Journal of Pediatric Psychology Advance Access published March 29, 2015

Journal of Pediatric Psychology, 2015, 1–8 doi: 10.1093/jpepsy/jsv026 Original Research Article

Acute Pain and Posttraumatic Stress After Pediatric Injury

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Department of Psychology, Drexel University, 2The Center for Injury Research and Prevention, The Children’s Hospital of Philadelphia, 3Department of Psychiatry, University of Pennsylvania, and 4Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania All correspondence concerning this article should be addressed to Aimee K. Hildenbrand, MS, Department of Psychology, Drexel University and The Center for Injury Research and Prevention, The Children’s Hospital of Philadelphia, 3535 Market Street, Suite 1150, Philadelphia, PA 19104, USA. E-mail: [email protected] Received November 25, 2014; revisions received February 21, 2015; accepted February 25, 2015

Abstract Objective Using a prospective, longitudinal design, we examined the relationship between acute pain and posttraumatic stress symptoms (PTSS) in youth following injury. Methods Children aged 8–17 years who sustained an injury (N ¼ 243) and their parents participated in baseline interviews to assess children’s worst pain since injury. 6 months later, participants completed follow-up interviews to assess child PTSS. Results Pain as assessed by the Color Analogue Pain Scale (CAS) predicted PTSS 6 months after injury, even when controlling for demographic and empirically based risk factors. On the other hand, pain as assessed by the Faces Pain Rating Scale was not a significant independent predictor of PTSS. Conclusions The CAS may be a useful addition to existing screening tools for PTSS among children. Additional research is warranted to understand underlying mechanisms linking acute pain and PTSS to improve assessment, prevention, and treatment approaches and promote optimal recovery after pediatric injury. Key words: injury; pain; posttraumatic stress; PTSD.

Unintentional injury is an extremely common experience and a leading cause of disability for children across the globe (Peden, 2008). Each year, 20 million children in the United States alone suffer injuries, with nearly nine million of these children requiring emergency medical care (Borse et al., 2009). Given the high prevalence of pediatric injury both domestically and globally, understanding children’s recovery after injury has clear public health significance. In particular, identifying potential risk factors for poor psychosocial outcomes after injury (e.g., posttraumatic stress, new fears, mood changes, poor academic performance) could inform screening and secondary prevention approaches, thereby facilitating healthy recovery for children with injuries. While most children who sustain injuries recover physically, a significant subset experience negative psychological consequences that impair functioning (Basson et al., 1991; DeVries et al., 1999; Di Gallo, Barton, & Parry-Jones, 1997). In particular, a considerable proportion of injured children and their parents report

persistent posttraumatic stress symptoms (PTSS; Daviss et al., 2000; DeVries et al., 1999; Holbrook et al., 2005; Stoddard & Saxe, 2001; Winston et al., 2003). PTSS include reexperiencing or intrusion, avoidance of trauma reminders, hyperarousal, dissociation, and a myriad of negative moods or cognitions (American Psychiatric Association, 2013). PTSS are strong predictors of impaired functioning and health-related quality of life, interfere with adherence to medical recommendations, and are linked to poorer health outcomes and greater use of health-care services (Graham-Bermann & Seng, 2005; Holbrook et al., 2005; Landolt, Buehlmann, Maag, & Schiestl, 2009; Landolt, Vollrath, Gnehm, & Sennhauser, 2009; Seng, Graham-Bermann, Clark, McCarthy, & Ronis, 2005; Thorp & Stein, 2005; Vanderbilt et al., 2008; Zatzick et al., 2008). Clearly, PTSS pose a major threat to children’s physical and emotional health and recovery after injury. Given the negative impact of PTSS on children’s recovery following injury, a growing body of research has examined potential risk

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Aimee K. Hildenbrand,1,2 MS, Meghan L. Marsac,2,3 PHD, Brian P. Daly,1 PHD, Douglas Chute,1 PHD, and Nancy Kassam-Adams,2,4 PHD

