DEPRESSION AND ANXIETY 32:64–71 (2015)
Research Article THE TEMPORAL RELATIONSHIP BETWEEN MENTAL HEALTH AND DISABILITY AFTER INJURY Stephanie Schweininger, M.Sc.,1,2 David Forbes, Ph.D.,1,2 Mark Creamer, Ph.D.,2 Alexander C. McFarlane, A.O., M.D., F.R.A.N.Z.C.P.,5 Derrick Silove, M.D., F.R.A.N.Z.C.P.,4,6 Richard A. Bryant, Ph.D.,3 and Meaghan L. O’Donnell, Ph.D.1,2 ∗
Objective: This longitudinal study investigated the temporal relationship patterns between disability and mental health after injury, with a focus on posttraumatic stress disorder (PTSD), depression, and anxiety. Method: We conducted a multi-sited longitudinal cohort study with a large sample of hospital patients admitted after injury (N = 1,149, mean age = 37.9, 73.6% male). Data were collected prior to discharge from hospital, and follow-up assessments took place 3 and 12 months postinjury. A cross-lagged structural equation model (SEM) was used to assess the prospective relationship between posttraumatic stress, anxiety, and depression symptoms and disability while controlling for demographic characteristics and objective measures of injury severity. Results: Acute depression significantly predicted 3-month disability, and 3-month PTSD severity significantly predicted 12-month disability. Premorbid disability had a significant effect on acute anxiety, depression, and posttraumatic stress symptoms, and 3-month depression but disability after the injury did not predict 12-month psychopathology. Conclusions: We did not find a reciprocal relationship between disability and psychopathology. Rather we found that depression played a role in early disability while PTSD played a role in contributing to long-term delays in the recovery process. The results of this study highlight the need for mental health screening for symptoms of PTSD and depression in the acute aftermath of trauma, combined with early intervention programs in injury populations. C 2014 Wiley Periodicals, Inc. Depression and Anxiety 32:64–71, 2015. Key words: posttraumatic stress disorder; disability; injury; depression; anxiety; SEM
INTRODUCTION
Physical injury has a major impact on a broad range 1 Australian
Centre for Posttraumatic Mental Health, Carlton, Victoria, Australia 2 Department of Psychiatry, University of Melbourne, Parkville, Victoria, Australia 3 School of Psychology, University of New South Wales, Sydney, New South Wales, Australia 4 Department of Psychiatry, University of New South Wales, Sydney, New South Wales, Australia 5 Centre for Traumatic Stress, University of Adelaide, Adelaide South Australia, Australia 6 Mental Health Centre, Psychiatry Research and Teaching Unit, Liverpool, New South Wales, Australia Contract grant sponsor: National Health and Medical Research Council Program; contract grant number: 568970.
C 2014 Wiley Periodicals, Inc.
of health outcomes and accounts for 16% of all disability worldwide.[1] Disability is an umbrella term that addresses general physical impairments, activity limitations, and social participation restrictions associated with injury. Given the prevalence of disability associated with
∗ Correspondence
to: Meaghan O’Donnell, Australian Centre for Posttraumatic Mental Health, Level 3, 160 Barry street, VIC 3053, Australia. E-mail: [email protected] Received for publication 25 November 2013; Revised 14 April 2014; Accepted 31 May 2014 DOI 10.1002/da.22288 Published online 3 July 2014 in Wiley Online Library (wileyonlinelibrary.com).
Research Article: Mental Health and Disability after Injury
injury worldwide,[2, 3] it is essential that we better understand the factors that contribute to disability after injury. There is growing recognition that psychiatric disorder is a common consequence of injury.[4] In a recent literature review on mental health status after physical injury, Wiseman et al.[5] identified PTSD, depression, and anxiety as the most frequently reported mental health consequences. Prevalence rates range between 18–39% for acute stress disorder and PTSD, and 4–19% for major depression.[6] While it is well established that psychiatric disorders are associated with high levels of disability,[7] the role that these conditions play in driving disability after injury is poorly understood. Previous studies that looked at mental health after injury and its relationship to disability present mixed findings, and methodological issues prevent firm conclusions from being drawn. A few studies found that PTSD predicted later disability after injury[8, 9] but failed to control for other disorders that are likely to be comorbid, i.e. depression and anxiety,[10–13] limiting the generalizability of those results. Taking this into consideration, Thombs et al.[14] reported a significant unique correlation between depression and physical health outcomes, while controlling for symptoms of PTSD. Zatzick et al.[15] on the other hand found that both depression and PTSD were independently associated with a number of functional impairments in adolescents. These studies suggest that there is a relationship between PTSD, depression, and disability after injury, but due to the statistical limitations of regression models they do not provide information about the temporal interaction pattern between psychiatric disorders and disability over time. Does disability drive psychiatric disorders or do psychiatric disorders drive disability? There is emerging evidence of a significant temporal relationship between psychiatric disorders and disability, with high levels of early psychopathology resulting in worse than expected levels of disability 12 months after injury and vice versa.[16] This finding presents an important step toward a better understanding of the temporal connection between mental and physical health. However, it does not answer the question whether this relationship is based on the specific impact of individual psychiatric disorders or general psychopathology. Specifically, does PTSD play a unique role in driving disability or is the detrimental effect of mental health on disability due to the presence of psychiatric disorders in general? To date, only one study has attempted to address the temporal relationship between a specific psychiatric condition and disability after injury. Using a structural equation modeling approach, Ramchand et al.[17] found a reciprocal interaction pattern between PTSD and disability, with both conditions driving each other over time. While this is an important finding, that study does not identify whether PTSD has a unique role in driving disability since it did not examine depression or anxiety concurrently.
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The primary aim of this longitudinal study was to examine the temporal relationship between disability and common psychiatric sequelae of injury. We specifically looked at PTSD, depression, and anxiety after injury. Given that this relationship may change over time, we examined mental health and disability in the first week postinjury, and at 3 and 12 months after injury, using cross-lag structural equation modeling.
