Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Addict Behav. Author manuscript; available in PMC Aug 1, 2009.
Published in final edited form as:
PMCID: PMC2494706
NIHMSID: NIHMS56356

Psychometric Properties of the IES-R in Traumatized Substance Dependent Individuals with and without PTSD

Abstract

Posttraumatic stress disorder (PTSD) is common among treatment-seeking substance abusers. Despite the high prevalence of these co-occurring conditions, few PTSD screening tools have been evaluated for their utility in identifying PTSD in substance use disorder (SUD) populations. The present study evaluated the psychometric properties of the Impact of Event Scale- Revised (IES-R) in a sample of 124 substance dependent individuals. All participants had a history of a DSM-IV Criterion A traumatic event, and 71 individuals met diagnostic criteria for PTSD. Participants with comorbid PTSD reported significantly more symptoms of anxiety, depression, and PTSD compared to substance dependent individuals without PTSD. Acceptable internal consistency and convergent validity of the IES-R were established among a substance dependent sample. Examination of diagnostic effectiveness suggested a cutoff value of 22 as optimal for a substance using population, resulting in adequate classification accuracy, sensitivity, and specificity.

Keywords: comorbidity, Impact of Event Scale-Revised, posttraumatic stress disorder, cocaine dependence, alcohol dependence, traumatic events

1. Introduction

Among samples of treatment-seeking individuals with substance use disorders (SUDs), researchers have documented current posttraumatic stress disorder (PTSD) rates of 40% or higher (e.g., Bonin, Norton, Asmundson, Dicurzio, & Pidlubney, 2000; Dansky, Roitzsch, Brady & Saladin, 1997; Reynolds et al., 2005). Identification of PTSD comorbidity among substance abusers is clinically important, as presence of PTSD may lead to increased complexity in clinical presentation and treatment. Compared to patients with SUDs alone, patients with comorbid PTSD and SUDs exhibit higher addiction severity, are more likely to have comorbid affective, anxiety, and personality disorders, and are less likely to comply with aftercare (e.g., Back et al., 2000; Brady, Killeen, Saladin, Dansky, & Becker, 1994). These elevated symptoms may contribute to a higher number of inpatient admissions for individuals with comorbid PTSD and SUDs (Brown, Recupero, & Stout, 1995).

When PTSD is left untreated, substance abusers may be at high risk of experiencing additional traumatic events. In a study examining traumatized substance abusers receiving SUD treatment but not treatment for PTSD symptoms, individuals with PTSD were more likely to experience new traumatic events compared to traumatized individuals without PTSD despite improved PTSD global symptoms over the course of SUD treatment (Dansky, Brady, & Saladin, 1998). Accumulation of traumatic experiences may negatively impact substance treatment outcomes. Examining the impact of traumatic event history on relapse to substance abuse, Farley, Golding, Young, Mulligan, and Minkoff (2004) found that odds of repeated substance abuse treatments increased as a function of the number of different trauma type events experienced, indicating increased relapse risk for individuals with multiple traumatic events. Collectively, these studies suggest a cyclical and negative pattern of untreated PTSD, potential for experiencing additional traumatic events, and poorer substance abuse outcomes.

The careful assessment and treatment of PTSD represents a course of action by which the risk of future trauma exposure and diminished substance abuse outcomes can be reduced. However, PTSD cannot be treated if it is not detected, and there is evidence that PTSD is not often assessed in substance abuse treatment clinics. For example, Dansky and colleagues (1997) assessed 97 inpatient substance abusers for the presence of PTSD and found that 40% of the sample met criteria of current PTSD, yet diagnosis of PTSD was listed in only 15% of the discharge summaries. Interestingly, intake reports documented a history of physical and/or sexual abuse in approximately 50% of the sample. This study underscores the discrepancies between routine documentation of patients’ trauma history at intake (perhaps because of regulatory paperwork requirements) and lack of thorough assessment/diagnosis of PTSD in substance use treatment facilities.

In an effort to increase PTSD screening in substance abuse treatment clinics, Coffey, Dansky, Falsetti, Saladin, and Brady (1998) administered a modified version of the PTSD Symptom Scale – Self-Report (MPSS-SR; Falsetti, Resnick, Resick, & Kilpatrick, 1993) to 118 treatment-seeking substance users. The MPSS-SR is based on the PTSD Symptom Scale – Self-Report (PSS-SR; Foa, Riggs, Dancu, & Rothbaum, 1993), and measures the frequency and severity of PTSD symptoms. The MPSS-SR demonstrated good internal consistency and convergent validity in this SUD population. Using the National Women’s Study (NWS) PTSD Module (Kilpatrick, Resnick, Saunders, & Best, 1989; Resnick, 1996) to diagnose current PTSD according to DSM-III-R criteria (American Psychiatric Association [APA], 1987), Coffey et al. (1998) reported that a score of 28 on the MPSS-SR correctly identified 89% of individuals with current PTSD and correctly classified 74% of the sample on PTSD status.

