Psychology & Health
ISSN: 0887-0446 (Print) 1476-8321 (Online) Journal homepage: http://www.tandfonline.com/loi/gpsh20
Trauma history as a resilience factor for patients recovering from total knee replacement surgery Julie K. Cremeans-Smith, Kenneth Greene & Douglas L. Delahanty To cite this article: Julie K. Cremeans-Smith, Kenneth Greene & Douglas L. Delahanty (2015) Trauma history as a resilience factor for patients recovering from total knee replacement surgery, Psychology & Health, 30:9, 1005-1016, DOI: 10.1080/08870446.2014.1001391 To link to this article: http://dx.doi.org/10.1080/08870446.2014.1001391
Accepted author version posted online: 23 Dec 2014. Published online: 27 Jan 2015. Submit your article to this journal
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=gpsh20 Download by: [University of Nebraska, Lincoln]
Date: 06 November 2015, At: 01:41
Psychology & Health, 2015 Vol. 30, No. 9, 1005–1016, http://dx.doi.org/10.1080/08870446.2014.1001391
Trauma history as a resilience factor for patients recovering from total knee replacement surgery Julie K. Cremeans-Smitha*, Kenneth Greeneb and Douglas L. Delahantyc,d
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
a
Department of Psychology, Kent State University at Stark, N Canton, OH, USA; bDepartment of Orthopedics, Cleveland Clinic, Cleveland, OH, USA; cDepartment of Psychology, Kent State University, Kent, OH, USA; dDepartment of Psychology in Psychiatry, Northeast Ohio Medical University (NEOMED), Rootstown, OH, USA (Received 28 July 2014; accepted 14 December 2014) Research concerning the impact of trauma history on individuals’ ability to cope with subsequent events is mixed. While many studies find that trauma history increases vulnerability for conditions such as post-traumatic stress disorder and chronic pain, others reveal that there are benefits associated with moderate levels of stress (e.g. development of coping skills). Objective: The present study investigated whether the experience of prior traumatic stressors would serve as a risk or resilience factor based on physical and emotional outcomes among patients recovering from total knee replacement surgery (TKR). Design: 110 patients undergoing unilateral, TKR completed surveys before surgery, as well as one and three months following the procedure. Results: Contrary to hypotheses, patients who reported more prior traumas experienced less severe pain and functional limitations at one- (β = −.259, p = .006) and three-month follow-up assessments (β = −.187, p = .04). A similar pattern emerged when specific types of traumas (e.g. interpersonal) were examined in relation to physical recovery. Further, patients’ trauma history was negatively related to symptoms of post-traumatic stress three-months following surgery (e.g. Avoidance: β = −.200, p = .037). Conclusion: Trauma history represents a source of resilience, rather than vulnerability, within the context of arthroplastic surgery. Keywords: post-traumatic stress; arthroplasty; post-operative recovery; trauma history; resilience
When confronted by a life stressor, one’s coping resources may be overwhelmed by this latest addition to allostatic load or one may draw upon past experiences as a source of strength. As such, the experience of prior traumatic events may function as a risk or a resilience factor, impacting how one responds to future life events. Among patients coping with painful conditions, prior traumatic experiences are associated with greater physical and mental suffering (e.g. Linton, 2002; Walker et al., 1997). However, the resilience literature has argued that prior life events facilitate the development of coping resources, potentially enhancing one’s ability to manage future stressors (for review, see Aldwin, 2007). Arthroplastic surgery is a significant source of stress, following which *Corresponding author. Email: [email protected] © 2015 Taylor & Francis
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
1006
J.K. Cremeans-Smith et al.