METHOD PARTICIPANTS This study is based on data collected between April 2004 and February 2006 in four major trauma hospitals in Australia. Candidates met the inclusion criteria if they were between 16 and 70 years old, proficient in English, and had an injury severe enough to require at least 24 hr of hospital admission. Patients were excluded if they were currently psychotic or suicidal, non-Australian visitors, had cognitive impairment or moderate to severe traumatic brain injury. Baseline assessments took place just prior to discharge from hospital, on average 7.2 days (SD = 9.6) after injury. Patients were reassessed at 3 and 12 months. Structured interviews for PTSD were conducted face to face at hospital, with follow-up interviews being carried out via phone. Self-report measures for anxiety, depression, and disability were sent to all participants, together with a prepaid envelope, at 3 and 12 months. The study was approved by the human ethics research committee at all participating hospitals and the University of Melbourne. A total of 3,371 persons met the inclusion criteria over the twoyear period. From this pool, 1,590 persons were randomly selected and 1,017 provided informed consent and completed the baseline assessment for this study (64%). From this sample, 882 participants (87%) were available for the 3-month follow-up and 775 participants (76%) completed the 12-month follow-up assessment. No differences were found between participants and individuals who refused to participate in the study in respect of age, gender, injury severity, or length of hospitalization. Participants lost to follow-up at 3 months were likely to be on average 4.2 years younger than the mean age of those who did complete the 3 month assessment (34.66 ± 12.95 vs. 38.91 ± 13.58, t(1,162) = –4.6, P < .001). Participants who did not complete the 12-month assessment were more likely to be on average 3.4 years younger than the mean age of those who did complete the second follow-up (35.61 ± 13.00 vs. 39.01 ± 13.68, t(1,162) = –4.1, P < .001). The main causes of injury in our sample were motor vehicle accidents (66%), followed by fall (17%) and assault (6%). The sample consisted predominantly of males (n = 855; 74%). Average age was 37.9 years (SD = 13.6) with a mean injury severity score (ISS) of 11.0 (SD = 7.9). Mean length of stay in hospital was 12.4 days (SD = 12.9).
MEASURES Disability. Preinjury, 3-month and 12-month disability were measured with the World Health Organization Disability Assessment Schedule II (WHODAS II[18] ). The WHODAS II is a reliable crosscultural measure for disability across a variety of disorders.[19] The self-administered 12-item version was used to measure overall functioning within the past 30 days. Because our focus was on physical disability, one item was excluded (S5 “How much have you been emotionally affected by your health problems?”). Answers are given on a 5point Likert scale. A total summary score was calculated using complex scoring, which created a metric ranging from 0 ( = no disability) to 100 ( = full disability). Preinjury disability was assessed retrospectively, Depression and Anxiety
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instructing participants to complete the questionnaire regarding their status in the two weeks prior to their injury. Posttraumatic Stress Symptoms. Posttraumatic stress symptoms were assessed using the Clinician Administered PTSD Scale (CAPS[20] ). The CAPS is widely considered the gold standard in PTSD assessment and has shown excellent psychometric values.[21] This structured interview consists of 17 items that correspond to the DSM-IV criteria for PTSD. Symptom frequency and intensity are measured independently on a 0–4 Likert scale. For our analysis, the total severity score was used, created by summing up frequency and intensity scores with total scores ranging from 0–136. The CAPS was administered by research assistants trained in the CAPS protocol by MOD. All assessments were audio-recorded to assess adherence to the protocol and 5% of all CAPS interviews were randomly selected to inter-rater reliability testing. The diagnostic consistency for PTSD with the CAPS was 1.00 at 3 months and 0.98 at 12 months. Anxiety and Depression. The Hospital Anxiety and Depression Scale (HADS[22] ) was used to measure anxiety and depression symptoms and severity. This self-report questionnaire was developed for use among patients with ill health in the general population, focusing on mental rather than physical correlates of depression and anxiety. Both scales consist of seven items. Responses are given on a 4-point Likert scale ranging from 0 to 3 with a maximum total score of 21 on each scale. Higher scores indicate higher symptom severity. The HADS has been widely used in previous research and showed excellent psychometric values.[23] Other Covariates. To control for possible influences on the relationship between disability and mental health conditions, we included the following covariates in our model. Injury Characteristics. Injury Severity Score[24] and length of stay in hospital were obtained from patients’ hospital records. The ISS is a well-established anatomical scoring system that provides an overall severity score for varying degrees of injuries, ranging from 0 to 75. A lower score indicates less severe injuries. Pain. Taking into account previous research findings reporting a strong connection between PTSD, pain, and disability[25, 26] pain severity was included as an additional covariate. Pain severity was assessed via visual analog scale.[27] Values ranged from 0 to 10, measuring acute pain at hospital admission, and average pain during the past two weeks for both follow-up assessments. Demographic Factors. Participants’ age and gender were assessed by self-report and interviewer observation.
STATISTICAL ANALYSIS A cross-lagged longitudinal panel design was applied to the data to assess the relationship between PTSD, depression, and anxiety with disability, as well as the interaction between mental health symptoms over time. Structural equation modeling (SEM) was employed, using Mplus version 7.[28] Structural equation modeling provides a sophisticated way of analyzing data in complex models. Advantages of SEM over multiple regression analysis include the ability to test multiple relationships simultaneously and implement models with numerous dependent variables. The use of SEM in a longitudinal study design further allows researchers to investigate temporal relationship patterns between variables. The baseline model estimated paths from each latent variable at a follow-up wave to all latent variables from the prior wave. A random parceling technique was used to create latent variables for disability, depression, and anxiety. An advantage of using parcels rather than individual items as indicators of latent variables is improved reliability.[29] Each latent variable was constructed by three item parcels representing the average score of two to four items. PTSD was represented as a latent variable as indicated by the CAPS subscales reexperiencing, avoidance, and hyperarousal. Factor loadings were freely estimated for each indiDepression and Anxiety
cator but fixed to be invariant across waves. Latent factor variance was fixed to one for model identification. Residuals were correlated with themselves across all waves. PTSD, depression, and anxiety at baseline were regressed on preinjury disability. Autoregressive paths were estimated between waves and from baseline to 12-month assessment for all variables. Correlations between the residuals of PTSD, anxiety, depression, and disability were estimated within each follow-up wave. To control for a variety of possible influences, PTSD, depression, anxiety, and disability were regressed on all covariates at each wave. Covariates were allowed to correlate with each other. Group comparisons were conducted using IBM SPSS version 20. Model results were estimated using robust maximum likelihood (MLR) estimation. MLR uses a sandwich estimator, which provides accurate standard errors, even in nonnormally distributed data.[30] The MLR estimator produces the same parameter estimates as maximumlikelihood estimation.[31] The well-established cut-off value of CFI > .95[32] and the more recently suggested threshold of RMSEA < .05 (ISS[33] ) were considered as indicators of good model fit.
