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The Impact of Event Scale – Revised: psychometric properties of the Lithuanian version in a sample of employees exposed to workplace bullying

Background. The Impact of Event Scale-Revised (IES-R) is often used as a self-report instrument for symptoms of post-traumatic stress (PTS). The objective of this study was to explore the reliability and validity of the Lithuanian IES-R in a sample of employees with exposure to workplace bullying in different occupations. Materials and methods. The original IES-R was translated into Lithuanian, and the comparability of content was verified through back-translation procedures. 294 employees with exposure to workplace bullying (52 teachers from the secondary schools of Kaunas, 56 family physicians, 101 nurses of internal medicine departments, 40 waiters, and 45 seafarers) were administered the Lithuanian IES-R and the General Health Questionnaire – 12 (GHQ-12) in order to verify some aspects of convergent validity. The exploratory factor analysis was used to verify the construct validity of the IES-R. Results. The reliability of the Lithuanian version of the IES-R was verified. Cronbach’s α of the total scale was 0.95. Exploratory factor analysis showed a clear factor structure with three independent dimensions: intrusion, avoidance and hyperarousal. Cronbach’s α for subscales of intrusion, avoidance and hyperarousal were 0.89, 0.85, and 0.88, respectively. The convergent validity was supported by positive correlations between the subscales (intrusion, avoidance, hyperarousal) and the GHQ-12. Conclusions. The results suggest that the self-reported Lithuanian IES-R is a valid instrument for assessing the dimensions of post-traumatic stress, has good psychometric properties, and may be applied in prolonged trauma-exposed populations.


INTRODUCTION
In 1980, post-traumatic stress disorder (PTSD) was introduced into the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III), and later also into the fourth edition (DSM-IV). On the basis of the diagnostic criteria of the DSM-IV, PTSD is an anxiety disorder that follows a traumatic event (Criterion A). It is characterized by recurrent re-experiencing of the traumatic event (Criterion B), constant avoidance of trauma-related stimuli and emotional numbing (Criterion C), and persistent symptoms of hyperarousal (Criterion D). In addition, symptoms must be prevalent for at least one month (Criterion E) and lead to impaired functioning in at least one important life domain (Criterion F) (1). In DSM-V Criterion A (exposure to a traumatic event) was additionally defined as "individual experiences first-hand repeated or extreme exposure to aversive details of the traumatic event" (2). A prolonged stress reaction, e. g., produced by ongoing exposure to workplace bullying, has been found to be particularly detrimental to the victim's health and causes significant psychological stress in those exposed, possibly leading to a range of post-traumatic stress symptoms (PTSS) (3). One of the most widely used self-report instruments for the assessment of PTSS is the Impact of Event Scale Revised (IES-R). It was developed to cover all three clusters of symptoms of PTSD (i. e., intrusion, avoidance and hyperarousal) with respect to a particular life-threatening event (4). It consists of 22 items. It was translated and adapted in many languages for the detection of PTSS after tsunamis, earthquakes, floods, attacks, etc. (5)(6)(7)(8)(9)(10)(11), and showed good psychometric properties. In Lithuania, the psychometric properties of the IES-R were tested in a sample of 475 persons with traumatic experiences evaluated by the Harvard Trauma questionnaire (12). The studies investigating the associations between workplace bullying and PTSS are scarce, though good psychometric properties of the IES-R were demonstrated in the investigation of the relationship between exposure to workplace bullying and symptoms of posttraumatic stress in a cross-sectional sample of 221 self-labelled targets of workplace bullying (13) and family physicians (14).
The objective of the present paper was to validate the Lithuanian version of the IES-R in a large sample of victims of workplace bullying in five ifferent occupations in Lithuania.

Participants and procedure
This cross-sectional study was approved by Kaunas Regional Biomedical Research Ethics Committee (No. BE-2-12) and was carried out from 2013 to 2015 in representative samples of employees from Kaunas representing five occupations -teachers, family physicians, internal medicine department nurses, waiters, and seafarers. In total, 1378 employees were investigated.
The sample consisted of: -406 teachers from 13 secondary education schools (response rate 71.3%). The mean age of the participants was 49.92 years (standard deviation (SD): 9.11). 81.0% were females and 7.9% were males.
-173 family physicians from five public and five private out-patient clinics (response rate 65.7%). The mean age of the participants was 52.46 years (SD): 9.00). 82.8% were females and 17.2% were males.
-311 internal medicine department nurses from three hospitals (response rate 69.1%). The mean age of the participants was 46.65 years (SD): 8.98). 99.7% were females and 0.3% was males.
-147 waiters from 217 cafes (response rate 72.1% Those participants with workplace bullying experience were administered the IES-R, and the psychometric properties of the Lithuanian IES-R are presented in this article.