many patients experience severe pain (FitzGerald et al., 2004) and emotional distress (Cremeans-Smith, Greene, & Delahanty, 2011). The current study examines whether patients’ experience of prior traumatic events serves as a risk or resilience factor in the aftermath of total knee replacement surgery (TKR). Prior research suggests that a lifetime history of traumatic events may increase one’s vulnerability to post-traumatic stress disorder (PTSD) following a later event. For example, exposure to prior traumatic events has been found to increase the likelihood of PTSD following a variety of stressors, including motor vehicle accident (Irish et al., 2008), assault (i.e. physical and/or sexual; Cougle, Resnick, & Kilpatrick, 2009), rape (Yehuda, Resnick, Schmeidler, Yang, & Pitman, 1998) and combat (Clancy et al., 2006; King, King, Foy, & Gudanowski, 1996; Zaidi & Foy, 1994), among others. However, findings are mixed as to whether prior traumatic experiences must be similar to the index event to confer vulnerability for subsequent PTSD. For example, Resnick, Yehuda, Pitman, and Foy (1995) found that women who had experienced at least one prior sexual assault were more likely to develop PTSD in the aftermath of a recent sexual assault. However, others have suggested that the experience of previous, dissimilar stressors increases the likelihood of developing psychopathology following a recent trauma (e.g. Andrykowski & Cordova, 1998; Clancy et al., 2006; Dougall, Herberman, Delahanty, Inslich, & Baum, 2000; Peretz, Baider, Ever-Hadani, & De-Nour, 1994). The experience of traumatic events is thought to foster the development of physiological and psychological vulnerability, which increases the likelihood of PTSD in the aftermath of some future event. For example, anxiety sensitivity and dissociation, two markers of psychological risk for later PTSD, occur more frequently among individuals with a history of traumatic experiences compared to non-traumatized controls (e.g. Kamen, Bergstrom, Koopman, Lee, & Gore-Felton, 2012; Lang, Kennedy, & Stein, 2002). While much of the literature on PTSD supports trauma history as a vulnerability factor, there are exceptions which suggest that prior life events may inoculate individuals against distress in the aftermath of trauma (e.g. Norris & Murrell, 1988). A significant proportion of individuals with painful conditions have experienced traumatic life events. For instance, Walker et al. (1997) found that 91.7% of individuals with fibromyalgia report having experienced at least one instance of sexual or physical assault during their lifetime. Further, individuals with a history of abuse are more likely to report abdominal pain than non-abused individuals (for review, see Leserman & Drossman, 2007). Even among a pain-free sample of the general population, individuals who report a history of physical or sexual abuse are more likely to develop pain and decline in physical functioning over the course of a one-year follow-up (Linton, 2002). Therefore, trauma history may serve as a vulnerability factor for physical pain as well as emotional distress. The present study The purpose of the present study is to examine whether prior traumatic events serve as a risk or resilience factor following arthroplastic surgery. In accordance with The Shared Vulnerability Model (Asmundson, Coons, Taylor, & Katz, 2002) which suggests that common psychological and physiological processes predispose individuals to the development of PTSD and pain following exposure to stressful stimuli, we expected trauma history to function as a risk factor in the present study. Specifically, we hypothesised
Psychology & Health
1007
that patients who reported more prior traumatic stressors would experience a more difficult post-operative recovery, characterised by severe pain, functional limitations and symptoms of post-traumatic stress.