RESULTS Descriptive data for disability and mental health over time are presented in Table 1. Our final model fit the data well (χ 2 (723) = 1,805, P < .001; CFI = .951, RMSEA = .036, SRMR = .062). For the purpose of clarity, Fig. 1 only shows direct autoregressive- and cross-lagged pathways, as well as standardized significant path coefficients. Significant autoregressive paths were found for all variables, with prior scores on one scale influencing subsequent disability and mental health within the same construct across time. The only exception to this pattern was a nonsignificant path from baseline depression to depression at 12 months. Associations between the covariates (including pain severity) included in our model, psychiatric disorders, and disability are displayed in Table 2. Table 3 shows the correlations between disability and mental health within each point of assessment. The variables included in our model explained 55% of TABLE 1. Descriptive data for disability and psychiatric disorders over time Variable Disability Preinjury disability Disability 3 months Disability 12 months PTSD PTSD baseline PTSD 3 months PTSD 12 months Depression Depression baseline Depression 3 months Depression 12 months Anxiety Anxiety baseline Anxiety 3 months Anxiety 12 months
Mean
Standard deviation
7.49 30.07 20.98
12.46 22.08 20.54
18.21 20.71 19.29
16.67 21.38 21.90
4.89 4.87 4.51
4.00 4.10 4.16
5.20 5.81 6.07
4.14 4.48 4.47
Note: PTSD, posttraumatic stress disorder.
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Figure 1. The cross-lag relationships between posttraumatic stress disorder severity, depression severity, anxiety severity, and disability severity over the first 12 months after serious injury.
variance in long-term disability, 68% in long-term PTSD, 55% in anxiety and 56% of variance in depression at 12 months.
DISABILITY
As expected, higher premorbid disability levels resulted in more severe short- and long-term disability. High premorbid disability scores were also associated with a significant increase on all mental health variables at baseline and increased depression at 3 months postinjury. Disability, at 3 months, however, had no significant impact on long-term mental health.
POSTTRAUMATIC STRESS DISORDER
PTSD was the only mental health variable to significantly contribute to long-term disability (3-month PTSD on 12-month disability). Higher levels of PTSD symptoms during hospitalization were associated with increased levels of depression and anxiety at 3 months. This relationship was also found for the subsequent follow-up wave from 3 to 12 months. Depression and anxiety did not present a significant impact on short- or long-term PTSD.
DEPRESSION
High levels of depression in hospital significantly contributed to short-term disability. However, no significant effect was found for 3-month depression on longterm disability. Depression had no significant impact on PTSD or anxiety at subsequent waves. ANXIETY
Neither short- nor long-term anxiety directly contributed to later disability, PTSD, or depression.
DISCUSSION This longitudinal multi-sited cohort study investigated the unique interrelations between disability and PTSD, depression, and anxiety in a complex structural equation model. To our knowledge, this is the largest study to concurrently test the pathways between disability and mental health in injury survivors using a cross-lag approach. The statistical method used in this study allowed for the investigation of multiple pathways at the same time and addresses the urgent need to further investigate the role that mental health plays in driving disability after injury.[5, 16] Our findings demonstrated interesting temporal interactions between mental health and disability in Depression and Anxiety
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TABLE 2. Association of covariates with disability, depression, anxiety, and PTSD Post-injury Covariate
Pre-Dis
Anx
Hospital Dep
Gender Age ISS Days in hospital Pain Severity
−.01 .05 −.06 −.02 .17**
.09* −.09* −.02 .07 .37**
.08* −.06 .02 .05 .35**
PTSD
Dis
.16** −.15** .01 .13** .32**
.01 .05 .00 .25** .47**
3 month Anx Dep .03 −.06* −.04 −.04 .28**
−.04 .00 −.02 .04 .33**
PTSD
Dis
.07* −.07* .01 −.05 .26**
−.07* .04 −.02 .14** .42**
12 month Anx Dep .00 .01 .04 .02 .19**
−.07* .05* .04 .08* .27**
PTSD −.01 −.03 .07* −.00 .15**
Note: Numbers denote standardized path coefficients in the final model. Pre-Dis, disability prior to injury; Dis, disability; Anx, anxiety; Dep, depression; PTSD, posttraumatic stress disorder. ∗ P < .05, ∗∗ P < .001.
injury survivors. In general, psychiatric symptoms played a clear role in driving disability over the entire 12-month period. Disability, however, only affected the psychiatric response in the short term. While depression symptoms played an important role in driving short-term disability, it was PTSD that stood apart in this study. PTSD had a unique impact on both disability and mental health, in the short- and long term. Our findings on premorbid disability are in accordance with a number of studies regarding mental[34] and physical[35, 36] health outcomes. A possible explanation for the detrimental effects of premorbid disability on later health might be that elevated levels of vulnerability in previously impaired individuals interfere with the general recovery process. Unlike Ramchand et al.,[17] our results did not indicate a continuous reciprocal relationship between PTSD and disability over time. In contrast to their findings, we found that PTSD drove long-term, but not short-term disability, and 3month disability did not have a significant long-term effect on 12-month PTSD in our study. This difference may be a function of our study including anxiety and depression in our model and controlling for pain. While disability had little impact on mental health, psychopathology, however, drove disability over time. Depression showed a high impact on short-term disability, although its impact on long-term disability was nonsignificant. Our findings replicate the results reported by Thombs et al.[14] regarding short-term depression. Also consistent with our results, Kosloski et al.[37] found no significant effect of depression on long-term
self-reported health. One possible explanation for the detrimental effect of depression on short-term, but not long-term physical health may be impaired adherence to medical treatment and self-care in the early phase after injury.[38] Depression severity and adherence to medical treatment are associated in a gradient fashion, with more severe depression symptoms causing poorer adherence early on.[39] High levels of depression may have therefore slowed down the physical recovery process. Unlike depression, anxiety did not have an independent significant effect on disability or mental health. Given that the HADS anxiety measure targets general anxiety symptoms, such as worry and panic,[22, 40] this result may not be surprising, as the link between generalized anxiety disorder and disability has been found to be relatively weak.[41] A possible explanation for the differing relationship between general anxiety and disability, as opposed to PTSD and disability, might be a variation in underlying complex psychobiology patterns (see [42] ) Posttraumatic stress disorder symptoms played a unique role in the aftermath of injury as this was the only mental health variable that contributed to longterm disability. Additionally, PTSD had a unique impact on general mental health, as indicated by its influence on depression and anxiety symptoms over time. In accordance with our results, PTSD was found to be significantly related to a variety of short- and longterm physical and mental health outcomes in a number of studies.[43–45] There is something uniquely damaging about high levels of PTSD symptoms in the aftermath of injury.