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such as physical injury. Additionally, acute dosage of opiates has been linked to reduced PTSS in several small naturalistic studies (Nixon et al., 2010; Saxe et al., 2001, 2006; Stoddard et al., 2009). These findings suggest that morphine attenuates adrenergic activation associated with enhanced memory consolidation, thereby reducing risk of PTSS. These results are consistent with animal research, which has demonstrated that morphine attenuates fearconditioning processes (Good & Westbrook, 1995; McNally & Westbrook, 2003). On the other hand, it is also possible that PTSS influence pain. Sharp and Harvey’s (2001) mutual maintenance model theorizes that pain and PTSD exacerbate and perpetuate one another simultaneously, thereby creating a self-sustaining pattern of comorbidity. More specifically, this model suggests that both disorders involve anxiety sensitivity and the tendency to perceive events as catastrophic, attentional biases that increase hypervigilance toward perceived threats, and avoidance, factors that maintain each disorder simultaneously. A recent investigation by Brown, Kenardy, and Dow (2014) with children with traumatic brain injury (TBI) provided compelling empirical support for this model. However, when the conceptual models nested within the mutual maintenance model (i.e., pain predicting PTSS and vice versa) were examined separately, data suggested that only PTSS facilitated the maintenance of pain (Brown et al., 2014). Clearly, the interactions between pain and PTSS are complex and warrant additional investigation. While prior research has clearly advanced our understanding of emotional recovery after pediatric injury, little is known regarding the relationship between acute pain and PTSS after pediatric injury. The vast majority of extant research in this area has been conducted with adults and small pediatric samples primarily composed of burn patients. Furthermore, prior studies have predominantly focused on the co-occurrence of PTSS and chronic pain, rather than how acute pain may increase risk for the development of posttraumatic stress. The current study aimed to examine this relationship in a large, prospective longitudinal study of children following injury. We hypothesized that acute pain would predict PTSS 6 months later when controlling for demographic and empirically based risk factors for PTSS.

Methods Procedures This study used data collected as part of a prospective, longitudinal study designed to identify risk factors for PTSD following pediatric injury (Kassam-Adams & Winston, 2004). Parents of eligible children enrolled in the Trauma Service at a large pediatric hospital were informed of the study and invited to participate by a research assistant, trauma fellow, or trauma research nurse. After providing consent and assent, children and parents participated in baseline interviews that included assessment of children’s worst pain since the injury, perceived life threat during the injury, prior trauma history, and Acute Stress Disorder (ASD) symptoms. Baseline assessments were conducted in either the child’s hospital room or home within 4 weeks of injury (M ¼ 11.5 days, SD ¼ 10.63). Approximately 6 months postinjury (M ¼ 205.31 days, SD ¼ 73.54), children and parents participated in follow-up interviews conducted in children’s homes to assess child PTSS. This study was approved by the hospital’s institutional review board.

Participants Participants included 243 children aged 8–17 years (M ¼ 11.36, SD ¼ 2.49) who had sustained an injury requiring medical treatment