More recently, Hyman, Garcia, Kemp, Mazure, and Sinha (2005) investigated the Early Trauma Inventory- Short Form (ETI-SF) in a sample of cocaine dependent individuals. While the ETI-SF provides a thorough investigation of childhood-related traumatic experiences, the utility of this instrument as a broad screener of PTSD is limited due to its explicit focus on childhood trauma. Kimerling, Trafton, and Nguyen (2006) examined a four-item screening instrument for PTSD (the PC-PTSD) in a sample of substance dependent veterans and established evidence of sound psychometric properties of the instrument as a screening tool. While the PC-PTSD was sensitive to detection of PTSD symptoms (Kimerling et al., 2006), the brevity of the instrument does not permit monitoring of symptoms over time.

Thus, despite recent growth in attention to PTSD screening and measurement issues for individuals with SUDs, there is a lack of instruments suitable for symptom measurement throughout treatment. Several areas of research investigating the comorbidity of SUD and PTSD suggest that accurate diagnosis and treatment of PTSD is important in substance abusing populations. First, high prevalence rates of trauma and PTSD among substance abusers are evident. Second, evidence (Coffey, Schumacher, Brady, & Dansky, 2007; Dansky et al., 1998) suggests PTSD symptoms decrease over the course of SUD treatment and abstinence in a manner consistent with identified patterns of reduced severity in mood symptoms during SUD treatment (Brown et al., 1995). Thus, reassessment of PTSD symptoms during and following SUD treatment will be consistent with recommendations for re-evaluation of mood symptoms during the course of SUD treatment (Brown et al., 1995). Lastly, as noted above, untreated PTSD, re-experiencing traumatic events, and poor substance abuse outcomes appear to be cyclically related (Dansky et al., 1998; Farley et al., 2004). An instrument that can be administered repeatedly is needed in order to fully monitor the course of PTSD symptoms. Unfortunately, only one of the above instruments (Coffey et al., 1998) has suitably broad coverage to apply to a range of PTSD-related traumas, and is useful for tracking of PTSD-related symptoms. However, this study used the now dated DSM-III-R criteria for PTSD rather than DSM-IV criteria.

In the present study, we sought to validate a commonly used instrument for assessment of PTSD symptomatology and severity in a sample of substance dependent individuals, filling a notable gap in assessment for this population. The current study had two primary aims. The first aim was to assess the psychometric properties of the Impact of Event Scale-Revised (IES-R) among treatment-seeking substance dependent individuals who had been exposed to a Criterion A traumatic event. The targeted recruitment of individuals with trauma exposure ensures a sample reflective of the population most appropriate for assessment of PTSD symptoms. Individuals with and without a concurrent diagnosis of PTSD were included. Internal consistency and construct validity of the IES-R were assessed. The second aim of the study was to establish a clinically useful cutoff score for the IES-R so that this widely used measure of PTSD symptomatology may be utilized in substance use treatment clinics to more easily screen for likelihood of a positive PTSD diagnosis. We hope that the provision of PTSD screening tools with appropriate cutoff scores may increase treatment access for substance dependent individuals with PTSD by focusing attention on PTSD prevalence and symptoms, and the need for PTSD services, in substance using populations. Ideally, this emphasis on detection and monitoring of PTSD symptoms will contribute to increased referrals and/or provision of PTSD treatments.

2. Method

2.1 Participants

Substance dependent participants (n = 128) were selected for the current analyses from a laboratory-based study examining reactivity to trauma and drug cues in 232 individuals with and without PTSD and SUDs (healthy controls and PTSD+ only participants were excluded from the present sample). Participants completed additional measures as part of the larger study, results of which are available elsewhere (Coffey et al., 2002; Saladin et al., 2003). Four cases were deleted due to missing data on the variables of interest. Participants were recruited from substance use treatment programs at a large university medical center and other local substance use treatment centers, increasing the likelihood of a representative treatment-seeking substance dependent sample. All participants met criteria for alcohol and/or cocaine dependence. Seventy-one participants met DSM-IV (APA, 1994) criteria for both PTSD and substance dependence diagnoses, with the remaining 53 participants meeting criteria for substance dependence only. However, all participants, regardless of PTSD status, satisfied DSM-IV Criterion A for PTSD with a crime-related trauma (e.g., physical or sexual assault either as a child or as an adult). Although all participants reported at least one crime-related trauma, individuals were not excluded from the study if non-crime-related traumas were also reported. Participants were excluded from the study if they met diagnostic criteria for a psychotic disorder, were experiencing a current manic episode, or were receiving treatment currently for PTSD. All procedures were approved by an Institutional Review Board and all participants provided informed consent. Participants received financial compensation for their participation.