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
Methods Participants Participants consisted of 123 consecutive unilateral, TKR patients recruited through the Department of Orthopedics at Summa Health System (Akron, Ohio). Of the 123 patients who agreed to participate in the study, six dropped out for health-related reasons (e.g. development of other conditions prior to surgery and hospitalisation for other medical conditions), five decided they were no longer interested in participating and two patients postponed their surgeries. Therefore, the final sample consisted of 110 patients, the majority of whom were female (68%; 32% male), Caucasian (93; 7% African American), and undergoing TKR for the first time (75.5; 24.5% previous TKR on the other knee). Patients ranged in age from 49 to 90 years (M = 69.20). Details regarding recruitment of patients have been previously reported (Cremeans-Smith, Millington, Sledjeski, Greene, & Delahanty, 2006). Procedures The following procedures were approved by the Institutional Review Boards of Kent State University and Summa Health System. At three time points, researchers delivered questionnaires to participants’ homes: 2–3 weeks prior to surgery (time 1:T1), one month following surgery (time 2:T2) and three months following surgery (time 3:T3). At each of these times, patients were requested to complete the questionnaires within the next 72 h. Participants received $25 to reimburse them for their time and effort in completing each assessment time point. Measures Trauma history Participants’ lifetime exposure to traumatic stress was assessed using a modified version of the Traumatic Stress Schedule (Norris, 1990). Participants were asked to indicate their exposure to nine traumatic events and to report in an open-ended format any additional experiences that they felt were traumatic (completed at T3). For each endorsed event, participants were asked to indicate the number of times the event occurred, as well as the extent to which they feared for their life, were physically injured, and were distressed by the event (Irish et al., 2008). Number of traumas experienced was calculated by summing the total number of prior events reported by each participant (i.e. number of items endorsed × number of occurrences). Knee-specific pain and functionality To assess knee pain and functionality before and after TKR, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; Bellamy, Buchanan, Goldsmith, Campbell, & Stitt, 1988) was administered at T1, T2 and T3. The WOMAC is a general
1008
J.K. Cremeans-Smith et al.
measure of functionality that assesses limitations, stiffness and pain in the knee associated with tasks of daily living (e.g. ascending/descending stairs, putting on socks, getting in and out of a car, etc.) The WOMAC asks individuals to rate the severity of their difficulty/pain with completing tasks that involve knee movement on a five-point Likert scale from 0 (none) to 4 (extreme). Greater values on the WOMAC indicate more severe limitations, stiffness and pain (Cronbach’s alpha at T1 = 0.946, T2 = 0.950 and T3 = 0.946).
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
Symptoms of post-traumatic stress Patients completed the Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) at T2 and T3. Patients were instructed to think about their surgery as they completed the IES. Although the IES does not allow for diagnostic determinations, research has suggested that a total IES score of 19 provides a sensitivity of 0.93 and a specificity of 0.84 for identifying individuals who meet diagnostic criteria for PTSD (Wohlfarth, van der Brink, Winkel, & ter Smitten, 2003). Greater values on the IES indicate more symptoms of post-traumatic stress (Cronbach’s alpha at T2 = 0.891 and T3 = 0.896). The IES also provides subscales for symptoms of avoidance and intrusive thoughts (Cronbach’s alpha for Avoidance: T2 = 0.789, T3 = 0.805; Intrusive thoughts: T2 = 0.811, T3 = 0.819). Depressive symptoms Given the established relationships between depression, pain and PTSD (e.g. Blanchard et al., 2004; Brady, Killeen, Brewerton, & Lucerini, 2000; Keane & Wolfe, 1990; Williams, Jacka, Pasco, Dodd, & Berk, 2006), baseline depressive symptoms (T1) were included as a covariate in the regression models. Depressive symptoms were assessed using the Center for Epidemiological Studies-Depression Scale (CES-D; Radloff, 1977). The CES-D is a 20-item questionnaire for assessing depressive symptoms experienced during the week prior to the assessment. The CES-D asks individuals to rate the frequency of their depressive symptoms on a four-point Likert scale from 0 (never) to 3 (most of the time). Items were summed to yield a total depression score (Cronbach’s alpha = 0.841). Results Descriptive statistics and bivariate correlations between study variables are displayed in Tables 1 and 2, respectively. Using up to four predictors (one independent variable and up to three control variables), a power analysis (GPower 3; Faul, Erdfelder, Lang, & Buchner, 2007) indicated a necessary minimum sample size of 80 to provide adequate power (.95) to detect moderate effect sizes (.25) in the final model, indicating that the study was adequately powered. On average, patients reported having experienced few traumatic events during their lifetime (Mean = 2.20). However, there was considerable variability among individuals, as illustrated by the range of responses (0–27 events, see Table 1). Traumatic events most frequently reported by the current sample included witnessing someone die (32/ 110; 29.1%) or involvement in a motor vehicle accident (24/110; 21.8%).