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factors to better target screening and preventive efforts. This research suggests that various biological (e.g., high heart rate or cortisol levels), psychological (e.g., prior trauma, premorbid behavioral problems, acute stress, maladaptive cognitive appraisals), and social-environmental factors (e.g., parent PTSS, poor family functioning, limited social support) may place children at risk for developing PTSS postinjury (Alisic, Jongmans, van Wesel, & Kleber, 2011; Cox, Kenardy, & Hendrikz, 2008; Kahana, Feeny, Youngstrom, & Drotar, 2006; Kazak et al., 2006; Trickey, Siddaway, Meiser-Stedman, Serpell, & Field, 2012). However, most investigations have focused on processes during the posttrauma period (Marsac, Kassam-Adams, Delahanty, Widaman, & Barakat, 2014). Furthermore, a number of barriers interfere with effective screening of children at risk for psychological sequelae during acute trauma care (e.g., time and training limitations for health-care professionals, differentiating normative distress from indicators of risk), and seemingly intuitive indicators such as injury severity have not been shown to be useful predictors of psychological outcomes (Daviss et al., 2000; DeVries et al., 1999). As a result, clinicians’ perceptions of risk for psychological sequelae are often inaccurate (Baxt, Kassam-Adams, Kazak, Balluffi, & Helfaer, 2005; Ziegler et al., 2005). Hence, there is a need to systematically identify indicators of PTSS risk in the peri-trauma period that can be easily integrated into medical care. Acute pain represents a promising avenue for identifying children who may be at risk for developing PTSS, as pain is widely assessed as part of routine medical care. Although both pain and PTSS are common after pediatric injury, their interactions are poorly understood (Gold, Kant, & Kim, 2008; Langeland & Olff, 2008). Pain has traditionally been viewed as an outcome of physical injury, yet preliminary evidence suggests that pain may also be an etiological factor for the development of PTSS (Gold et al., 2008). For example, Saxe and colleagues (2005) found that for acutely burned children, pain during hospitalization indirectly influenced later PTSS through a pathway mediated by separation anxiety. Investigations of adults following whiplash, traffic-related, and burn injuries have likewise found that pain is associated with acute PTSS and the incidence of diagnosable posttraumatic stress disorder (PTSD; Drottning, Staff, Levin, & Malt, 1995; Kuch, Cox, & Evans, 1996; Patterson, Tininenko, & Ptacek, 2006). Several theories highlight potential mechanisms by which pain can serve as a risk factor for PTSS among children. Based in neurobiological advances, fear conditioning models suggest that pain may contribute to the development of PTSS by stimulating the release of hormones that enhance fear conditioning and overconsolidation of trauma memories (Amstadter, Nugent, & Koenen, 2009; Pitman, 1989). These rapidly acquired learned associations subsequently manifest themselves as intrusive recollections and conditioned emotional responses that are extremely difficult to extinguish, the hallmark symptoms of PTSD (Pitman, 1989; Yehuda, McFarlane, & Shalev, 1998). The neurobiologic processes underlying this fear-conditioning model have been well described across both animal models and human research (Amstadter et al., 2009). Because pain and PTSD have shared neurobiological pathways (Asmundson, Coons, Taylor, & Katz, 2002; McLean, Clauw, Abelson, & Liberzon, 2005; Norman, Stein, Dimsdale, & Hoyt, 2008), it has been suggested that acute pain during or after an injury can enhance hypothalamic-pituitary-adrenal (HPA) and noradrenergic activation and thereby increase risk of overconsolidated trauma memories and PTSS. This model is supported by research indicating that memories of painful events are readily retrievable (Morley, 1993), indicating that strong encoding occurs during painful events

Hildenbrand, Marsac, Daly, Chute, and Kassam-Adams

Acute Pain and Posttraumatic Stress After Pediatric Injury Table I. Participant Demographics Children

182 (75) 61 (25) 96 (40) 135 (56) 4 (2) 8 (3) 39 (16) 81 (33) 123 (51) M (SD)

Age (years) Length of hospital stay (days) Injury Severity Score Caregivers Relationship to child Mother Father Other caregiver

11.36 (2.49) 3.25 (4.0) 7.87 (6.21) N (%) 164 (79) 25 (12) 19 (9)

Note. Participant demographics as reported at baseline enrollment.

and one parent per child. Eligibility criteria included incurring a traffic-related physical injury within the past 4 weeks, receiving medical care in the hospital, child between 8 and 17 years of age, and adequate proficiency in the English language to complete questionnaires. Children were excluded from participating in the study if their current medical status or cognitive functioning precluded completion of assessments, or if no parent was available to consent and participate in the study. Most children (75%) were male and identified as Black (56%) or White (40%). Children in this sample sustained traffic-related injuries as pedestrians (33%), bicyclists struck by a vehicle (23%), bicyclists who fell (28%), or motor vehicle occupants (16%). Approximately 42% of children suffered at least one extremity fracture. All children in this sample were admitted to the hospital for at least 24 hr, and 26% were admitted to the intensive care unit. Most participating parents (79%) were mothers. Six-month follow-up assessments were completed by 171 children (70% of participants enrolled at baseline). There were no significant differences with regard to sex, age, ethnicity, or worst pain ratings for participants that completed follow-up assessments versus those that only completed the baseline assessment. See Table I for full participant demographics. Refer to Kassam-Adams and Winston (2004) for additional details regarding participant recruitment and attrition.