2.2 Measures

Diagnostic inclusion and exclusion criteria were assessed via the Structured Clinical Interview for DSM-IV (SCID-IV; First, Spitzer, Gibbon, & Williams, 1996) which provides diagnoses for DSM-IV axis I disorders. The substance use module has shown good validity (Kidorf, Brooner, King, Stoller, & Wertz, 1998; Kranzler, Kadden, Babor, Tennen, & Rounsaville, 1996) and high interrater reliability (Skre, Onstad, Torgersen, & Kringlen, 1991) in earlier versions of the SCID (SCID-III-R; Spitzer & Williams, 1986). DSM-IV PTSD Criterion A and trauma history was assessed with the National Women’s Study (NWS) Event history-PTSD Module (Kilpatrick et al., 1989; Resnick, 1996). The NWS Event History-PTSD Module is a structured interview that uses open and closed-ended, behaviorally specific questions to evaluate a wide range of potentially traumatic events (e.g., sexual assault, physical assault; motor vehicle accidents, combat, etc.). The NWS Event History-PTSD Module demonstrates good concurrent validity with the SCID-PTSD module and acceptable reliability (Resnick, Kilpatrick, Dansky, Saunders, & Best, 1993). Participants were required to report at least one crime-related Criterion A event (direct physical or sexual assault during childhood or adulthood) for inclusion in the larger study. Once Criterion A was satisfied using the NWS Event History-PTSD Module, the Clinician Administered PTSD Scale (CAPS; Blake et al., 1995), a psychometrically sound, structured clinical interview, was used to assess Criteria B-F. The combined use of the NWS Event History-PTSD Module and CAPS has been used successfully in a number of studies (e.g., Back, Jackson, Sonne, & Brady, 2005; Brady, Dansky, Back, Foa, & Carroll, 2001; Coffey, Stasiewicz, Hughes, & Brimo, 2006; Coffey, Schumacher, Brady, & Dansky Cotton, 2007; Saladin et al., 2003).

The original Impact of Event Scale (IES; Horowitz, Wilner, & Alvarez, 1979) is one of the most widely used PTSD symptom scales in the literature (Joseph, 2000). The items of the IES are based on Horowitz’s model of emotional processing of trauma (Horowitz, 1976) and the scale was published just prior to the release of DSM-III (APA, 1980). With the change of symptom cluster conceptualization of PTSD in the DSM-III (i.e., re-experiencing/intrusions, avoidance, and hyperarousal), Horowitz’s two symptom model (intrusions and avoidance) no longer matched diagnostic criteria. In 1997, Weiss and Marmar, in an effort to make the IES more compatible with the DSM conceptualization of PTSD, modified the IES to assess the three symptom clusters identified in all versions of the DSM since DSM-III (Impact of Event Scale-Revised; IES-R; Weiss & Marmar, 1997). Weiss and Marmar largely retained the original intrusion and avoidance subscales and added a hyperarousal subscale. The Impact of Events Scale – Revised (IES-R; Weiss & Marmar, 1997) assesses self-reported PTSD symptomatology experienced in the past seven days. It consists of 22 items measured on a five point Likert scale (0–4, with labels of ‘Not at all’ to ‘Extremely’).

To measure depression and general psychiatric functioning, the Beck Depression Inventory (BDI; A. T. Beck, Rial, & Riskels, 1974) and the Symptom Checklist-90-Revised (SCL-90-R; Derogatis, 1994) were administered. The BDI is a well-validated 13-item self-report questionnaire that assesses symptoms of depression. The SCL-90-R is a 90-item checklist used to indicate general symptomatology related to DSM-IV psychiatric disorders, with well documented validity and reliability (Derogatis, 1994). The Short-Michigan Alcohol Screening Test (SMAST; Selzer, Vinokur, & van Rooijen, 1975) provided an index of alcohol use severity, and was administered to individuals identifying alcohol as their primary substance of choice. Individuals identifying cocaine as their primary substance completed the Drug Abuse Screening Test (DAST; Skinner, 1982).

2.3 Procedure

Diagnostic and self-report data were collected as part of a larger study assessing PTSD symptomatology and cue-reactivity. Initially, individuals were briefly screened either over the phone or in person for a substance dependence disorder and history of experiencing a traumatic event satisfying PTSD Criterion A. If an individual was likely to satisfy the substance dependence and trauma eligibility criteria, he or she was scheduled for an assessment session. An experienced research assistant obtained informed consent and conducted structured diagnostic interviews during the assessment session. Participants then completed various self-report measures including the BDI, DAST, SMAST, SCL-90-R, and IES-R reported here.

3. Data Analytic Procedure

Descriptive data and symptomatology measures were assessed for differences according to PTSD status using independent sample t-tests for continuous variables and chi-square tests for categorical data. Further analyses examined the performance of the IES-R in a substance dependent sample. Internal consistency was assessed within the total and subscale scores. Pearson’s Product-Moment correlations with relevant constructs (i.e., other measures of PTSD symptoms, anxiety, depression) provided evidence of convergent validity. The ability of the IES-R total score to discriminate between those with and without a PTSD diagnosis was examined using discriminant function analysis. Lastly, diagnostic effectiveness was evaluated for a range of possible cutoff scores. Consistent with the objective of this instrument as a screening tool, we prioritized identification of PTSD positive cases. Thus, our a priori objective for sensitivity was set at 0.90 (see also Coffey et al., 1998; Coffey, Gudmundsdottir, Beck, Palyo, & Miller, 2006). Sensitivity, specificity, positive predictive accuracy, and negative predictive accuracy were examined for each value within the selected range (selection of range values was guided by published cut-off values for the IES-R [i.e., Asukai et al., 2002; Creamer et al., 2003]).

