Epidemiologic Studies Depression Scale (CES-D; Radloff, 1977).

The CES-D is a 20-item measure designed to assess past-week depression symptoms. Participants were asked to rate the frequency with which they experienced each symptom on a 4-point scale. A score between 15–21 is considered indicative of mild to moderate depression, while a score greater than 21 is considered indicative of possible major depression (Radloff, 1977). The CES-D is widely used in research and clinical practice and has demonstrated good psychometric properties (Orme, Reis, & Herz, 1986). In the present study, the CES-D total score was calculated while omitting the item related to anhedonia (i.e., “I enjoy life”; reverse-coded) and demonstrated good internal consistency (α=0.88). Therefore, possible CES-D total scores ranged from 0–57. The CES-D total score was included as a covariate in the current study.

Life Events Checklist for DSM-5 (LEC-5; Weathers et al., 2013).

The LEC-5 is a self-report measure used to screen for lifetime exposure to potentially traumatic life events. Participants were provided a list of 16 potentially traumatic events (e.g., combat, sexual assault, transportation accident) as well as an additional item assessing for ‘other’ potentially traumatic events not listed. Respondents are asked to indicate whether each listed event “happened to me”, “witnessed it”, “learned about it”, “part of my job”, or “not sure”. If participants endorsed that an event “happened to me”, “witnessed it”, or “part of my job”, this was considered a positive exposure to that particular type of traumatic event. Total exposures were summed to produce a trauma load variable indicating the total number of traumatic life event types experienced, and trauma load was included as a covariate in the present study.

PTSD Checklist for DSM-5 (PCL-5; Blevins, Weathers, Davis, Witte, & Domino, 2015).

The PCL-5 is a 20-item self-report questionnaire that measures past-month PTSD symptom severity, with each item corresponding to a PTSD symptom per DSM-5 criteria (American Psychiatric Association, 2013). Participants were asked to complete the PCL-5 regarding the “worst” traumatic event endorsed on the LEC-5. Participants were asked to rate each item on a 5-point scale (0 = Not at all to 4 = Extremely) to indicate how much they have been bothered by the symptom in the past month. Total symptom severity scores range from 0 to 80, with higher scores indicating greater symptom severity. A score of 33 or greater is the suggested cut-off for a probable diagnosis of PTSD (e.g., Bovin et al., 2016). The PCL-5 has demonstrated good psychometric properties (Blevins et al., 2015; Briere, 2001; Morey, 2007; Weathers, Litz, & Herman, 1993). Internal consistency was excellent for the PCL-5 total score (α=0.97), which was examined as a criterion variable in the current study. PTSD symptom clusters (i.e., intrusions, avoidance, NACM, arousal and reactivity) were examined as criterion variables in post hoc exploratory analyses and each symptom cluster demonstrated excellent internal consistency (α’s ranging from .91 to .94).

Distress Tolerance Scale (DTS; Simons & Gaher, 2005).

The DTS is a 15-item self-report measure that evaluates the extent to which participants believe they can experience and withstand distressing emotional states. Items are rated on a 5-point scale (1 = strongly agree to 5 = strongly disagree) and total scores range from 15 to 75, with higher values indicating greater levels of distress tolerance (i.e., greater perceived ability to withstand distress). The DTS demonstrates good psychometric properties (Simons & Gaher, 2005). The DTS demonstrated excellent internal consistency (α=0.93) and was included in the present study as a predictor and moderator variable.

Snaith-Hamilton Pleasure Scale (SHAPS; Snaith et al., 1995).

The SHAPS is a 14-item self-report measure designed to assess a participant’s capacity to experience pleasure, or their hedonic capacity. Responses are scored dichotomously (0 = Strongly disagree or disagree and 1 = Agree or strongly agree), with a score of 2 or greater being indicative of clinically significant anhedonia (i.e., a diminished or absent capacity to experience pleasure; Snaith et al., 1995). The SHAPS demonstrated excellent internal consistency (α=0.97). The SHAPS variable was created using the recommended scoring guidelines (i.e., categorical scoring of normal hedonic capacity as ≤ 2 and abnormal hedonic capacity > 2). The categorical variable for hedonic capacity (i.e., 0 = normative hedonic capacity and 1 = abnormal/low hedonic capacity) was evaluated as a predictor and moderator variable in the current analysis.