Measures Pain. The Color Analogue Pain Scale (CAS; McGrath et al., 1996) is a self-report assessment of pain intensity that uses a visual analogue instrument. The CAS is composed of a 10-cm line with increasingly intense red coloring to indicate pain severity. Children slide a marker over the line to indicate their level of pain. The reverse side of this instrument indicates corresponding numeric values (0–10, rounded to the nearest 1/8 unit) for children’s pain ratings. The CAS has been used to assess pain among a wide variety of pediatric

populations that endorse pain (Bulloch & Tenenbein, 2002). Scores on this measure are strongly correlated with those from visual analogue instruments, and research suggests that the CAS is easier to administer than other visual analogue scales (McGrath & Brigham, 1992). The Faces Pain Rating Scale (FPRS; Bieri, Reeve, Champion, Addicoat, & Ziegler, 1990) is a self-report measure of pain intensity in which children choose a face that corresponds to their level of pain. The seven faces range from scores of 0 (no pain) to 6 (severe pain). This instrument has been used in many clinical settings (Bulloch & Tenenbein, 2002). While scores on the FPRS are correlated with those on traditional visual analogue scales (de Tovar, Wood, & Alibeu, 2002a; Hicks, von Baeyer, Spafford, van Korlaar, & Goodenough, 2001), some studies suggest that pediatric patients prefer the FPRS to visual analogue scales (de Tovar, Wood, & Alibeu, 2002b). The FPRS is considered an ideal instrument for assessing pain severity in children across ages, gender, and cultural backgrounds (Belville & Seupaul, 2005). The scale is thought to be superior in design to other faces scales because it does not confound pain intensity with affect (i.e., smiling and crying anchor faces; Belville & Seupaul, 2005). Both the CAS and FPRS have demonstrated good construct, content, and convergent validity and reliability in measuring acute pain in children (Bulloch & Tenenbein, 2002). In this study, children were asked at baseline interviews to use the CAS and the FPRS to retrospectively report the worst or most severe level of pain they experienced since their injury. The CAS and FPRS were administered in counterbalanced order. Perceived Life Threat. One item was used to assess children’s perceived life threat: “When you got hurt, or right afterwards, did you think you might die?” (Yes/No). Prior Trauma History. The Traumatic Events Screening Inventory for Children (Ribbe, 1996) is a 15-item, clinician-administered interview assessing children’s exposure to a variety of potentially traumatic events (e.g., prior injuries, hospitalizations, domestic violence, community violence, disasters, abuse). ASD Symptoms. The Child Acute Stress Questionnaire (CASQ; Winston et al., 2002) is a 48-item, interviewer-administered questionnaire that assesses ASD symptoms. The measure is based closely on a student version of the Stanford Acute Stress Reaction Questionnaire (Cardena, Koopman, Classen, Waelde, & Spiegel, 2000; Seagraves, Classen, Koopman, & Spiegel, 1994). Each item of the CASQ is rated on a 3-point Likert-type scale and corresponds to one of the four ASD symptom categories. Initial psychometric data for the CASQ indicate excellent internal consistency, test–retest reliability, and factor analytical support for construct validity (Winston et al., 2002). In this sample, internal consistency for the CASQ was excellent (a ¼ .92). Heart Rate. Triage heart rate was assessed as part of clinical care within 5 min of the child’s arrival to the emergency department, using cardiac auscultation, radial pulse palpation, or an automated vital-signs monitoring device (see Kassam-Adams, Garcia-Espana, Fein, & Winston, 2005 for further details). Raw heart rate values were used in analyses. Child PTSS. The Clinician-Administered PTSD Scale for Children and Adolescents (CAPS-CA; Nader et al., 2004) is a semistructured

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Gender Male Female Racial/ethnic background White Black Hispanic Other Traffic-related injury mechanisms Occupants Pedestrians Bicyclists

N (%)

3

4

Hildenbrand, Marsac, Daly, Chute, and Kassam-Adams

Table II. Correlations Among Primary Study Variables Study variables 1 2 3 4 5 6 7 8 9 10

Pain (CAS) Pain (FPRS) Age Sex Ethnicity HR at Triage Prior trauma history Acute stress symptoms Perceived life threat PTSS (CAPS-CA)

1

2

3

4

5

6

7

8

9

.76*** .05 .05 .13 .01 .01 .20** .26** .30***

.04 .05 .20** .01 .06 .14* .28*** .26**

.00 .08 .20** .01 .14* .02 .08

.00 .19** .07 .07 .15* .14

.09 .06 .07 .10 .09

.03 .14* .07 .13

.08 .03 .01

.21** .53***

.24**

10

interview that assesses PTSD symptoms and associated features. The CAPS-CA assesses the frequency and intensity of 17 symptoms corresponding to DSM-IV criteria for PTSD. The CAPS-CA also evaluates the impact of these symptoms on social, occupational, and developmental functioning, subjective distress, and global severity of PTSD. The measure has good internal consistency for each subscale (as ranging from .75 to .81), and reasonable concurrent validity with self-report measures of PTSD (Newman, McMackin, Morrissey, & Erwin, 1997). Internal consistency in the current sample was excellent (a ¼ .90). In this study, the CAPS-CA was administered at the 6-month follow-up assessment by interviewers blinded to children’s baseline ASD symptoms.