4. Results

4.1 Participant Characteristics

Demographic data for the 124 treatment-seeking substance dependent participants are presented in Table 1 by PTSD status. The PTSD+ group had significantly more females, χ2 (1) = 17.66, p <.001, and White participants, χ2 (1) = 7.45, p =.006. PTSD+ and PTSD− groups were statistically equivalent in age, t(122) = 1.37, p =.17, marital status, χ2 (1) = 0.07, p =.80, educational achievement, χ2 (1) =1.65, p =.20, and unemployment rates, χ2 (1) = 2.65, p =.10.

Table 1
Demographics and self-reported measures by PTSD status in a substance dependent sample

Similar levels of alcohol/drug-related problems were present regardless of PTSD status, as indicated by statistically equivalent number of alcohol/drug inpatient, t(122) = −0.53, p =.60, and outpatient, t(122) = −0.06, p =.95, treatment attempts. SMAST scores, t(68) = −0.16, p =.87, and DAST scores, t(52) = −0.93, p =.36, were also statistically equivalent across PTSD status groups. For the total sample, 72.6% met criteria for alcohol dependence, and 50.8% were cocaine dependent. Cannabis use disorders were present in 16.1% of the sample. Abuse and dependence diagnoses for alcohol, cocaine, and cannabis were represented equivalently across the PTSD+ and PTSD− groups (all Fisher’s exact test p’s >.40). Opioid (2.4%) and sedative/hypnotics/anxiolytic (1.6%) use disorders, as well as alcohol or cocaine abuse (0.8% for each) were rare.

As stated above, all participants experienced at least one crime-related Criterion A trauma event in order to be included in the study. Table 2 presents the percentage of participants endorsing specific trauma types, as well as the percentage of individuals reporting additional traumas satisfying Criterion A within the same category. Three quarters (78.2%) of the sample reported a physical assault involving a weapon, with 63.9% of these individuals going on to experience additional physical assault involving weapons. Similarly, 75.9% of females endorsed forced or coerced sexual trauma involving vaginal penetration (with penis) by a male, and 50% of these women reported re-victimization of the same type. Physical assaults without weapon involvement and witnessing events involving serious injury or violent death were also highly prevalent. Overall, a significant portion of those who experienced one traumatic event went on to experience an additional trauma of the same type. These re-experiencing rates were particularly high for attacks with and without weapons, vaginal rape, and accidents.

Table 2
Percentages of Participants Experiencing DSM-IV PTSD Criterion A Trauma Types and Percentage of these Individuals Reporting Multiple Trauma Events of Same Type

Additional Axis I comorbid disorders were common. Of mood disorders, 23.4% met criteria for a Major Depressive Disorder, 9.7% for Dysthymic Disorder, 4% for Bipolar Disorders (I, II, and non-specific), and 11.3% for a Substance-induced Mood Disorder. Among anxiety disorders, 12.1% met criteria for Generalized Anxiety, 8.8% for Panic Disorders, 9.7% for Specific Phobias, 6.5% for Social Phobia, 4% for Obsessive-Compulsive Disorder, and 8.1% for Substance-induced Anxiety Disorder.

4.2 Symptom Levels and PTSD status

PTSD+ participants exhibited significantly greater symptoms than PTSD− participants on all mood and PTSD measures (see Table 1). Although PTSD+ participants were consistently higher in symptoms levels (as would be expected), PTSD− participants are not asymptomatic and exhibit some elevations in symptoms.

4.3 Reliability and Validity of the IES-R

Internal consistency was high among the total (Chronbach’s α = 0.95) and subscale scores (Intrusion α = 0.92; Avoidance α = 0.85; Hyperarousal α = 0.91). Convergent validity was demonstrated with consistent and high correlations between the IES-R total and subscale scores, and related measures of PTSD symptomatology and negative affect (see Table 3).

Table 3
Correlations between IES-R Total and Subscale Scores and Selected Measures in a Substance Using Sample

The IES-R was examined for diagnostic value in determining the presence of PTSD in a sample of SUD participants. A discriminant function analysis suggested that the overall model, and each of the IES-R subscales, discriminated between PTSD status groups. The model correctly identified PTSD status in 75.0% of the sample, and accounted for 31.0% of the variance explained, Wilk’s Lambda = 0.69, χ2(3, N = 124) = 44.77, p <.001. Standardized coefficients indicated that the Avoidance subscale made the largest unique contribution to group discrimination (0.69 compared to 0.24 for Hyperarousal and 0.18 for Intrusion). Similarly, examination of the structure matrix indicated that the Avoidance subscale (0.96) was most important contributor to the discrimination function, although hyperarousal (0.84) and intrusion (0.80) made strong contributions.

4.4 Determining Diagnostic Values

While the IES-R was not intended as a diagnostic instrument, it is commonly employed as a screening measure to assess the presence and severity of PTSD symptoms. To this end, a range of cutoff scores for the IES-R was examined for suitability with a substance dependent sample. Diagnostic effectiveness indices, including sensitivity, specificity, positive predictive accuracy, negative predictive accuracy, overall classification accuracy, and kappa values for the selected range of cutoff values are displayed in Table 4. As can be seen in Table 4, cutoff values of 22–24 meet the minimum a priori goal for sensitivity while maximizing specificity. With this range, 77% of the sample was correctly classified, with sensitivity at 92%, and specificity at 57%. The chance-corrected classification agreement was 50% (Kappa = 0.50), falling within the moderate range. Use of these cutoff values resulted in correct identification of 65 out of 71 PTSD+ cases and 30 out of 53 PTSD− cases.