Psychology & Health
1009
Table 1. Descriptive statistics for study variables. Mean
SD
Range
Total prior traumas Interpersonal traumas Injurious traumas
2.20 0.53 1.06
4.29 2.40 2.94
0–27 0–21 0–25
Prior to surgery One-month follow-up Three-month follow-up
34.81 28.83 19.59
11.86 11.85 10.28
3–63 3–63 0–43
12.30 5.61 6.76
13.00 7.05 6.66
0–56 0–28 0–30
11.43 6.07 5.36
13.00 7.79 6.36
0–55 0–28 0–30
TSS
WOMAC
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
IES One-month follow-up Total score Avoidance Intrusive thoughts Three-month follow-up Total score Avoidance Intrusive thoughts
TSS: Traumatic Stress Schedule, WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index, IES: Impact of Event Scale.
Table 2. Correlations between study variables. 1 1. 2. 3. 4. 5. 6. 7.
Total prior traumas Interpersonal traumas Injurious traumas WOMAC one-month follow-up WOMAC three-month follow-up IES one-month follow-up IES three-month follow-up
– – – – – – –
2 .803 – – – – – –
3 **
4 **
.803 .952** – – – – –
−.196 −.170 −.164 – – – –
*
5
6
7
−.172 −.127 −.148 .527** – – –
−.032 .034 .069 .367** .366** – –
−.117 −.060 −.066 .028* .399** .625** –
WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index, IES: Impact of Event Scale. *p < .05; **p < .01.
Control variables for regression models were selected on the basis of an examination of bivariate correlations and t tests between a set of background variables (i.e. age, gender, educational attainment, household income, race and previous knee surgery) and post-operative recovery. Variables with significant bivariate correlations or t tests (p
ISSN: 0887-0446 (Print) 1476-8321 (Online) Journal homepage: http://www.tandfonline.com/loi/gpsh20
Trauma history as a resilience factor for patients recovering from total knee replacement surgery Julie K. Cremeans-Smith, Kenneth Greene & Douglas L. Delahanty To cite this article: Julie K. Cremeans-Smith, Kenneth Greene & Douglas L. Delahanty (2015) Trauma history as a resilience factor for patients recovering from total knee replacement surgery, Psychology & Health, 30:9, 1005-1016, DOI: 10.1080/08870446.2014.1001391 To link to this article: http://dx.doi.org/10.1080/08870446.2014.1001391
Accepted author version posted online: 23 Dec 2014. Published online: 27 Jan 2015. Submit your article to this journal
Article views: 133
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=gpsh20 Download by: [University of Nebraska, Lincoln]
Date: 06 November 2015, At: 01:41
Psychology & Health, 2015 Vol. 30, No. 9, 1005–1016, http://dx.doi.org/10.1080/08870446.2014.1001391
Trauma history as a resilience factor for patients recovering from total knee replacement surgery Julie K. Cremeans-Smitha*, Kenneth Greeneb and Douglas L. Delahantyc,d
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
a
Department of Psychology, Kent State University at Stark, N Canton, OH, USA; bDepartment of Orthopedics, Cleveland Clinic, Cleveland, OH, USA; cDepartment of Psychology, Kent State University, Kent, OH, USA; dDepartment of Psychology in Psychiatry, Northeast Ohio Medical University (NEOMED), Rootstown, OH, USA (Received 28 July 2014; accepted 14 December 2014) Research concerning the impact of trauma history on individuals’ ability to cope with subsequent events is mixed. While many studies find that trauma history increases vulnerability for conditions such as post-traumatic stress disorder and chronic pain, others reveal that there are benefits associated with moderate levels of stress (e.g. development of coping skills). Objective: The present study investigated whether the experience of prior traumatic stressors would serve as a risk or resilience factor based on physical and emotional outcomes among patients recovering from total knee replacement surgery (TKR). Design: 110 patients undergoing unilateral, TKR completed surveys before surgery, as well as one and three months following the procedure. Results: Contrary to hypotheses, patients who reported more prior traumas experienced less severe pain and functional limitations at one- (β = −.259, p = .006) and three-month follow-up assessments (β = −.187, p = .04). A similar pattern emerged when specific types of traumas (e.g. interpersonal) were examined in relation to physical recovery. Further, patients’ trauma history was negatively related to symptoms of post-traumatic stress three-months following surgery (e.g. Avoidance: β = −.200, p = .037). Conclusion: Trauma history represents a source of resilience, rather than vulnerability, within the context of arthroplastic surgery. Keywords: post-traumatic stress; arthroplasty; post-operative recovery; trauma history; resilience