TABLE 3. Correlations between psychiatric disorders and disability within waves Time 3 months
Baseline
12 months
Variable
PTSD
Dep
Anx
PTSD
Dep
Anx
PTSD
Dep
Anx
Dep Anx Dis
.49** .62**
.77**
-
.43** .54** .38**
.71** .57**
.41**
.61** .56** .46**
.84** .74**
.61**
Note: Correlations between mental health variables and disability were calculated for the 3- and 12-month follow-up assessments only. PTSD, post-traumatic stress disorder; Dep, major depression; Anx, anxiety; Dis, disability. ∗∗ P < .001. Depression and Anxiety
Research Article: Mental Health and Disability after Injury
Previous research has shown that, compared to other psychiatric disorders, PTSD carries a particularly high level of disability that results in increased health care costs in affected populations.[46] There are several possible explanations for this relationship. First, the avoidance behavior patterns characteristic of PTSD present one possible mechanism.[47] Avoidance of reminders of the traumatic event may prevent the individual from reengaging in their preinjury life, which in turn increases disability levels. There is evidence to suggest avoidance associated with PTSD increases over time[48] that may explain the impact on long-term disability of PTSD in our study. Second, ongoing levels of elevated arousal are known to put individuals at risk for sensitization (see [49] ) that is defined as “an increase in response to a stimulus as a function of repeated representations of that stimulus” ([49] , p.106). Sensitization has been proposed as a mechanism by which PTSD symptoms escalate over time that in turn contributes to higher levels of disability. Furthermore, similar processes have been forwarded to explain the relationship between PTSD and pain, which also may contribute disability over time.[16, 50] Our findings have several implications for future research and treatment of injury populations. The results provide further evidence of the need for early intervention with individuals reporting symptoms of PTSD and depression after injury to prevent long-term physical and mental disability. Although this claim has been made before, efforts to put these recommendations into practice are rare (see [5] ), and have yet failed to show consistent improvement through early treatment (see [51] ). Early intervention using cognitive-behavioral therapy (CBT) has shown promising results in previous research (e.g. [52] ). In a study published by Zatzick et al.,[53] stepped early intervention patients reported significantly reduced PTSD symptoms, and significantly improved physical functioning compared to the usual care condition. Future research should identify programs that can be implemented as routine treatment for individuals scoring high on PTSD and depression symptoms prior to discharge. Such programs would aim to effectively address patients’ needs after injury, improve mental health recovery trajectories, and prevent chronic disability. As a precursor to intervention, effective screening methods are needed to identify individuals that are likely to develop ongoing mental health issues following injury. There have been a number of screens developed in this population that identify those at risk for developing mental health disorders (e.g. [54] ) and evidence that early intervention can prevent and treat early presentations of psychiatric disorder after injury (e.g. [52] ). Given that the majority of individuals with PTSD and other psychiatric disorder do not seek mental health treatment,[55] early screening is crucial to prevent chronic disability. This study has certain limitations. Our sample consisted predominantly of male injury survivors (74%), reducing the generalizability of our results to female injury or other trauma populations. Furthermore, depression, anxiety, and disability were assessed via self-administered
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questionnaires rather than structured clinical interview. Similarly, disability was assessed via self-report and the study may have benefited from the use of an objective measure, such as return to work. Self-report questionnaires are frequently used in psychological research, and have several advantages, but may also be at risk of bias.[43] Finally, the model tested was not a complete model of the factors that contribute to disability after injury. Indeed, our model only accounted for 55% of the variance in long-term disability. It is well known that many variables contribute to disability directly or indirectly such as a past psychiatric history, prior trauma history, compensation status, and social support. While our model did control some variables that we identified as theoretically important to our question, we were unable to include all contributors to disability in the model. Readers need to therefore view our findings with this understanding. Despite these limitations, our findings provide further important insights into the complex relationship between disability and mental health. High levels of early psychopathology resulted in worse than expected recovery after injury over the entire 12-month period, while the impact of disability on mental health was limited to the direct aftermath of injury. PTSD was found to uniquely drive long-term disability, providing additional evidence for the importance of targeting PTSD symptoms as early as possible in injured populations. Given the frequency with which injury occurs, it is important to understand the complex mechanisms underlying the recovery process. Early screening and intervention programs should be adopted routinely for injury victims, focusing on PTSD as well as depression symptoms. The current results have the potential to enhance primary care interventions and the prevention of ongoing chronic disability in exposed individuals. Acknowledgments. The authors gratefully acknowledge all the participants involved in this study. This study was supported by a National Health and Medical Research Council Program Grant (568970). Conflict of interest. The authors have no conflicts of interest to report.
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28. Muth´en LK, Muth´en BO. Mplus. Verson 3.1 ed. Los Angeles, CA: Muth´en & Muth´en; 2004. 29. Coffman DL, MacCallum RC. Using parcels to convert path analysis models into latent variable models. Multivar Behav Res 2005;40(2):235–259. 30. Wu JY, Kwok O. Using SEM to analyze complex survey data: a comparison between design-based single-level and model-based multilevel approaches. Struct Equ Modeling 2012;19(1):16–35. 31. Hox JJ, Maas CJ, Brinkhuis MJ. The effect of estimation method and sample size in multilevel structural equation modeling. Statistica Neerlandica 2010;64(2):157–170. 32. Hu L, Bentler PM. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Modeling 1999;6(1):1–55. 33. Iacobucci D. Structural equations modeling: fit indices, sample size, and advanced topics. J Consumer Psychol 2010;20(1):90–98. 34. McCusker J, Cole M, Ciampi A, Latimer E, Windholz S, Belzile E. Major depression in older medical inpatients predicts poor physical and mental health status over 12 months. Gen Hosp Psychiatry 2007;29(4):340–348. 35. Kirk-Sanchez NJ. The importance of psychosocial factors in determining disability and perceived health in a group of older Hispanic-Americans recovering from hip fracture. J Geriatric Phys Ther 2003;26(2):3–8. 36. Spratt N, Wang Y, Levi C, Ng K, Evans M, Fisher J. A prospective study of predictors of prolonged hospital stay and disability after stroke. J Clin Neurosci 2003;10(6):665–669. 37. Kosloski K, Stull DE, Kercher K, Van Dussen DJ. Longitudinal analysis of the reciprocal effects of self-assessed global health and depressive symptoms. J Gerontol S B 2005;60(6):P296–P303. 38. DiMatteo MR, Lepper HS, Croghan TW. Depression is a risk factor for noncompliance with medical treatment: meta-analysis of the effects of anxiety and depression on patient adherence. Archiv Intern Med 2000;160(14):2101–2107. 39. Rieckmann N, Gerin W, Kronish IM, et al. Course of depressive symptoms and medication adherence after acute coronary syndromes an electronic medication monitoring study. J Am College Cardiol 2006;48(11):2218–2222. 40. Olssøn I, Mykletun A, Dahl A. The Hospital Anxiety and Depression Rating Scale: a cross-sectional study of psychometrics and case finding abilities in general practice. BMC Psychiatry 2005;5(1):46. 41. Sherbourne CD, Sullivan G, Craske MG, et al. Functioning and disability levels in primary care out-patients with one or more anxiety disorders. Psychol Med 2010;40(12):2059. 42. Kim J, Gorman J. The psychobiology of anxiety. Clin Neurosc Res 2005;4(5):335–347. 43. Zatzick DF, Jurkovich GJ, Gentilello L, Wisner D, Rivara FP. Posttraumatic stress, problem drinking, and functional outcomes after injury. Arch Surg 2002;137(2):200–205. 44. Sareen J, Cox BJ, Stein MB, Afifi TO, Fleet C, Asmundson GJG. Physical and mental comorbidity, disability, and suicidal behavior associated with posttraumatic stress disorder in a large community sample. Psychosom Med 2007;69(3):242–248. 45. Pacella ML, Hruska B, Delahanty DL. The physical health consequences of PTSD and PTSD symptoms: a meta-analytic review. J Anxiety Disord 2013;27(1):33–46. 46. Australian Centre for Posttraumatic Mental Health. Australian Guidelines for the Treatment of Acute Stress Disorder and Posttraumatic Stress Disorder. Melbourne, Victoria: ACPMH; 2013. 47. Geisser ME, Roth RS, Bachman JE, Eckert TA. The relationship between symptoms of post-traumatic stress disorder and pain, affective disturbance and disability among patients with accident and non-accident related pain. Pain 1996;66(2–3):207–214.