Table 4
Diagnostic Effectiveness Indices for Select Cutoff Scores of the Impact of Events Scale- Revised (IES-R) in a Substance Using Sample

5. Discussion

On their own, SUDs and PTSD are highly prevalent disorders with pronounced impacts on functioning. The clinical picture among substance abusers is further complicated by the high rates of comorbid disorders, of which PTSD is overrepresented compared to the general population. Identification of substance abusers with comorbid PTSD is important given data suggesting these individuals suffer from greater severity in psychological symptoms, greater functional impairment, poorer prognosis, and are more likely to experience new traumatic events (Back et al., 2000; Brady et al., 1994; Ouimette, Ahrens, Moos, & Finney, 1997; Reynolds et al., 2005). Further, it appears that the PTSD comorbid diagnosis relative to other Axis I/SUD combinations causes a greater negative impact for the individual (Ouimette et al., 1997).

In the present sample of traumatized substance dependent participants, 57% met criteria for PTSD and other Axis I disorders were common. Consistent with the above literature, the substance dependent individuals with comorbid PTSD in this sample reported significantly greater severity in symptoms of anxiety, depression, and PTSD compared to the PTSD− group. Although we did not measure alcohol/drug consumption directly, the greater severity in affective symptomatology does not appear to be a function of greater drug/alcohol use, as the groups reported equivalent levels of alcohol- and drug-related problems. Although many studies report higher levels of addiction severity among individuals with comorbid PTSD and SUD’s (e.g., Back et al., 2000; Brady et al., 1994), some have found a pattern similar to that of the current study with comparable substance use severity, but greater PTSD-related and psychiatric symptoms (Reynolds et al., 2005).

Interestingly, the PTSD− group exhibited elevated PTSD-related symptoms, despite the fact that they had no diagnosis of PTSD. This may be reflective of symptom overlap captured by PTSD-related measures [e.g., arousal symptoms in PTSD and arousal during acute substance withdrawal (e.g., Coffey, Dansky, Carrigan, & Brady, 2000)], high rates of psychiatric comorbidity, increased trauma-related events among individuals with SUDs, and/or higher levels of generalized distress. The degree of overlap suggests that PTSD symptom inventories may have difficulty distinguishing presence or absence of PTSD in SUD groups because of this increase in reported symptoms. While it is possible that the presence of SUDs adds to general high levels of distress (as suggested by the elevated scores in the SUD/PTSD− group), the findings from the current study support the ability of the IES-R’s three symptom subscales to identify substance dependent individuals with and without PTSD.

Consistent with the other studies (e.g., J. G. Beck et al., 2008; Creamer et al., 2003), the IES-R scale scores were highly correlated with one another and with other measures of psychopathology (e.g., PTSD, depression, anxiety). Evidence of reliability and convergent validity of the IES-R for a substance dependent sample was established.

In terms of clinical utility, the IES-R subscales correctly classified three quarters of the sample, which represents an improvement upon chance-based prediction. In contrast to the J G. Beck et al. (2008) study, the current analyses found the avoidance scale to be most important for discrimination. This may be due to functional differences in the use of avoidance among substance abusers (indeed, substance use itself can be a form of avoidance). Further, these differences may suggest that the importance of avoidance behaviors and/or the ability of the avoidance subscale to discriminate between PTSD+ and PTSD− individuals may be population specific (trauma type and/or substance abusers). Sensitivity and specificity were comparable to estimates reported in other studies, slightly improved in comparison to the J G. Beck et al. (2008) study, and below that reported in the Creamer et al. (2003) study.

We recommend a cutoff value of 22 for the IES-R total score as optimal for use in an SUD sample. The low end of the 22–24 total score range was chosen because the screening objective is to identify as many PTSD+ individuals as possible with the knowledge that subsequent diagnostic testing will eliminate any false positive cases. However, with roughly equivalent properties for values 22–24, we encourage researchers and clinicians to adjust the cutoff value based on sample-specific presentations. The present recommended cutoff value is lower than the value of 33 suggested by the Creamer et al. (2003) study but in the range of cutoff values of 24/25 suggested by Asukai et al. (2002). The higher cutoff value proposed by the Creamer et al. (2003) study may reflect the population targeted, Vietnam veterans who likely have experienced a longer duration and greater severity of symptoms in comparison to our sample of individuals with substance dependence. The difference between cutoff scores may also be related to the fact that a diagnostic interview was not used to determine PTSD status for the community veterans in Creamer et al., rather an individual was classified as satisfying PTSD if his/her PCL score exceeded 50. Lastly, the differing cutoff scores may reflect base rate differences between the two samples. Although Creamer et al. did not report the prevalence of PTSD in the community sample, we can estimate the prevalence rate for the nontreatment-seeking community veteran sample via reports from the National Vietnam Veterans Readjustment Study (NVVRS), which estimate PTSD rates at 18.7% lifetime and 9.1% current for Vietnam veterans (Dohrenwend et al., 2006). Thus, base rates for the Creamer et al. study were likely lower than the 57% PTSD positive cases in this sample. As others (Brenner & Gefeller, 1997; Streiner, 2003) have noted, base rates and diagnostic misclassifications are related. The proportion of false positives increases in low prevalence conditions, and, in populations with high prevalence rates, the proportion of false negatives increases (Streiner, 2001). Selection of a higher cutoff value (to limit the number of false positives) in the Creamer et al. report may have been driven by the potential for higher rates of false positives given the comparatively lower community veteran sample base rate.