Measures
Participants completed an anonymous self-administered questionnaire which included sociodemographic measures and questionnaires to measure workplace bullying, PTSS, and psychological distress.
The Negative Acts Questionnaire (H. Hoel & S. Einar sen) was used to assess the variety of negative behaviour forms, and victimization from workplace bullying was measured using the single-item measure. The respondents were asked to indicate if they had experienced bullying during the last six months. Bullying was then classified into two categories -occasional and severe (weekly and more frequent) (15). This report presents data on the victims of occasional and severe bullying.
Due to experienced workplace bullying, posttraumatic stress symptoms were assessed by the Impact of Event Scale-Revised (IES-R) inventory (4). The IES-R is a short, easily administered self-report questionnaire containing 22 items. Each item is rated on a 5-point scale using anchors between 0 (not at all) and 4 (extremely), reflecting the extent to which a particular symptom was a problem for the respondent during the past week in relation to workplace bullying. The items that compose the scale include: 8 for intrusion symptoms, 8 for avoidance and numbing symptoms, and 6 for arousal symptoms. The maximum score is 88, which would indicate the worst PTSS state. Psychometric properties of the scale were tested in numerous studies (5)(6)(7)(8)(9)(10)(11)(12). Scoring over 33 was considered as a cut off for a "probable PTSD case" (16).
The comparability of the Lithuanian IES-R and the original IES-R has been validated by stringent back-translation procedures. First, the IES-R was translated into Lithuanian by two psychiatrists and one psychologist, and any English phrases that were difficult to understand were translated into Lithuanian after consulting a Lithuanian professor of English literature. Then, the Lithuanian IES-R was back-translated by a person bilingual in English and Lithuanian to validate the trans-lation, and the back-translated version was reviewed. As a result, some items such as 5, 13, and 17 in the first Lithuanian version were modified to better correspond to the meaning of the original items in the IES-R. The content of the final Lithuanian IES-R was further verified by a back-translation procedure until the meaning of each item matched the original item of the IES-R. After obtaining permission from the original author of the translated version, we established the final Lithuanian IES-R.
Psychological distress was measured by Goldberg's 12-item General Health Questionnaire (GHQ-12), which is a well-established self-administered screening scale for the evaluation of psychological distress in non-clinical population samples, valued for its excellent screening performances and good clinical validity in terms of diagnosing mental disorders and measuring general psychological well-being (17) and used in studies in the primary care sector (18). The short GHQ version consists of 12 questions covering feelings of strain, anxiety-based insomnia, depression, inability to cope, lack of self-confidence, and other symptoms of psychological distress. The reliability and validity of the Lithuanian version of the GHQ-12 were verified in local studies (19). Three and more positive answers were assessed as psychological distress. The Lithuanian version of the GHQ-12 was used to examine the external validity of the Lithuanian IES-R. Internal consistency of the GHQ-12 in the present study was calculated using Cronbach's α coefficients. It was 0.81 for family physicians, 0.83 for nurses, 0.75 for teachers, 0.68 for seafarers, and 0.79 for waiters. Cronbach's α for the whole sample was 0.80.

Data analyses
The SPSS version 20.0 was used for data entry and analysis. In order to investigate the underlying dimensional structure of the scale, exploratory principal axis factor analyses with equamax rotation were performed on the whole sample. Prior to exploratory factor analysis, Bartlett's test of sphericity was used to inspect data to ensure items were significantly correlated; to ensure they shared sufficient variance to justify factor extraction the Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy was used. Sampling adequacy values that are less than 0.50 are considered unacceptable, values that are between 0.50 and 0.60 are considered marginally acceptable, and values greater than 0.80 and 0.90 are considered excellent (20). Kaiser's criterion was used to set a number of factors. Salience was detected by applying the three following item-retention criteria to the rotated structure matrix: (1) a factor loading of at least 0.30 on the primary factor, ensuring a high degree of association between the item and the factor; (2) a difference of 0.30 between the loading on the primary factor and the loading on other factors; (3) a minimum of three items for each factor, ensuring meaningful interpretation of stable factors (21).
Internal consistencies of the total scale and subscales were calculated using Cronbach's α coefficient. In order to investigate the extent to which factor scores were correlated, we used the Pearson correlation coefficient.

Descriptive statistics
The mean score on the IES-R was 1.23 (SD = 0.73) for the total sample ( Table 1). As recommended by Creamer et al. (16), a "probable PTSS case" was identified by using a cut-off of the total score of 33 on the IES-R. According to this criterion, a total of 88 (29.9%) participants were identified as probable PTSS cases. Of them, 79.6% were women and 20.4% were men.

Exploratory factor analysis
To assess the construct validity of the Lithuanian IES-R, a principal components analysis was performed to all the subjects on the 22 items of the scale. Bartlett's test sphericity (χ 2 = 5,101.951; df = 231) was significant (p < 0.0001), and the KMO measure of sampling adequacy was 0.949, indicating that the constructing questionnaire items were appropriate for factor analysis. The Kaiser-Guttman criterion and the inspection of the scree plot suggested extracting three factors. The factor correlation matrix, indicating a prominent inter-correlation among factor scales, supported the use of the rotation procedures (the equamax criterion). Factor loadings greater than 0.51 were considered significant. Exploratory factor analysis revealed that the Lithuanian IES-R had three underlying factors accounting for 51.6% of the total variance and generated the intrusion factor (items 1, 2, 3, 6, 9, 14, 16, and 20), the avoidance factor (items 5, 7, 8, 11, 12, 13, 17, and 22), and the hyperarousal factor (items 4, 10, 15, 18, 19, and 21) ( Table 2).
Intercorrelations between subscale scores were r = 0.73 (p < 0.01) between hyperarousal and avoidance; r = 0.86 (p < 0.01) between hyperarousal and intrusion; r = 0.76 (p < 0.01) between intrusion and avoidance. As expected, the dimensions showed a significant level of correlation with each other, indicating that the questionnaire subscales measured several approaches of the impact of event.