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48. O’Donnell ML, Elliott P, Lau W, Creamer M. PTSD symptom trajectories: from early to chronic response. Behav Res Ther 2007;45:601–606. 49. Overmier JB. Sensitization, conditioning, and learning: can they help us understand somatization and disability? Scand J Psychol 2002;43(2):105–112. 50. Liedl A, O’Donnell M, Creamer M, et al. Support for the mutual maintenance of pain and post-traumatic stress disorder symptoms. Psychol Med 2010;40(7):1215–1223. 51. Kearns MC, Ressler KJ, Zatzick D, Rothbaum BO. Early interventions for PTSD: a review. Depress Anxiety 2012;29(10):833–842. 52. O’Donnell ML, Lau W, Tipping S, et al. Stepped early psychological intervention for posttraumatic stress disorder, other anxiety
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disorders and depression and following serious injury. J Traum Stress 2012;25:125–133. 53. Zatzick DF, Roy-Byrne P, Russo J, et al. A randomized effectiveness trial of stepped collaborative care foracutely injured trauma survivors. Archiv Gen Psychiatry 2004;61(5):498–506. 54. O’Donnell ML, Creamer MC, Parslow R, et al. A predictive screening index for posttraumatic stress disorder and depression following traumatic injury. J Consult Clin Psychol 2008;76(6):923–932. 55. Wang PS, Berglund P, Olfson M, Pincus HA, Wells KB, Kessler RC. Failure and delay in initial treatment contact after first onset of mental disorders in the National Comorbidity Survey Replication. Archiv Gen Psychiatry 2005;62(6):603–613.
Depression and Anxiety
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Research Article THE TEMPORAL RELATIONSHIP BETWEEN MENTAL HEALTH AND DISABILITY AFTER INJURY Stephanie Schweininger, M.Sc.,1,2 David Forbes, Ph.D.,1,2 Mark Creamer, Ph.D.,2 Alexander C. McFarlane, A.O., M.D., F.R.A.N.Z.C.P.,5 Derrick Silove, M.D., F.R.A.N.Z.C.P.,4,6 Richard A. Bryant, Ph.D.,3 and Meaghan L. O’Donnell, Ph.D.1,2 ∗
Objective: This longitudinal study investigated the temporal relationship patterns between disability and mental health after injury, with a focus on posttraumatic stress disorder (PTSD), depression, and anxiety. Method: We conducted a multi-sited longitudinal cohort study with a large sample of hospital patients admitted after injury (N = 1,149, mean age = 37.9, 73.6% male). Data were collected prior to discharge from hospital, and follow-up assessments took place 3 and 12 months postinjury. A cross-lagged structural equation model (SEM) was used to assess the prospective relationship between posttraumatic stress, anxiety, and depression symptoms and disability while controlling for demographic characteristics and objective measures of injury severity. Results: Acute depression significantly predicted 3-month disability, and 3-month PTSD severity significantly predicted 12-month disability. Premorbid disability had a significant effect on acute anxiety, depression, and posttraumatic stress symptoms, and 3-month depression but disability after the injury did not predict 12-month psychopathology. Conclusions: We did not find a reciprocal relationship between disability and psychopathology. Rather we found that depression played a role in early disability while PTSD played a role in contributing to long-term delays in the recovery process. The results of this study highlight the need for mental health screening for symptoms of PTSD and depression in the acute aftermath of trauma, combined with early intervention programs in injury populations. C 2014 Wiley Periodicals, Inc. Depression and Anxiety 32:64–71, 2015. Key words: posttraumatic stress disorder; disability; injury; depression; anxiety; SEM
INTRODUCTION
Physical injury has a major impact on a broad range 1 Australian
Centre for Posttraumatic Mental Health, Carlton, Victoria, Australia 2 Department of Psychiatry, University of Melbourne, Parkville, Victoria, Australia 3 School of Psychology, University of New South Wales, Sydney, New South Wales, Australia 4 Department of Psychiatry, University of New South Wales, Sydney, New South Wales, Australia 5 Centre for Traumatic Stress, University of Adelaide, Adelaide South Australia, Australia 6 Mental Health Centre, Psychiatry Research and Teaching Unit, Liverpool, New South Wales, Australia Contract grant sponsor: National Health and Medical Research Council Program; contract grant number: 568970.
C 2014 Wiley Periodicals, Inc.
of health outcomes and accounts for 16% of all disability worldwide.[1] Disability is an umbrella term that addresses general physical impairments, activity limitations, and social participation restrictions associated with injury. Given the prevalence of disability associated with
∗ Correspondence
to: Meaghan O’Donnell, Australian Centre for Posttraumatic Mental Health, Level 3, 160 Barry street, VIC 3053, Australia. E-mail: [email protected] Received for publication 25 November 2013; Revised 14 April 2014; Accepted 31 May 2014 DOI 10.1002/da.22288 Published online 3 July 2014 in Wiley Online Library (wileyonlinelibrary.com).