5.1 Limitations

All participants in the sample experienced at least one PTSD Criterion A event, which may reduce somewhat the generalizability of the findings presented here. Although this is a methodological concern, given the high percentages of treatment-seeking substance abusers with positive trauma histories (as high as 89–94%; Farley et al., 2004; Reynolds et al., 2005), this does not seem out of proportion with other clinical samples of individuals with SUDs. Further, the targeted sample (trauma experienced) is consistent with the use of the IES-R as a screening tool for PTSD. As the trauma events in the current study were restricted to crime-related events (e.g., physical assault, sexual abuse), it remains to be seen whether these results will generalize to other trauma types (e.g., combat, motor vehicle accidents). Motor vehicle accident trauma survivors, in particular, may represent a distinct subsample within PTSD. Blanchard, Hickling, Taylor, and Loos (1995) noted that the percentages of substance abuse/dependence were much lower in treatment seeking MVA samples compared to other reported estimates for PTSD samples.

Although use of the measure represented an improvement in diagnostic agreement over agreement by chance alone, the Kappa value was in the moderate range, leaving room for improvement. The majority of errors in classification fell toward over identification of PTSD cases (false positives), as we attempted to minimize the chance of failures to identify positive cases of PTSD (false negatives). As with any instrument used as a diagnostic screening tool, clinicians should be aware of the possibility of misidentifying true cases of PTSD, and reduce the potential for errors through the use of multiple sources of information (e.g., clinical interview).

5.2 Summary and Future Directions

Others have noted the importance of developing screening methods for PTSD in settings other than mental health clinics (Kimerling et al., 2004). Particularly among substance treatment clinics, where the percentages of individuals experiencing trauma and PTSD are higher than the general population (Bonin et al., 2000; Dansky et al., 1997; Reynolds et al., 2005), it is important to address PTSD symptomatology. Unfortunately, it appears that many of these diagnoses are overlooked within substance use treatment settings (Dansky et al., 1997). The slow growth in development and examination of commonly used PTSD symptom inventories within substance use samples is reflective of this general lack of attention to PTSD diagnosis. Few studies have been published with specific attention to the examination of the psychometric properties of PTSD inventories in this population, and unfortunately, at least one of these is outdated (Coffey et al., 1998).

Given the high comorbid rates of PTSD, establishing psychometric soundness for PTSD measures within a substance using sample seems particularly important. Despite the popularity of the IES-R, very little work has been conducted on establishing its psychometric properties in specific populations. The current study provides initial support for the use of the IES-R in individuals with substance dependence disorders, and establishes evidence of reliability and validity within this population. Future studies may wish to examine the factor structure of this instrument among substance abusers, as well as the hypothesized links between chronicity and severity of symptoms in relation to the IES-R factor structure. A longitudinal examination of the IES-R factor structure at different time points during treatment or following a traumatic event may provide clarification of PTSD cluster-specific symptom change over time.

Acknowledgments

This research was supported by National Institute on Drug Abuse grant DA 10595 awarded to Dr. Saladin, and preparation of this manuscript was partially supported by National Institute on Alcohol Abuse and Alcoholism grant AA 007290-27. We wish to thank Bonnie Dansky Cotton, Ph.D. and research assistants Jennifer Wieselquist, Lorri Ellen Campbell, Kristen Bycroft Robinson, Susan Quello, and Francis Beylotte III for their valuable contributions to this project.