Data Analysis All analyses were conducted using SPSS statistical software, version 22. To evaluate whether pain predicted child PTSS when controlling for demographics (i.e., age, sex, ethnicity) and empirically based risk factors (i.e., HR, prior trauma, ASD symptoms, perceived life threat), we used two hierarchical regression analyses. For each regression, in Step 1, covariates (i.e., demographic and empirical risk factors) were entered. In Step 2, the main effects of acute pain were entered (i.e., worst pain rating on the CAS or FPRS). Given that scores on the CAPS-CA were highly positively skewed, a square root transformation was used to better approximate a normal curve, in accordance with recommendations by Tabachnick and Fidell (2007) and Howell (2007). Linear regression models assume normally distributed dependent variables, and a square root transformation was more successful in addressing positively skewed CAPS-CA scores than a logarithmic transformation. While distributions of pain scores for both the CAS and FPRS were negatively skewed, linear regression models do not make assumptions about the normality of predictor variables. Additionally, results were nearly identical when using the original and transformed (i.e., square root, logarithmic) CAS and FPRS variables. As such, results from regression models using the original CAS and FPRS variables are presented below.

Results Among this sample of children who sustained traffic-related injuries, worst pain by child report on the CAS ranged from 0 to –10 (N ¼ 238, M ¼ 7.80, SD ¼ 2.50). On the FPRS, worst pain by child report ranged from 0 to 6 (N ¼ 239, M ¼ 5.06, SD ¼ 1.32). Total

CAPS-CA scores ranged widely from 0 to 122 (N ¼ 177, M ¼ 27.33, SD ¼ 21.38). See Table II for a summary of relationships between primary study variables. Hierarchical regression analyses revealed that worst pain rating on the CAS was significantly associated with subsequent PTSS when holding demographic (i.e., age, sex, ethnicity) and evidence-based risk factors (i.e., HR, trauma history, ASD symptoms, perceived life threat) constant, such that higher pain predicted greater PTSS at the 6-month follow-up (R2D ¼ .032, F(1, 107) ¼ 5.674, p ¼ .019). This model accounted for approximately 35% of the variance in child PTSS. However, worst pain as assessed by the FPRS did not significantly predict PTSS when controlling for other risk factors (R2D ¼ .010, F(1, 107) ¼ 1.658, p ¼ .201). In both models (i.e., using the CAS vs. FPRS), age and ASD symptoms also emerged as significant independent predictors of subsequent PTSS in each step of the analyses. Hierarchical regression results are presented in more detail in Table III. For each of the regression analyses, all statistical assumptions were met.

Discussion Findings from this investigation extend the literature on potential risk factors for pediatric medical traumatic stress by exploring the relationship between pain and PTSS after injury. Results indicate that the most severe pain children experience during hospitalization for pediatric injury, measured retrospectively by the CAS administered within 4 weeks of injury, predicts subsequent PTSS, even after controlling for demographic and empirically based risk factors. Notably, this model accounted for more than one-third of the variance in PTSS. On the other hand, worst pain as assessed by the FPRS did not emerge as a significant independent predictor of child PTSS. Although these pain assessments operate similarly, greater variance in ratings on the CAS (i.e., 0–10, rounded to the nearest 1/8 unit) likely afforded this model increased statistical power relative to the model using the FPRS (range ¼ 0–6). Overall, findings highlight the importance of obtaining a nuanced assessment of acute pain and suggest a role for these assessments in PTSS screening protocols. The pattern of results from this study is generally consistent with prior research examining the relationship between pain and PTSS among children. Saxe and colleagues (2005) similarly found that pain as assessed by the CAS predicted subsequent PTSS among children with burn injuries. Another small study of children with injuries likewise suggested a relationship between pain (as assessed by

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Note. A square root transformation was used for the observed child PTSS variable (CAPS-CA). *p < .05. **p < .01. ***p < .001.