When confronted by a life stressor, one’s coping resources may be overwhelmed by this latest addition to allostatic load or one may draw upon past experiences as a source of strength. As such, the experience of prior traumatic events may function as a risk or a resilience factor, impacting how one responds to future life events. Among patients coping with painful conditions, prior traumatic experiences are associated with greater physical and mental suffering (e.g. Linton, 2002; Walker et al., 1997). However, the resilience literature has argued that prior life events facilitate the development of coping resources, potentially enhancing one’s ability to manage future stressors (for review, see Aldwin, 2007). Arthroplastic surgery is a significant source of stress, following which *Corresponding author. Email: [email protected] © 2015 Taylor & Francis
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
1006
J.K. Cremeans-Smith et al.
many patients experience severe pain (FitzGerald et al., 2004) and emotional distress (Cremeans-Smith, Greene, & Delahanty, 2011). The current study examines whether patients’ experience of prior traumatic events serves as a risk or resilience factor in the aftermath of total knee replacement surgery (TKR). Prior research suggests that a lifetime history of traumatic events may increase one’s vulnerability to post-traumatic stress disorder (PTSD) following a later event. For example, exposure to prior traumatic events has been found to increase the likelihood of PTSD following a variety of stressors, including motor vehicle accident (Irish et al., 2008), assault (i.e. physical and/or sexual; Cougle, Resnick, & Kilpatrick, 2009), rape (Yehuda, Resnick, Schmeidler, Yang, & Pitman, 1998) and combat (Clancy et al., 2006; King, King, Foy, & Gudanowski, 1996; Zaidi & Foy, 1994), among others. However, findings are mixed as to whether prior traumatic experiences must be similar to the index event to confer vulnerability for subsequent PTSD. For example, Resnick, Yehuda, Pitman, and Foy (1995) found that women who had experienced at least one prior sexual assault were more likely to develop PTSD in the aftermath of a recent sexual assault. However, others have suggested that the experience of previous, dissimilar stressors increases the likelihood of developing psychopathology following a recent trauma (e.g. Andrykowski & Cordova, 1998; Clancy et al., 2006; Dougall, Herberman, Delahanty, Inslich, & Baum, 2000; Peretz, Baider, Ever-Hadani, & De-Nour, 1994). The experience of traumatic events is thought to foster the development of physiological and psychological vulnerability, which increases the likelihood of PTSD in the aftermath of some future event. For example, anxiety sensitivity and dissociation, two markers of psychological risk for later PTSD, occur more frequently among individuals with a history of traumatic experiences compared to non-traumatized controls (e.g. Kamen, Bergstrom, Koopman, Lee, & Gore-Felton, 2012; Lang, Kennedy, & Stein, 2002). While much of the literature on PTSD supports trauma history as a vulnerability factor, there are exceptions which suggest that prior life events may inoculate individuals against distress in the aftermath of trauma (e.g. Norris & Murrell, 1988). A significant proportion of individuals with painful conditions have experienced traumatic life events. For instance, Walker et al. (1997) found that 91.7% of individuals with fibromyalgia report having experienced at least one instance of sexual or physical assault during their lifetime. Further, individuals with a history of abuse are more likely to report abdominal pain than non-abused individuals (for review, see Leserman & Drossman, 2007). Even among a pain-free sample of the general population, individuals who report a history of physical or sexual abuse are more likely to develop pain and decline in physical functioning over the course of a one-year follow-up (Linton, 2002). Therefore, trauma history may serve as a vulnerability factor for physical pain as well as emotional distress. The present study The purpose of the present study is to examine whether prior traumatic events serve as a risk or resilience factor following arthroplastic surgery. In accordance with The Shared Vulnerability Model (Asmundson, Coons, Taylor, & Katz, 2002) which suggests that common psychological and physiological processes predispose individuals to the development of PTSD and pain following exposure to stressful stimuli, we expected trauma history to function as a risk factor in the present study. Specifically, we hypothesised
Psychology & Health
1007
that patients who reported more prior traumatic stressors would experience a more difficult post-operative recovery, characterised by severe pain, functional limitations and symptoms of post-traumatic stress.