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

References

  • American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 3. Washington, DC: Author; 1980. DSM-III.
  • American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 3- Revised. Washington, DC: Author; 1987. DSM-III-R.
  • American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4. Washington, DC: Author; 1994.
  • Asukai N, Kato H, Kawamura N, Kim Y, Yamamoto K, Kishimoto J, Miyake Y, Nishizono-Maher A. Reliability and validity of the Japanese-language version of the Impact of Event Scale- Revised (IES-R-J): Four studies of different traumatic events. Journal of Nervous and Mental Disease. 2002;190:175–182. [PubMed]
  • Back S, Dansky BS, Coffey SF, Saladin ME, Sonne S, Brady KT. Cocaine dependence with and without posttraumatic stress disorder: A comparison of substance use, trauma history, and psychiatric comorbidity. American Journal on Additions. 2000;9:51–62. [PubMed]
  • Back SE, Jackson JL, Sonne S, Brady KT. Alcohol dependence and posttraumatic stress disorder: differences in clinical presentation and response to cognitive–behavioral therapy by order of onset. Journal of Substance Abuse Treatment. 2005;29:29–37. [PubMed]
  • Beck JG, Grant DM, Read JP, Clapp JD, Coffey SF, Miller LM, Palyo SA. The Impact of Event Scale- Revised: Psychometric properties in a sample of motor vehicle accident survivors. Journal of Anxiety Disorders. 2008;22:187–198. [PMC free article] [PubMed]
  • Beck AT, Rial WY, Rickels K. Short form of Depression Inventory: Cross-validation. Psychological Reports. 1974;34:1184–1186. [PubMed]
  • Blake DD, Weathers FW, Nagy LM, Kaloupek DG, Gusman FD, Charney DS, Keane TM. The development of a Clinician-Administered PTSD Scale. Journal of Traumatic Stress. 1995;8:75–90. [PubMed]
  • Blanchard EB, Hickling EJ, Taylor AE, Loos W. Psychiatric morbidity associated with motor vehicle accidents. Journal of Nervous and Mental Disease. 1995;183:495–504. [PubMed]
  • Bonin MF, Norton GR, Asmundson GJ, Dicurzio S, Pidlubney S. Drinking away the hurt: The nature and prevalence of PTSD in substance abuse patients attending a community-based treatment program. Journal of Behavior Therapy and Experimental Psychiatry. 2000;31:55–66. [PubMed]
  • Brady KT, Dansky BS, Back SE, Foa EB, Carroll KM. Exposure therapy in the treatment of PTSD among cocaine-dependent individuals: Preliminary findings. Journal of Substance Abuse Treatment. 2001;21:47–54. [PubMed]
  • Brady KT, Killeen T, Saladin ME, Dansky B, Becker Comorbid substance abuse and posttraumatic stress disorder: Characteristics of women in treatment. American Journal on Addictions. 1994;3:160–164.
  • Brenner H, Gefeller O. Variation of sensitivity, specificity, likelihood ratios and predictive values with disease prevalence. Statistics in Medicine. 1997;16:981–991. [PubMed]
  • Brown PJ, Recupero PR, Stout R. PTSD substance abuse comorbidity and treatment utilization. Addictive Behaviors. 1995;20:251–254. [PubMed]
  • Brown SA, Inaba RK, Gillin JC, Schuckit MA, Stewart MA, Irwin MR. Alcoholism and affective disorder: Clinical course of depressive symptoms. American Journal of Psychiatry. 1995;152:45–52. [PubMed]
  • Coffey SF, Dansky BS, Carrigan M, Brady KT. Acute and protracted cocaine abstinence in an outpatient population: A prospective study of mood, sleep, and withdrawal symptoms. Drug and Alcohol Dependence. 2000;59:277–286. [PubMed]
  • Coffey SF, Dansky BS, Falsetti SA, Saladin ME, Brady KT. Screening for PTSD in a substance abuse sample: Psychometric properties of a modified version of the PTSD Symptom Scale Self-Report. Journal of Traumatic Stress. 1998;11:393–399. [PubMed]
  • Coffey SF, Gudmundsdottir B, Beck JG, Palyo SA, Miller L. Screening for PTSD in motor vehicle accident survivors using the PSS-SR and IES. Journal of Traumatic Stress. 2006;19:119–128. [PMC free article] [PubMed]
  • Coffey SF, Saladin ME, Drobes DJ, Brady KT, Dansky BS, Kilpatrick DG. Trauma and substance cue reactivity in individuals with comorbid posttraumatic stress disorder and cocaine or alcohol dependence. Drug and Alcohol Dependence. 2002;65:115–127. [PubMed]
  • Coffey SF, Schumacher JA, Brady KT, Cotton BD. Changes in PTSD symptomatology during acute and protracted alcohol and cocaine abstinence. Drug and Alcohol Dependence. 2007;87:241–248. [PMC free article] [PubMed]
  • Coffey SF, Stasiewicz PR, Hughes P, Brimo ML. Trauma-focused imaginal exposure with comorbid PTSD− alcohol dependent individuals: Revealing mechanisms of alcohol craving in a cue reactivity paradigm. Psychology of Addictive Behaviors. 2006;20:425–435. [PubMed]
  • Creamer M, Bell R, Failla S. Psychometric properties of the Impact of Event Scale-Revised. Behaviour Research & Therapy. 2003;41:1489–1496. [PubMed]
  • Dansky BS, Brady KT, Saladin ME. Untreated symptoms of PTSD among cocaine-dependent individuals. Journal of Substance Abuse Treatment. 1998;15:499–504. [PubMed]