Procedure

Participants were recruited for the parent study via a department-wide email informing them of the opportunity to partake in an online research survey for one continuing education (CE) credit and a chance to win a raffle prize (e.g., gift card). Participation was voluntary, and firefighters could withdraw from the study at any time without penalty. The study was approved by all relevant institutional review boards.

Data Analytic Plan

All analyses were conducted using IBM SPSS Statistics version 27.0. Bivariate correlations were examined. A hierarchical linear regression was performed to examine the main and interactive effects of DT and hedonic capacity on PTSD symptom severity. Four post-hoc analyses were conducted to examine PTSD symptom clusters as outcomes and a Bonferroni correction was applied (α = 0.05/4 = 0.0125).

Results

Firefighters in the present sample reported exposure to an average of 11.39 (SD = 3.96) traumatic event types and endorsed relatively low mean levels of PTSD symptom severity (M = 9.87, SD = 14.36) on the PCL-5. Nearly one quarter of the sample (24.1%) reported abnormal (i.e., low) hedonic capacity per the SHAPS (Snaith et al., 1995). Depression symptoms (omitting anhedonia) were positively correlated with PTSD symptom severity (r = .57, p < .001) and negatively correlated with DT (r = −.17, p < .001). Trauma load was positively correlated with low hedonic capacity (r = .09, p < .05) and PTSD symptom severity (r = .10, p < .01). DT was negatively correlated with low hedonic capacity (r = −.14, p < .001) and PTSD symptom severity (r = −.29, p < .001). Low hedonic capacity and PTSD symptom severity were positively correlated (r = .12, p < .001).

Please see Table 2 for a summary of regression analyses. All analyses were also run omitting PCL-5 item 12 which assesses hedonic capacity (i.e., “Loss of interest in activities you used to enjoy”) and the pattern of findings and magnitude of effects remained consistent. With regard to PTSD symptom severity, the full model accounted for 38.3% of the variance (F(6, 795) = 82.15, p < .001). Main effects of both DT and hedonic capacity were significantly and incrementally related to PTSD symptom severity, above and beyond covariates. The interactive effect of DT by hedonic capacity was significant, as well. Simple slope analyses revealed that the interactive effect was significant only for those with normative hedonic capacity (B = −0.30, SE = 0.04, p < .001), not low hedonic capacity (B = −0.05, SE = 0.05, p = 0.369). Please see Figure 1.

Table 2.

Main and interactive effect of distress tolerance and hedonic capacity in relation to PTSD symptom severity and symptom clusters.