Research Article: Mental Health and Disability after Injury
injury worldwide,[2, 3] it is essential that we better understand the factors that contribute to disability after injury. There is growing recognition that psychiatric disorder is a common consequence of injury.[4] In a recent literature review on mental health status after physical injury, Wiseman et al.[5] identified PTSD, depression, and anxiety as the most frequently reported mental health consequences. Prevalence rates range between 18–39% for acute stress disorder and PTSD, and 4–19% for major depression.[6] While it is well established that psychiatric disorders are associated with high levels of disability,[7] the role that these conditions play in driving disability after injury is poorly understood. Previous studies that looked at mental health after injury and its relationship to disability present mixed findings, and methodological issues prevent firm conclusions from being drawn. A few studies found that PTSD predicted later disability after injury[8, 9] but failed to control for other disorders that are likely to be comorbid, i.e. depression and anxiety,[10–13] limiting the generalizability of those results. Taking this into consideration, Thombs et al.[14] reported a significant unique correlation between depression and physical health outcomes, while controlling for symptoms of PTSD. Zatzick et al.[15] on the other hand found that both depression and PTSD were independently associated with a number of functional impairments in adolescents. These studies suggest that there is a relationship between PTSD, depression, and disability after injury, but due to the statistical limitations of regression models they do not provide information about the temporal interaction pattern between psychiatric disorders and disability over time. Does disability drive psychiatric disorders or do psychiatric disorders drive disability? There is emerging evidence of a significant temporal relationship between psychiatric disorders and disability, with high levels of early psychopathology resulting in worse than expected levels of disability 12 months after injury and vice versa.[16] This finding presents an important step toward a better understanding of the temporal connection between mental and physical health. However, it does not answer the question whether this relationship is based on the specific impact of individual psychiatric disorders or general psychopathology. Specifically, does PTSD play a unique role in driving disability or is the detrimental effect of mental health on disability due to the presence of psychiatric disorders in general? To date, only one study has attempted to address the temporal relationship between a specific psychiatric condition and disability after injury. Using a structural equation modeling approach, Ramchand et al.[17] found a reciprocal interaction pattern between PTSD and disability, with both conditions driving each other over time. While this is an important finding, that study does not identify whether PTSD has a unique role in driving disability since it did not examine depression or anxiety concurrently.
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The primary aim of this longitudinal study was to examine the temporal relationship between disability and common psychiatric sequelae of injury. We specifically looked at PTSD, depression, and anxiety after injury. Given that this relationship may change over time, we examined mental health and disability in the first week postinjury, and at 3 and 12 months after injury, using cross-lag structural equation modeling.
METHOD PARTICIPANTS This study is based on data collected between April 2004 and February 2006 in four major trauma hospitals in Australia. Candidates met the inclusion criteria if they were between 16 and 70 years old, proficient in English, and had an injury severe enough to require at least 24 hr of hospital admission. Patients were excluded if they were currently psychotic or suicidal, non-Australian visitors, had cognitive impairment or moderate to severe traumatic brain injury. Baseline assessments took place just prior to discharge from hospital, on average 7.2 days (SD = 9.6) after injury. Patients were reassessed at 3 and 12 months. Structured interviews for PTSD were conducted face to face at hospital, with follow-up interviews being carried out via phone. Self-report measures for anxiety, depression, and disability were sent to all participants, together with a prepaid envelope, at 3 and 12 months. The study was approved by the human ethics research committee at all participating hospitals and the University of Melbourne. A total of 3,371 persons met the inclusion criteria over the twoyear period. From this pool, 1,590 persons were randomly selected and 1,017 provided informed consent and completed the baseline assessment for this study (64%). From this sample, 882 participants (87%) were available for the 3-month follow-up and 775 participants (76%) completed the 12-month follow-up assessment. No differences were found between participants and individuals who refused to participate in the study in respect of age, gender, injury severity, or length of hospitalization. Participants lost to follow-up at 3 months were likely to be on average 4.2 years younger than the mean age of those who did complete the 3 month assessment (34.66 ± 12.95 vs. 38.91 ± 13.58, t(1,162) = –4.6, P < .001). Participants who did not complete the 12-month assessment were more likely to be on average 3.4 years younger than the mean age of those who did complete the second follow-up (35.61 ± 13.00 vs. 39.01 ± 13.68, t(1,162) = –4.1, P < .001). The main causes of injury in our sample were motor vehicle accidents (66%), followed by fall (17%) and assault (6%). The sample consisted predominantly of males (n = 855; 74%). Average age was 37.9 years (SD = 13.6) with a mean injury severity score (ISS) of 11.0 (SD = 7.9). Mean length of stay in hospital was 12.4 days (SD = 12.9).
MEASURES Disability. Preinjury, 3-month and 12-month disability were measured with the World Health Organization Disability Assessment Schedule II (WHODAS II[18] ). The WHODAS II is a reliable crosscultural measure for disability across a variety of disorders.[19] The self-administered 12-item version was used to measure overall functioning within the past 30 days. Because our focus was on physical disability, one item was excluded (S5 “How much have you been emotionally affected by your health problems?”). Answers are given on a 5point Likert scale. A total summary score was calculated using complex scoring, which created a metric ranging from 0 ( = no disability) to 100 ( = full disability). Preinjury disability was assessed retrospectively, Depression and Anxiety
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instructing participants to complete the questionnaire regarding their status in the two weeks prior to their injury. Posttraumatic Stress Symptoms. Posttraumatic stress symptoms were assessed using the Clinician Administered PTSD Scale (CAPS[20] ). The CAPS is widely considered the gold standard in PTSD assessment and has shown excellent psychometric values.[21] This structured interview consists of 17 items that correspond to the DSM-IV criteria for PTSD. Symptom frequency and intensity are measured independently on a 0–4 Likert scale. For our analysis, the total severity score was used, created by summing up frequency and intensity scores with total scores ranging from 0–136. The CAPS was administered by research assistants trained in the CAPS protocol by MOD. All assessments were audio-recorded to assess adherence to the protocol and 5% of all CAPS interviews were randomly selected to inter-rater reliability testing. The diagnostic consistency for PTSD with the CAPS was 1.00 at 3 months and 0.98 at 12 months. Anxiety and Depression. The Hospital Anxiety and Depression Scale (HADS[22] ) was used to measure anxiety and depression symptoms and severity. This self-report questionnaire was developed for use among patients with ill health in the general population, focusing on mental rather than physical correlates of depression and anxiety. Both scales consist of seven items. Responses are given on a 4-point Likert scale ranging from 0 to 3 with a maximum total score of 21 on each scale. Higher scores indicate higher symptom severity. The HADS has been widely used in previous research and showed excellent psychometric values.[23] Other Covariates. To control for possible influences on the relationship between disability and mental health conditions, we included the following covariates in our model. Injury Characteristics. Injury Severity Score[24] and length of stay in hospital were obtained from patients’ hospital records. The ISS is a well-established anatomical scoring system that provides an overall severity score for varying degrees of injuries, ranging from 0 to 75. A lower score indicates less severe injuries. Pain. Taking into account previous research findings reporting a strong connection between PTSD, pain, and disability[25, 26] pain severity was included as an additional covariate. Pain severity was assessed via visual analog scale.[27] Values ranged from 0 to 10, measuring acute pain at hospital admission, and average pain during the past two weeks for both follow-up assessments. Demographic Factors. Participants’ age and gender were assessed by self-report and interviewer observation.