Acute Pain and Posttraumatic Stress After Pediatric Injury

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Table III. Predictors of Child PTSS Hierarchical regression models

b

SEb

b

.178* .568 .002 .005 .169 .096*** .439

.078 .180 .444 .104 .001 .104 .010 .041 .543 .024 .015 .503 .398 .091

Step 2 Age Sex Ethnicity Triage HR Prior trauma history ASD symptoms Perceived life threat Worst pain (CAS)

.152* .504 .002 .005 .119 .086*** .266 .180*

.077 .154 .436 .092 .001 .127 .009 .045 .532 .017 .016 .452 .396 .055 .076 .196

Model 2 Step 1 Age Sex Ethnicity Triage HR Prior trauma history ASD symptoms Perceived life threat

.178* .568 .002 .005 .169 .096*** .439

.078 .180 .444 .104 .001 .104 .010 .041 .543 .024 .015 .503 .398 .091

Step 2 Age Sex Ethnicity Triage HR Prior trauma history ASD symptoms Perceived life threat Worst pain (FPRS)

.170* .535 .002 .006 .154 .093*** .313 .192

.078 .172 .444 .098 .001 .116 .010 .046 .541 .022 .015 .487 .408 .065 .149 .106

R D

FD

R

2

R2adj

.359 8.637*** .36 .32

.032 5.674*

.39 .35

.361 8.897*** .36 .32

.010 1.658

.37 .32

Note. A square root transformation for the observed child PTSS variable (CAPS-CA) was used in these analyses. *p < .05. ***p < .001.

the FPRS) and later PTSS using bivariate correlations, yet the FPRS did not emerge as a significant predictor of PTSS in the final model that included risk factors such as fear at time of trauma, morphine use, and posttraumatic appraisals (Nixon et al., 2010). Future research should attempt to replicate these findings with these and other pain assessment instruments to further explore and clarify the relationship between acute pain and PTSS after pediatric injury. Several mechanisms may account for the relationship between acute pain after injury and subsequent PTSS among children. Recent neurobiological advances have provided compelling evidence for fear conditioning models of posttraumatic stress (Amstadter et al., 2009). In support of these models, several small studies have proposed that morphine may attenuate fear conditioning processes in children with burns and other injuries, thereby reducing the risk for PTSS (Nixon et al., 2010; Saxe et al., 2001, 2006; Stoddard et al., 2009). However, given the paucity of research in this area, additional investigations are needed to more thoroughly examine the role of fear conditioning processes and the efficacy of morphine or other opiate medications as a secondary prevention approach after pediatric injury.

The mutual maintenance model of PTSD and pain (Sharp & Harvey, 2001) has likewise garnered promising empirical support. Brown and colleagues (2014) demonstrated support for this model in a sample of children with TBI. In contrast to the current study, however, Brown and colleagues (2014) found that pain did not contribute to PTSD at any time point, although it approached statistical significance. It is possible that our findings differ from those of Brown and colleagues owing to varying sample characteristics and assessment methods. In particular, Brown et al. (2014) examined children with mild to severe TBI, a population that may experience pain differently given changes in cognitive, affective, and neurological functioning. This may limit the applicability of their findings to children with other types of injuries. Additionally, Brown et al. (2014) relied on parental assessment of children’s pain, whereas this study examined children’s self-reported pain. Prior research suggests that parents’ own trauma reactions influence their assessment of child symptoms (Kassam-Adams, Garcia-Espana, Miller, & Winston, 2006). Furthermore, pain is an inherently subjective experience that encompasses sensory, emotional, cognitive, and behavioral components that parents may not be able to directly observe. Thus, it is important to obtain children’s self-reported pain whenever possible (von Baeyer, 2009). Finally, it is also possible that a third variable such as pain catastrophizing increases the risk for both heightened pain and PTSS (Leung, 2012; Sullivan, 2012; Sullivan et al., 2001). This cognitive bias toward aversive, painful sensations and negative interpretations of pain enhances emotional distress, anxiety, and physiological arousal (Sullivan et al., 2001), which may increase susceptibility to intense pain as well as PTSS. Among adults with whiplash and musculo-skeletal injuries, pain catastrophizing is predictive of heightened pain intensity, functional disability, and PTSS (Buitenhuis, de Jong, Jaspers, & Groothoff, 2008; Carroll, Cassidy, & Cote, 2006; Carty, O’Donnell, Evans, Kazantzis, & Creamer, 2011; Sullivan, Stanish, Sullivan, & Tripp, 2002; Sullivan et al., 2009; Vangronsveld, Peters, Goossens, & Vlaeyen, 2008). Catastrophic interpretations of pain and other aversive sensations appear to develop early in life and remain relatively stable across painful experiences (Sullivan et al., 2001). Moreover, the relationship between pain catastrophizing and pain intensity has shown notable consistency across clinical populations (Sullivan et al., 2001). Thus, it may be that children prone to catastrophizing endorse more significant pain and PTSS following an injury. Although research suggests that parent behavior and catastrophizing can influence children’s pain experiences and adjustment (Chambers, 2003; Chambers, Craig, & Bennett, 2002; Chambers, Taddio, Uman, & McMurtry, 2009; Wilson, Moss, Palermo, & Fales, 2014), less is known regarding the role of children’s own pain catastrophizing in the development of PTSS postinjury, and this study did not assess this construct. Further research is needed to carefully examine biopsychosocial mechanisms underlying the association between pain and PTSS among children who have sustained injuries.