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
Methods Participants Participants consisted of 123 consecutive unilateral, TKR patients recruited through the Department of Orthopedics at Summa Health System (Akron, Ohio). Of the 123 patients who agreed to participate in the study, six dropped out for health-related reasons (e.g. development of other conditions prior to surgery and hospitalisation for other medical conditions), five decided they were no longer interested in participating and two patients postponed their surgeries. Therefore, the final sample consisted of 110 patients, the majority of whom were female (68%; 32% male), Caucasian (93; 7% African American), and undergoing TKR for the first time (75.5; 24.5% previous TKR on the other knee). Patients ranged in age from 49 to 90 years (M = 69.20). Details regarding recruitment of patients have been previously reported (Cremeans-Smith, Millington, Sledjeski, Greene, & Delahanty, 2006). Procedures The following procedures were approved by the Institutional Review Boards of Kent State University and Summa Health System. At three time points, researchers delivered questionnaires to participants’ homes: 2–3 weeks prior to surgery (time 1:T1), one month following surgery (time 2:T2) and three months following surgery (time 3:T3). At each of these times, patients were requested to complete the questionnaires within the next 72 h. Participants received $25 to reimburse them for their time and effort in completing each assessment time point. Measures Trauma history Participants’ lifetime exposure to traumatic stress was assessed using a modified version of the Traumatic Stress Schedule (Norris, 1990). Participants were asked to indicate their exposure to nine traumatic events and to report in an open-ended format any additional experiences that they felt were traumatic (completed at T3). For each endorsed event, participants were asked to indicate the number of times the event occurred, as well as the extent to which they feared for their life, were physically injured, and were distressed by the event (Irish et al., 2008). Number of traumas experienced was calculated by summing the total number of prior events reported by each participant (i.e. number of items endorsed × number of occurrences). Knee-specific pain and functionality To assess knee pain and functionality before and after TKR, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC; Bellamy, Buchanan, Goldsmith, Campbell, & Stitt, 1988) was administered at T1, T2 and T3. The WOMAC is a general
1008
J.K. Cremeans-Smith et al.
measure of functionality that assesses limitations, stiffness and pain in the knee associated with tasks of daily living (e.g. ascending/descending stairs, putting on socks, getting in and out of a car, etc.) The WOMAC asks individuals to rate the severity of their difficulty/pain with completing tasks that involve knee movement on a five-point Likert scale from 0 (none) to 4 (extreme). Greater values on the WOMAC indicate more severe limitations, stiffness and pain (Cronbach’s alpha at T1 = 0.946, T2 = 0.950 and T3 = 0.946).