PTSD symptom severity B SE t P 95% CI ΔR 2 sr 2
Step 1
 Years in the fire service −0.024 0.047 −0.496 0.620 −0.117, 0.070 0.000
 Trauma load 0.128 0.106 1.201 0.230 −0.081, 0.336 0.001
 Depression symptoms 0.962 0.050 19.373 < .001 0.864, 1.059 .326 0.317
Step 2
 DT −0.206 0.032 −6.465 < .001 −0.268, −0.143 0.033
 Hedonic capacity 2.709 0.952 2.846 0.005 0.841, 4.578 .044 0.006
Step 3
 DT x Hedonic capacity 0.252 0.065 3.907 < .001 0.126, 0.379 .012 0.012
PTSD Intrusions B SE t P 95% CI ΔR 2 sr 2
Step 1
 Years in the fire service −0.005 0.013 −0.348 0.728 −0.030, 0.021 0.000
 Trauma load 0.034 0.030 1.150 0.251 −0.024, 0.092 0.001
 Depression symptoms 0.231 0.014 16.740 < .001 0.204, 0.258 .266 0.258
Step 2
 DT −0.047 0.009 −5.228 < .001 −0.065, −0.029 0.024
 Hedonic capacity 0.547 0.268 2.040 0.042 0.021, 1.074 .031 0.004
Step 3
 DT x Hedonic capacity 0.076 0.018 4.160 < .001 0.040, 0.111 .015 0.015
PTSD Avoidance B SE t P 95% CI ΔR 2 sr 2
Step 1
 Years in the fire service −0.009 0.006 −1.351 0.177 −0.021, 0.004 0.002
 Trauma load 0.032 0.014 2.229 0.026 0.004, 0.060 0.005
 Depression symptoms 0.107 0.007 15.866 < .001 0.094, 0.120 .251 0.236
Step 2
 DT −0.024 0.004 −5.449 < .001 −0.032, −0.015 0.027
 Hedonic capacity 0.165 0.131 1.258 0.209 −0.092, 0.421 .031 0.001
Step 3
 DT x Hedonic capacity 0.030 0.009 3.330 0.001 0.012, 0.047 .010 0.010
PTSD NACM B SE t P 95% CI ΔR 2 sr 2
Step 1
 Years in the fire service −0.002 0.017 −0.095 0.924 −0.035, 0.032 0.000
 Trauma load 0.028 0.038 0.734 0.463 −0.047, 0.103 0.000
 Depression symptoms 0.320 0.018 17.888 < .001 0.285, 0.355 .292 0.284
Step 2
 DT −0.076 0.011 −6.672 < .001 −0.098, −0.054 0.037
 Hedonic capacity 1.310 0.340 3.849 < .001 0.642, 1.979 .056 0.012
Step 3
 DT x Hedonic capacity 0.065 0.023 2.820 0.005 0.020, 0.111 .006 0.006
PTSD Arousal and Reactivity B SE t P 95% CI ΔR 2 sr 2
Step 1
 Years in the fire service −0.009 0.016 −0.543 0.587 −0.040, 0.023 0.000
 Trauma load 0.033 0.036 0.940 0.347 −0.036, 0.103 0.001
 Depression symptoms 0.304 0.017 18.281 < .001 0.271, 0.336 .301 0.293
Step 2
 DT −0.059 0.011 −5.488 < .001 −0.080, −0.038 0.025
 Hedonic capacity 0.687 0.322 2.134 0.033 0.055, 1.319 .032 0.004
Step 3
 DT x Hedonic capacity 0.082 0.022 3.733 < .001 0.039, 0.125 .011 0.011
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Note. N = 802. A Bonferroni correction was applied to control for Type I error rate among post-hoc analyses examining the four PTSD symptom clusters (α = 0.05/4 = 0.0125); PTSD symptom severity = PCL-5 total (Blevins et al., 2015); Depression symptoms = CES-D total, omitting the item assessing anhedonia (Radloff, 1977); Trauma load = LEC-5 total (Weathers et al., 2013); Distress tolerance (DT) = DTS total (Simons & Gaher, 2005); Hedonic capacity = SHAPS cut-off (Snaith et al., 1995), Low hedonic capacity (Yes = 1, No = 0) was determined by a score greater than 2 on the SHAPS.

Figure 1.

Figure 1.

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The interactive effect of DT and hedonic capacity on PTSD symptom severity.

Note. PTSD symptom severity was measured by the PCL-5 (Blevins et al., 2015); Hedonic capacity was assessed dichotomously with the SHAPS, with low hedonic capacity determined by a score greater than 2 and normative hedonic capacity considered as a score of 0–2 on the SHAPS (Snaith et al., 1995).

For PTSD intrusion symptoms, the full model accounted for 31.2% of the variance (F(6, 795) = 60.17, p < .001). The main effect of DT was significantly, incrementally related to PTSD intrusion symptoms; the main effect of hedonic capacity was not a significant correlate. The interactive effect of DT and hedonic capacity was significant. Simple slope analyses revealed that the interactive effect was significant only for firefighters reporting normative hedonic capacity (B = −0.07, SE = 0.01, p < .001), not low hedonic capacity (B = 0.001, SE = 0.01, p = 0.952).