Convergent validity
To examine the convergent validity of the Lithuanian IES-R as a measure of psychological distress, the relationship with GHQ-12 scores was examined. Pearson correlation between the total score of the GHQ-12 and the whole Lithuanian IES-R was 0.413, p < 0.001. Further, three Lithuanian IES-R subscale scores were studied. The correlation coefficients for the intrusion subscale score (r = 0.416), the avoidance subscale score (r = 0.356), and the hyperarousal subscale score (r = 0.418) were significant (p < 0.01).

DISCUSSION
Workplace bullying, that is, systematic and longterm exposure to aggression and social exclusion by other organisation members is prevalent in contemporary working life (22). Typically, victims of bullying are exposed to an ever harsher treatment by their tormentors over a long period of time and in a situation where they initially, or at least eventually, experience great difficulties de-fending themselves from these ongoing attacks and instances of social exclusion, with the result that they gradually become ever more victimized and stigmatized. Studies have shown that this may go on for months and years and tends to become as something of a continuous shock to those exposed (23), with potentially traumatic effects on those exposed (3). In the beginning of the process, the negative behaviours are often indirect and subtle thus difficult to recognize and confront, and often lead to much confusion and anxiety in those exposed. The next phase tends to involve more direct and openly aggressive acts, often leaving the target humiliated, ridiculed and increasingly isolated (24). Research has shown that the work situation of these victims may become so difficult that finally they either choose to leave work, or they are forced out of the workplace by means of dismissal or redundancy (25). This study examined the factor structure, internal consistency, and concurrent validity of the IES-R in a sample of five occupations in Lithuania investigated in relation to exposure to workplace bullying. Results supported the three-factor structure of the Lithuanian IES-R -Intrusion, Avoidance, and Hyperarousal, with adequate internal consistency noted for each subscale. As with previous accounts (e. g., Creamer et al., 2003), the three subscales of the IES-R showed a high degree of intercorrelation (16). Given that most of extant studies on the factor structure of PTSD were all conducted in the samples from populations exposed to tsunamis, earthquakes, floods, civilian trauma, terrorist attack, or military combat, the current study contributes to the literature by drawing data from an occupational sample exposed to workplace bullying.
The current study results indicate that items 2 and 15 which both discuss sleep disorders were on different factors: hyperarousal and intrusion. This is considered very appropriate because those items are originally derived from the same source in DSM-IV, namely D1 (sleep disturbance) which consist of a double-barreled question ("difficulty falling or staying asleep") (American Psychiatric Association 2000) (1). Weiss & Marmar (1997) modified the original item of sleep disturbance into two items which are: trouble falling asleep and trouble staying asleep (4). It was decided to put these items into different factors due to their high correlation to those factors. Item No. 2, trouble staying asleep, was assigned to the intrusion subscale since it had higher correlation with items on that subscale, while item No. 15, trouble falling asleep, was put into the hyperarousal subscale due to its correlation with the subscale (26). This result is similar to the findings of , who also identified these two items as separate factor structures of sleep (27).
Several limitations in this study should be noted. First, the generalizability of our findings is limited by our utilization of a sample of five specific occupations in Lithuania. These findings need to be further tested with samples drawn from other occupations in Lithuania.
The present study is also limited by the use of a single self-reported screening instrument, the GHQ-12, for examination of the convergent validity of the Lithuanian IES-R. Further investigation of the relationship between the Lithuanian IES-R and other specific measurements of PTSD, such as the Clinician-Administered PTSD Scale (CAPS) (28,29), as well as systematically conducted clinical interviews would be needed to examine the specificity of the Lithuanian IES-R for screening PTSS in future. On the other hand, the comparison of the Lithuanian IES-R with other general measures of psychological distress, such as the Symptom Checklist 90 -Revised (SCL-90-R) (30), would also help to further establish the external validity of the Lithuanian IES-R.
Notwithstanding these limitations, the present study provides empirical support for the adapted Lithuanian version of the IES-R.
In summary, the study extends the available psychometric information to support the efficacy of the IES-R as a tool for assessing the impact of traumatic experience on the victims of workplace bullying. In particular, this study provides support for the translated version of the IES-R for use with Lithuanian participants. Assessing survivors for PTSS and other psychological sequelae resulting from workplace bullying experience is important as it provides mental health specialists with the information needed to make decisions about the development and implementation of appropriate interventions when and as needed. The study makes an important contribution to the science of mental health nursing, as it is the first to test the usefulness of the Lithuanian IES-R to assess PTSS among the victims of workplace bullying.