STATISTICAL ANALYSIS A cross-lagged longitudinal panel design was applied to the data to assess the relationship between PTSD, depression, and anxiety with disability, as well as the interaction between mental health symptoms over time. Structural equation modeling (SEM) was employed, using Mplus version 7.[28] Structural equation modeling provides a sophisticated way of analyzing data in complex models. Advantages of SEM over multiple regression analysis include the ability to test multiple relationships simultaneously and implement models with numerous dependent variables. The use of SEM in a longitudinal study design further allows researchers to investigate temporal relationship patterns between variables. The baseline model estimated paths from each latent variable at a follow-up wave to all latent variables from the prior wave. A random parceling technique was used to create latent variables for disability, depression, and anxiety. An advantage of using parcels rather than individual items as indicators of latent variables is improved reliability.[29] Each latent variable was constructed by three item parcels representing the average score of two to four items. PTSD was represented as a latent variable as indicated by the CAPS subscales reexperiencing, avoidance, and hyperarousal. Factor loadings were freely estimated for each indiDepression and Anxiety
cator but fixed to be invariant across waves. Latent factor variance was fixed to one for model identification. Residuals were correlated with themselves across all waves. PTSD, depression, and anxiety at baseline were regressed on preinjury disability. Autoregressive paths were estimated between waves and from baseline to 12-month assessment for all variables. Correlations between the residuals of PTSD, anxiety, depression, and disability were estimated within each follow-up wave. To control for a variety of possible influences, PTSD, depression, anxiety, and disability were regressed on all covariates at each wave. Covariates were allowed to correlate with each other. Group comparisons were conducted using IBM SPSS version 20. Model results were estimated using robust maximum likelihood (MLR) estimation. MLR uses a sandwich estimator, which provides accurate standard errors, even in nonnormally distributed data.[30] The MLR estimator produces the same parameter estimates as maximumlikelihood estimation.[31] The well-established cut-off value of CFI > .95[32] and the more recently suggested threshold of RMSEA < .05 (ISS[33] ) were considered as indicators of good model fit.
RESULTS Descriptive data for disability and mental health over time are presented in Table 1. Our final model fit the data well (χ 2 (723) = 1,805, P < .001; CFI = .951, RMSEA = .036, SRMR = .062). For the purpose of clarity, Fig. 1 only shows direct autoregressive- and cross-lagged pathways, as well as standardized significant path coefficients. Significant autoregressive paths were found for all variables, with prior scores on one scale influencing subsequent disability and mental health within the same construct across time. The only exception to this pattern was a nonsignificant path from baseline depression to depression at 12 months. Associations between the covariates (including pain severity) included in our model, psychiatric disorders, and disability are displayed in Table 2. Table 3 shows the correlations between disability and mental health within each point of assessment. The variables included in our model explained 55% of TABLE 1. Descriptive data for disability and psychiatric disorders over time Variable Disability Preinjury disability Disability 3 months Disability 12 months PTSD PTSD baseline PTSD 3 months PTSD 12 months Depression Depression baseline Depression 3 months Depression 12 months Anxiety Anxiety baseline Anxiety 3 months Anxiety 12 months
Mean
Standard deviation
7.49 30.07 20.98
12.46 22.08 20.54
18.21 20.71 19.29
16.67 21.38 21.90
4.89 4.87 4.51
4.00 4.10 4.16
5.20 5.81 6.07
4.14 4.48 4.47
Note: PTSD, posttraumatic stress disorder.
Research Article: Mental Health and Disability after Injury
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Figure 1. The cross-lag relationships between posttraumatic stress disorder severity, depression severity, anxiety severity, and disability severity over the first 12 months after serious injury.
variance in long-term disability, 68% in long-term PTSD, 55% in anxiety and 56% of variance in depression at 12 months.
DISABILITY
As expected, higher premorbid disability levels resulted in more severe short- and long-term disability. High premorbid disability scores were also associated with a significant increase on all mental health variables at baseline and increased depression at 3 months postinjury. Disability, at 3 months, however, had no significant impact on long-term mental health.
POSTTRAUMATIC STRESS DISORDER
PTSD was the only mental health variable to significantly contribute to long-term disability (3-month PTSD on 12-month disability). Higher levels of PTSD symptoms during hospitalization were associated with increased levels of depression and anxiety at 3 months. This relationship was also found for the subsequent follow-up wave from 3 to 12 months. Depression and anxiety did not present a significant impact on short- or long-term PTSD.
DEPRESSION
High levels of depression in hospital significantly contributed to short-term disability. However, no significant effect was found for 3-month depression on longterm disability. Depression had no significant impact on PTSD or anxiety at subsequent waves. ANXIETY
Neither short- nor long-term anxiety directly contributed to later disability, PTSD, or depression.
DISCUSSION This longitudinal multi-sited cohort study investigated the unique interrelations between disability and PTSD, depression, and anxiety in a complex structural equation model. To our knowledge, this is the largest study to concurrently test the pathways between disability and mental health in injury survivors using a cross-lag approach. The statistical method used in this study allowed for the investigation of multiple pathways at the same time and addresses the urgent need to further investigate the role that mental health plays in driving disability after injury.[5, 16] Our findings demonstrated interesting temporal interactions between mental health and disability in Depression and Anxiety
Schweininger et al.
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TABLE 2. Association of covariates with disability, depression, anxiety, and PTSD Post-injury Covariate
Pre-Dis
Anx
Hospital Dep
Gender Age ISS Days in hospital Pain Severity
−.01 .05 −.06 −.02 .17**
.09* −.09* −.02 .07 .37**
.08* −.06 .02 .05 .35**
PTSD
Dis
.16** −.15** .01 .13** .32**
.01 .05 .00 .25** .47**
3 month Anx Dep .03 −.06* −.04 −.04 .28**
−.04 .00 −.02 .04 .33**
PTSD
Dis
.07* −.07* .01 −.05 .26**
−.07* .04 −.02 .14** .42**
12 month Anx Dep .00 .01 .04 .02 .19**
−.07* .05* .04 .08* .27**
PTSD −.01 −.03 .07* −.00 .15**
Note: Numbers denote standardized path coefficients in the final model. Pre-Dis, disability prior to injury; Dis, disability; Anx, anxiety; Dep, depression; PTSD, posttraumatic stress disorder. ∗ P < .05, ∗∗ P < .001.