Regarding PTSD avoidance symptoms, the full model accounted for 29.1% of the variance (F(6, 795) = 54.47, p < .001). The main effect of DT was significantly, incrementally related to PTSD avoidance symptoms; the main effect of hedonic capacity was not a significant correlate. The interactive effect of DT and hedonic capacity was significant. Simple slope analyses revealed that the interactive effect was significant only for firefighters reporting normative hedonic capacity (B = −0.03, SE = 0.01, p < .001), not low hedonic capacity (B = −0.01, SE = 0.01, p = 0.472).

With regard to PTSD NACM symptoms, the full model accounted for 35.4% of the variance (F(6, 795) = 72.49, p < .001). Main effects of both DT and hedonic capacity were significantly, incrementally related to PTSD NACM symptoms. The interactive effect was significant, as well. Simple slope analyses revealed that the interactive effect was significant for firefighters reporting normative hedonic capacity (B = −0.10, SE = 0.01, p < .001), not low hedonic capacity (B = −0.03, SE = 0.02, p = 0.062).

Lastly, for PTSD arousal and reactivity symptoms, the full model accounted for 34.0% of the variance (F(6, 795) = 69.68, p < .001). The main effect of DT was significantly, incrementally related to PTSD arousal and reactivity symptoms; the main effect of hedonic capacity was not a significant correlate. The interactive effect of DT and hedonic capacity was significant, as well. Simple slope analyses revealed that the interactive effect was significant only for firefighters reporting normative hedonic capacity (B = −0.09, SE = 0.01, p < .001), not low hedonic capacity (B = −0.01, SE = 0.02, p = 0.667).

Discussion

As hypothesized, significant main effects were observed for DT and hedonic capacity, respectively, with regard to overall PTSD symptom severity; main effects accounted for 4.4% of unique variance beyond covariates (Nawijn et al., 2015; Vujanovic & Zegel, 2020). While DT was negatively associated with PTSD symptom severity, low hedonic capacity was positively associated with PTSD symptomatology as consistent with past work (Akbari et al., 2021: Nawijn et al., 2015). Post-hoc analyses revealed a significant main effect of DT on the severity of all PTSD symptom clusters, such that low DT was related to heightened PTSD symptoms (and vice versa). However, hedonic capacity demonstrated a significant main effect on only the severity of PTSD NACM, such that low hedonic capacity as incrementally associated with heightened PTSD NACM symptom severity (and vice versa). Of note, all findings and magnitudes of effect remained consistent when the PTSD-related anhedonia item (i.e., “Loss of interest in activities you used to enjoy”) was removed from the PCL-5 total score. Notably, this association between low hedonic capacity and PTSD NACM is consistent with recent factor analyses of PTSD, which show that anhedonia (i.e., significantly diminished hedonic capacity) relates most robustly to the NACM cluster, including detachment and restricted affect (Armour et al., 2015).

Furthermore, significant interactive effects were documented, although the forms of the interactions were not fully consistent with hypotheses. The association between low perceived DT and heightened PTSD symptom severity was significant among firefighters with normative hedonic capacity (see Figure 1). Firefighters experiencing low hedonic capacity reported elevated PTSD symptoms, regardless of their level of perceived DT, and those with low perceived DT report greater PTSD symptoms regardless of their level of hedonic capacity. Among firefighters with higher perceived DT, those with low hedonic capacity demonstrated greater PTSD symptom severity than those reporting normative hedonic capacity. This may be consistent with the Emotional Context Insensitivity hypothesis (Bylsma, Morris, & Rottenberg, 2008; Rottenberg, Gross, & Gotlib, 2005), which demonstrates that low hedonic capacity is associated with not only diminished positive emotional reactivity but diminished negative emotional reactivity as well (Saxena, Luking, Barch, & Pagliaccio, 2017). For firefighters with heightened perceived ability to tolerate negative emotional states, blunted reactivity to reward may exacerbate PTSD symptoms; or conversely, PTSD symptoms among firefighters with heightened perceived DT may diminish hedonic capacity. Future work, incorporating experimental and multimodal indices of DT and reward functioning among firefighters, is needed to improve our understanding of these factors and their interplay with regard to PTSD symptoms.