  • Dansky BS, Roitzsch JC, Brady KT, Saladin ME. Posttraumatic stress disorder and substance abuse: Use of research in a clinical setting. Journal of Traumatic Stress. 1997;10:141–148. [PubMed]
  • Derogatis LR. Symptom Checklist 90-R: Administration, scoring and procedures. Minneapolis, MN: National Computer Systems; 1994.
  • Dohrenwend BP, Turner JB, Turse NA, Adams BG, Koenen KC, Marshall R. The psychological risk of Vietnam for U.S. veterans: A revisit with new data and methods. Science. 2006;313:979–982. [PMC free article] [PubMed]
  • Falsetti SA, Resnick HS, Resick PA, Kilpatrick DG. The modified PTSD Symptom Scale: A brief self-report measure of posttraumatic stress disorder. the Behavior Therapist. 1993;16:161–162.
  • Farley M, Golding JM, Young G, Mulligan M, Minkoff JR. Trauma history and relapse probability among patients seeking substance abuse treatment. Journal of Substance Abuse Treatment. 2004;27:161–167. [PubMed]
  • First MB, Spitzer RL, Gibbon M, Williams JBW. Structured Clinical Interview for Axis I DSM-IV Disorders - Patient Edition (With Psychotic Screen) New York: Biometrics Research Department, New York State Psychiatric Institute; 1996.
  • Foa EB, Riggs DS, Dancu CV, Rothbaum BO. Reliability and validity of a brief instrument for assessing posttraumatic stress disorder. Journal of Traumatic Stress. 1993;6:459–473.
  • Horowitz MJ. Stress response syndromes. 1. New York: Jason Aronson; 1976.
  • Horowitz M, Wilner N, Alvarez W. Impact of Event Scale: A measure of subjective stress. Psychosomatic Medicine. 1979;41:209–218. [PubMed]
  • Hyman SM, Garcia M, Kemp K, Mazure CM, Sinha R. Gender specific psychometric analysis of the early trauma inventory short form in cocaine dependent adults. Addictive Behaviors. 2005:847–852. [PMC free article] [PubMed]
  • Joseph S. Psychometric evaluation of Horowitz’s Impact of Event Scale: A review. Journal of Traumatic Stress. 2000;13:101–113. [PubMed]
  • Kidorf M, Brooner RK, King VL, Stoller KB, Wertz J. Predictive validity of cocaine, sedative, and alcohol dependence diagnoses. Journal of Consulting and Clinical Psychology. 1998;66:168–173. [PubMed]
  • KilpatrickDGResnick HS, Saunders BE, Best CL. The National Women’s Study PTSD Module. Charleston, SC: National Crime Victims Research and Treatment Center, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina; 1989. Unpublished instrument.
  • Kimerling R, Trafton &, Nguyen B. Validation of a brief screen for Post-traumatic Stress Disorder with substance use disorder patients. Addictive Behaviors. 2006;31:2074–2079. [PubMed]
  • Kimlering R, Ouimette P, Prins A, Nisco P, Lawler C, Cronkite R, Moos RH. Utility of a short screening scale for DSM-IV PTSD in primary care. Journal of General Internal Medicine. 2004;21:65–67. [PMC free article] [PubMed]
  • Kranzler HR, Kadden RM, Babor TF, Tennen H, Rounsaville BJ. Validity of the SCID in substance abuse patients. Addiction. 1996;91:859–868. [PubMed]
  • Ouimette PC, Ahrens C, Moos RH, Finney JW. Posttraumatic stress disorder in substance abuse patients: Relationship to 1-year posttreatment outcomes. Psychology of Addictive Behaviors. 1997;11:34–47.
  • Resnick H. Psychometric review of National Women’s Study (NWS) Event History-PTSD Module. In: Stamm BH, editor. Measurement of stress, trauma, and adaptation. Lutherville, MD: Sidran Press; 1996. pp. 214–217.
  • Resnick HS, Kilpatrick DG, Dansky BS, Saunders BE, Best CL. Prevalence of civilian trauma and posttraumatic stress disorder in a representative national sample of women. Journal of Consulting and Clinical Psychology. 1993;61:984–991. [PubMed]
  • Reynolds M, Mezey G, Chapman M, Wheeler M, Drummond C, Baldacchino A. Co-morbid post-traumatic stress disorder in a substance misusing clinical population. Drug and Alcohol Dependence. 2005;77:251–258. [PubMed]
  • Saladin ME, Drobes DJ, Coffey SF, Dansky BS, Brady KT, Kilpatrick DG. PTSD symptom severity as a predictor of cue-elicited drug craving in victims of violent crime. Addictive Behaviors. 2003;28:1611–1629. [PubMed]
  • Selzer ML, Vinokur A, van Rooijen L. A self-administered Short Michigan Alcoholism Screening Test (SMAST) Journal of Studies on Alcohol. 1975;36:117–126. [PubMed]
  • Skinner HA. The Drug Abuse Screening Test. Addictive Behaviors. 1982;7:363–371. [PubMed]
  • Skre I, Onstad S, Torgersen S, Kringlen E. High interrater reliability for the Structured Clinical Interview for DSM-III-R Axis I (SCID-I) Acta Psychiatrica Scandinavica. 1991;84:167–173. [PubMed]
  • Spitzer RL, Williams JBW. Structured Clinical Interview for DSM-III-R-Nonpatient version. New York: Biometrics Research Department, New York State Psychiatric Institute; 1986.
  • Streiner DL. Diagnosing tests: Using and misusing diagnostic and screening tests. Journal of Personality Assessment. 2003;81:209–219. [PubMed]
  • Weiss DS, Marmar CR. The Impact of Event Scale- Revised. In: Wilson JP, Keane TM, editors. Assessing psychological trauma and PTSD: A handbook for practitioners. New York: Guilford Press; 1997. pp. 399–411.
PubReader format: click here to try

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...