injury survivors. In general, psychiatric symptoms played a clear role in driving disability over the entire 12-month period. Disability, however, only affected the psychiatric response in the short term. While depression symptoms played an important role in driving short-term disability, it was PTSD that stood apart in this study. PTSD had a unique impact on both disability and mental health, in the short- and long term. Our findings on premorbid disability are in accordance with a number of studies regarding mental[34] and physical[35, 36] health outcomes. A possible explanation for the detrimental effects of premorbid disability on later health might be that elevated levels of vulnerability in previously impaired individuals interfere with the general recovery process. Unlike Ramchand et al.,[17] our results did not indicate a continuous reciprocal relationship between PTSD and disability over time. In contrast to their findings, we found that PTSD drove long-term, but not short-term disability, and 3month disability did not have a significant long-term effect on 12-month PTSD in our study. This difference may be a function of our study including anxiety and depression in our model and controlling for pain. While disability had little impact on mental health, psychopathology, however, drove disability over time. Depression showed a high impact on short-term disability, although its impact on long-term disability was nonsignificant. Our findings replicate the results reported by Thombs et al.[14] regarding short-term depression. Also consistent with our results, Kosloski et al.[37] found no significant effect of depression on long-term
self-reported health. One possible explanation for the detrimental effect of depression on short-term, but not long-term physical health may be impaired adherence to medical treatment and self-care in the early phase after injury.[38] Depression severity and adherence to medical treatment are associated in a gradient fashion, with more severe depression symptoms causing poorer adherence early on.[39] High levels of depression may have therefore slowed down the physical recovery process. Unlike depression, anxiety did not have an independent significant effect on disability or mental health. Given that the HADS anxiety measure targets general anxiety symptoms, such as worry and panic,[22, 40] this result may not be surprising, as the link between generalized anxiety disorder and disability has been found to be relatively weak.[41] A possible explanation for the differing relationship between general anxiety and disability, as opposed to PTSD and disability, might be a variation in underlying complex psychobiology patterns (see [42] ) Posttraumatic stress disorder symptoms played a unique role in the aftermath of injury as this was the only mental health variable that contributed to longterm disability. Additionally, PTSD had a unique impact on general mental health, as indicated by its influence on depression and anxiety symptoms over time. In accordance with our results, PTSD was found to be significantly related to a variety of short- and longterm physical and mental health outcomes in a number of studies.[43–45] There is something uniquely damaging about high levels of PTSD symptoms in the aftermath of injury.
TABLE 3. Correlations between psychiatric disorders and disability within waves Time 3 months
Baseline
12 months
Variable
PTSD
Dep
Anx
PTSD
Dep
Anx
PTSD
Dep
Anx
Dep Anx Dis
.49** .62**
.77**
-
.43** .54** .38**
.71** .57**
.41**
.61** .56** .46**
.84** .74**
.61**
Note: Correlations between mental health variables and disability were calculated for the 3- and 12-month follow-up assessments only. PTSD, post-traumatic stress disorder; Dep, major depression; Anx, anxiety; Dis, disability. ∗∗ P < .001. Depression and Anxiety
Research Article: Mental Health and Disability after Injury
Previous research has shown that, compared to other psychiatric disorders, PTSD carries a particularly high level of disability that results in increased health care costs in affected populations.[46] There are several possible explanations for this relationship. First, the avoidance behavior patterns characteristic of PTSD present one possible mechanism.[47] Avoidance of reminders of the traumatic event may prevent the individual from reengaging in their preinjury life, which in turn increases disability levels. There is evidence to suggest avoidance associated with PTSD increases over time[48] that may explain the impact on long-term disability of PTSD in our study. Second, ongoing levels of elevated arousal are known to put individuals at risk for sensitization (see [49] ) that is defined as “an increase in response to a stimulus as a function of repeated representations of that stimulus” ([49] , p.106). Sensitization has been proposed as a mechanism by which PTSD symptoms escalate over time that in turn contributes to higher levels of disability. Furthermore, similar processes have been forwarded to explain the relationship between PTSD and pain, which also may contribute disability over time.[16, 50] Our findings have several implications for future research and treatment of injury populations. The results provide further evidence of the need for early intervention with individuals reporting symptoms of PTSD and depression after injury to prevent long-term physical and mental disability. Although this claim has been made before, efforts to put these recommendations into practice are rare (see [5] ), and have yet failed to show consistent improvement through early treatment (see [51] ). Early intervention using cognitive-behavioral therapy (CBT) has shown promising results in previous research (e.g. [52] ). In a study published by Zatzick et al.,[53] stepped early intervention patients reported significantly reduced PTSD symptoms, and significantly improved physical functioning compared to the usual care condition. Future research should identify programs that can be implemented as routine treatment for individuals scoring high on PTSD and depression symptoms prior to discharge. Such programs would aim to effectively address patients’ needs after injury, improve mental health recovery trajectories, and prevent chronic disability. As a precursor to intervention, effective screening methods are needed to identify individuals that are likely to develop ongoing mental health issues following injury. There have been a number of screens developed in this population that identify those at risk for developing mental health disorders (e.g. [54] ) and evidence that early intervention can prevent and treat early presentations of psychiatric disorder after injury (e.g. [52] ). Given that the majority of individuals with PTSD and other psychiatric disorder do not seek mental health treatment,[55] early screening is crucial to prevent chronic disability. This study has certain limitations. Our sample consisted predominantly of male injury survivors (74%), reducing the generalizability of our results to female injury or other trauma populations. Furthermore, depression, anxiety, and disability were assessed via self-administered
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questionnaires rather than structured clinical interview. Similarly, disability was assessed via self-report and the study may have benefited from the use of an objective measure, such as return to work. Self-report questionnaires are frequently used in psychological research, and have several advantages, but may also be at risk of bias.[43] Finally, the model tested was not a complete model of the factors that contribute to disability after injury. Indeed, our model only accounted for 55% of the variance in long-term disability. It is well known that many variables contribute to disability directly or indirectly such as a past psychiatric history, prior trauma history, compensation status, and social support. While our model did control some variables that we identified as theoretically important to our question, we were unable to include all contributors to disability in the model. Readers need to therefore view our findings with this understanding. Despite these limitations, our findings provide further important insights into the complex relationship between disability and mental health. High levels of early psychopathology resulted in worse than expected recovery after injury over the entire 12-month period, while the impact of disability on mental health was limited to the direct aftermath of injury. PTSD was found to uniquely drive long-term disability, providing additional evidence for the importance of targeting PTSD symptoms as early as possible in injured populations. Given the frequency with which injury occurs, it is important to understand the complex mechanisms underlying the recovery process. Early screening and intervention programs should be adopted routinely for injury victims, focusing on PTSD as well as depression symptoms. The current results have the potential to enhance primary care interventions and the prevention of ongoing chronic disability in exposed individuals. Acknowledgments. The authors gratefully acknowledge all the participants involved in this study. This study was supported by a National Health and Medical Research Council Program Grant (568970). Conflict of interest. The authors have no conflicts of interest to report.
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