Limitations and Future Directions Several limitations of the current study should be noted. Most notably, this investigation used secondary data analysis, and the larger study from which these data were obtained was not designed specifically to examine the relationship between pain and PTSS. Moreover, we did not examine, control for, or manipulate opiate medications or family and medical providers’ responses to children’s pain, which can influence child perception of pain intensity and pain-related distress (Wilson et al., 2014). Future research should seek to use experimental designs to enable greater control over potential confounding

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Model 1 Step 1 Age Sex Ethnicity Triage HR Prior trauma history ASD symptoms Perceived life threat

2

6

Clinical Implications Results from this investigation have several implications for clinical practice and the refinement of screening tools for traumatic stress following pediatric injury. Findings from this study suggest that retrospective recall of more severe pain during the peri-trauma period, as assessed by the CAS, is associated with greater risk for persistent PTSS, even when controlling for empirical risk factors. Given that pain is regularly assessed by various clinicians during routine medical care, the CAS and similar measures providing nuanced assessments of pain may thereby represent feasible additions to PTSS screening tools. The CAS requires minimal training, is simple and quick to administer, has demonstrated validity across a range of pediatric populations (McGrath & Brigham, 1992), and may facilitate the identification of children who may benefit from more comprehensive assessment or monitoring. Clinicians should consider establishing standard screening protocols that include assessments of acute pain at multiple points throughout the peri-trauma phase, as both the injury and associated medical treatment can represent painful and potentially traumatic events (Kazak et al., 2006; Marsac et al., 2014). Effective screening during the peri-trauma period would facilitate more targeted prevention or early intervention efforts. Given that PTSS pose a considerable threat to children’s health after injury, further research is needed to examine the feasibility and efficacy of implementing pain assessment tools to enhance screening and prevention approaches.

Funding This work was supported by funding from the Maternal and Child Health Bureau (R40MC00138). Conflicts of interest: None declared.

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variables and thereby provide more accurate conclusions. Additional research is needed to examine the feasibility and efficacy of integrating the CAS or other pain assessment instruments into existing screening protocols for traumatic stress among children. In particular, research comparing the utility of in vivo versus retrospective recall of children’s pain ratings would help to best target screening efforts. Of note, there is a revised version of the FPRS that uses a 0–10 scale and is scored 0-2-4-6-8-10 (Hicks et al., 2001). While variance in ratings on the FPRS-R is still restricted relative to the CAS, future research should examine whether pain assessed by this revised tool predicts PTSS in youth postinjury. Finally, while this study advances our understanding of potential risk factors for the development of PTSS, it did not explore underlying mechanisms of action. Future investigations should include measures of relevant physiological, psychological, and social/environmental factors to test mechanisms and models linking pain and PTSS. A more comprehensive understanding of the complex relationship between acute pain and PTSS could help to improve assessment, prevention, and treatment approaches to promote optimal recovery to pediatric injury.

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Acute Pain and Posttraumatic Stress After Pediatric Injury

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