A significant interactive effect was found for PTSD symptom severity and each of the PTSD symptom clusters, and these interactions accounted for approximately 1–2% of unique variance in PTSD symptomatology. Notably, these significant interactive effects emerged after controlling for robust, theoretically relevant covariates (R2 = .251 - .326) and main effects (ΔR2 = .031 - .056). This is consistent with extant research on DT, which consistently documents relatively small effect sizes (e.g., 2–3% unique variance) for interactions with DT among clinical samples (e.g., Ali, Seitz-Brown, & Daughters, 2015). The interactive effects of DT and normative hedonic capacity with regard to PTSD symptom cluster severity and the main effects of DT with regard to all PTSD symptom clusters suggest that it is important to clinically address DT among trauma-exposed firefighters experiencing subclinical or diagnostic PTSD symptoms. Further, the main effects of hedonic capacity on PTSD symptom severity as well as PTSD NACM symptom severity emphasizes the potential clinical utility of treatments that address anhedonia. Thus, DT enhancement skills and behavioral activation may be effective clinical directions for firefighter populations.

Study limitations should be noted. First, the study utilized a cross-sectional design and relied exclusively on self-report measures for variables of interest. Specifically, hedonic capacity was assessed categorically with the SHAPS. Although the standardized scoring guidelines were followed, the recommended categorical scoring system limits examination of the self-reported continuum of hedonic capacity, and more broadly, consummatory reward functioning. It is recommended that future work extends upon these findings by measuring hedonic capacity continuously using various methodologies (e.g., experimental indices of various facets of reward functioning). Additionally, future research in this domain would benefit from the inclusion of clinician-administered assessments of comorbid mental health diagnoses. Future work should evaluate multimodal indices of DT and reward functioning, utilize interview-based measures of PTSD symptomatology, and incorporate longitudinal and experimental methodologies to better understand temporal and causal relations among the constructs of interest. Second, although 9.2% of firefighters in this sample reported symptoms consistent with a probable PTSD diagnosis, this is generally lower than what has been reported by other firefighter samples (e.g., Tomaka et al., 2017). This may be a reflection of the stigma and underreporting associated with mental health symptoms in this population (Haugen, McCrillis, Smid, & Nijdam, 2017; Johnson et al., 2020; Jones, Agud, & McSweeney, 2020; Vujanovic & Tran, 2021). However, these findings are notable, as this is approximately double the 4.7% past 12-month prevalence of PTSD estimated in the general population (Kilpatrick et al., 2013), and there was observed variability in the reported PCL-5 scores (M = 9.9, SD = 14.3, Range = 0–80). Third, and relatedly, we recommend that factor analyses are employed to examine DT and hedonic capacity among more representative populations of firefighters (e.g., nationally representative samples) or more specific subsets of the firefighter population (e.g., treatment-seeking samples; firefighter samples with diagnostic PTSD). Finally, the sample was comprised of predominantly white, male firefighters in an urban fire department, underscoring the need to replicate this work in more racially, ethnically, and gender diverse samples. Future research should examine the role of religiosity/spirituality, race and ethnicity, and other cultural factors (e.g., racial discrimination) that may be related to the manifestation of DT, hedonic capacity, or PTSD symptomatology. This line of inquiry has potential to inform our understanding of firefighter behavioral health and to inform specialized intervention programs for this understudied and underserved population.

Clinical Impact Statement.

Results suggest that firefighters with PTSD symptoms may benefit from treatments that address an individual’s ability to tolerate distress and/or their capacity to experience pleasure.

Acknowledgements

This work was supported, in part, by a National Institute on Alcohol Abuse and Alcoholism award (NIAAA F31AA029022) to the first author. Research reported in this publication was supported, in part, by the National Institute on Minority Health and Health Disparities (NIMHD U54MD015946). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

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