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
Symptoms of post-traumatic stress Patients completed the Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) at T2 and T3. Patients were instructed to think about their surgery as they completed the IES. Although the IES does not allow for diagnostic determinations, research has suggested that a total IES score of 19 provides a sensitivity of 0.93 and a specificity of 0.84 for identifying individuals who meet diagnostic criteria for PTSD (Wohlfarth, van der Brink, Winkel, & ter Smitten, 2003). Greater values on the IES indicate more symptoms of post-traumatic stress (Cronbach’s alpha at T2 = 0.891 and T3 = 0.896). The IES also provides subscales for symptoms of avoidance and intrusive thoughts (Cronbach’s alpha for Avoidance: T2 = 0.789, T3 = 0.805; Intrusive thoughts: T2 = 0.811, T3 = 0.819). Depressive symptoms Given the established relationships between depression, pain and PTSD (e.g. Blanchard et al., 2004; Brady, Killeen, Brewerton, & Lucerini, 2000; Keane & Wolfe, 1990; Williams, Jacka, Pasco, Dodd, & Berk, 2006), baseline depressive symptoms (T1) were included as a covariate in the regression models. Depressive symptoms were assessed using the Center for Epidemiological Studies-Depression Scale (CES-D; Radloff, 1977). The CES-D is a 20-item questionnaire for assessing depressive symptoms experienced during the week prior to the assessment. The CES-D asks individuals to rate the frequency of their depressive symptoms on a four-point Likert scale from 0 (never) to 3 (most of the time). Items were summed to yield a total depression score (Cronbach’s alpha = 0.841). Results Descriptive statistics and bivariate correlations between study variables are displayed in Tables 1 and 2, respectively. Using up to four predictors (one independent variable and up to three control variables), a power analysis (GPower 3; Faul, Erdfelder, Lang, & Buchner, 2007) indicated a necessary minimum sample size of 80 to provide adequate power (.95) to detect moderate effect sizes (.25) in the final model, indicating that the study was adequately powered. On average, patients reported having experienced few traumatic events during their lifetime (Mean = 2.20). However, there was considerable variability among individuals, as illustrated by the range of responses (0–27 events, see Table 1). Traumatic events most frequently reported by the current sample included witnessing someone die (32/ 110; 29.1%) or involvement in a motor vehicle accident (24/110; 21.8%).
Psychology & Health
1009
Table 1. Descriptive statistics for study variables. Mean
SD
Range
Total prior traumas Interpersonal traumas Injurious traumas
2.20 0.53 1.06
4.29 2.40 2.94
0–27 0–21 0–25
Prior to surgery One-month follow-up Three-month follow-up
34.81 28.83 19.59
11.86 11.85 10.28
3–63 3–63 0–43
12.30 5.61 6.76
13.00 7.05 6.66
0–56 0–28 0–30
11.43 6.07 5.36
13.00 7.79 6.36
0–55 0–28 0–30
TSS
WOMAC
Downloaded by [University of Nebraska, Lincoln] at 01:41 06 November 2015
IES One-month follow-up Total score Avoidance Intrusive thoughts Three-month follow-up Total score Avoidance Intrusive thoughts
TSS: Traumatic Stress Schedule, WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index, IES: Impact of Event Scale.
Table 2. Correlations between study variables. 1 1. 2. 3. 4. 5. 6. 7.
Total prior traumas Interpersonal traumas Injurious traumas WOMAC one-month follow-up WOMAC three-month follow-up IES one-month follow-up IES three-month follow-up
– – – – – – –
2 .803 – – – – – –
3 **
4 **
.803 .952** – – – – –
−.196 −.170 −.164 – – – –
*
5
6
7
−.172 −.127 −.148 .527** – – –
−.032 .034 .069 .367** .366** – –
−.117 −.060 −.066 .028* .399** .625** –
WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index, IES: Impact of Event Scale. *p < .05; **p < .01.
Control variables for regression models were selected on the basis of an examination of bivariate correlations and t tests between a set of background variables (i.e. age, gender, educational attainment, household income, race and previous knee surgery) and post-operative recovery. Variables with significant bivariate correlations or t tests (p
