Elsevier

Addictive Behaviors

Volume 32, Issue 12, December 2007, Pages 2788-2798
Addictive Behaviors

The psychometric utility of two self-report measures of PTSD among women substance users

https://doi.org/10.1016/j.addbeh.2007.04.016Get rights and content

Abstract

Given the high rates of posttraumatic stress disorder (PTSD) among substance users, integrated programs that target PTSD and substance use are recommended as best practice. To effectively implement such treatments, accurate and reliable PTSD screening instruments are needed. Unfortunately, no standardized PTSD measure has been validated among women substance abusers. Therefore, the goal of this investigation was to examine the psychometric utility of two PTSD measures to optimize the number of women clients correctly identified as meeting diagnostic criterion for PTSD. Forty-four women in residential substance use treatment were administered diagnostic interviews for PTSD (Clinician-Administered PTSD Scale) and then completed questionnaires regarding trauma exposure and related symptoms. In this group, 38.6% of the participants met diagnostic criteria for current PTSD. A score of 38 and above on the PTSD Checklist Civilian Version and a Penn Inventory score of 25 and above optimally maximized the number of women with PTSD identified and minimized false negative and false positive rates.

Introduction

The co-occurrence of substance use disorders (SUDs) and posttraumatic stress disorder (PTSD) for women is well documented in community and clinical samples. For example, in the National Comorbidity Survey 27.9% of the women with PTSD met criteria for lifetime alcohol abuse or dependence (Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995). Similarly, the Epidemiological Catchment Area findings revealed that women with PTSD were 1.4 times more likely to report substance abuse or dependence compared to women without PTSD (Regier et al., 1990). Additional findings from studies examining women with substance use disorders suggest that the current prevalence of PTSD was between 25% and 50% and lifetime prevalence of PTSD was between 19% and 50% (Brady et al., 1994, Moylan et al., 2001, Stewart et al., 1999). Further, clinical studies investigating women in substance-abuse treatment propose that rates of co-occurring PTSD and SUD are ranging from 30% to 59% (Brown et al., 1999, Najavits et al., 1998, Najavits et al., 1997). Research suggests that the co-occurrence of these disorders results in increased psychological symptomatology and poorer treatment outcomes, such as increased risk for relapse and non-compliance with aftercare (Brady et al., 1994, Brown et al., 1995, Najavits et al., 1997). Moreover, Saladin, Brady, Dansky and Kilpatrick (1995) found that women with co-morbid SUDs and PTSD report more symptoms in the avoidance and arousal clusters, as well as more sleep disturbance compared to women who present with only PTSD. Thus, symptom overlap between PTSD and SUDs makes accurate identification of those with PTSD difficult among individuals engaged in substance-abuse treatment; if PTSD can be identified in a cost-effective manner, integrated treatments focusing on both conditions can enhance treatment outcome (Brady et al., 1994, Elliott et al., 2005, Ruzek et al., 1998).

Although several diagnostic interviews and self-report questionnaires assess trauma history and PTSD, the psychometric utility of such screening tools in substance abusing populations is not well documented. In particular, only a few studies have explored the psychometric effectiveness of trauma exposure or PTSD scales among women substance users. For example, 118 adult inpatient and outpatient clients in a chemical dependency program were administered a modified version of the PTSD Symptom Scale Self-Report (MPSS-SR), a measure of frequency and severity of PTSD symptoms (Coffey, Dansky, Falsetti, Saladin, & Brady, 1998). Compared with the National Women's Study PTSD module, a structured PTSD diagnostic interview, the MPSS-SR correctly classified 89% of the PTSD positive patients. Further, a modified version of the Life Stressor Checklist (LSC-R) was employed to assess trauma history among 2729 treatment seeking women who met criteria for a SUD and an additional mental health disorder (McHugo et al., 2005). The findings suggest that the LSC-R was well received and the majority of items exhibited good test–retest reliability (Kappa = 0.32 to 0.97), with only 4 items exhibiting a Kappa below 0.40. The LSC-R also showed high test–retest reliability with the indicator variables of childhood sexual abuse, childhood physical abuse, adulthood sexual abuse, and adulthood physical abuse (Kappa = 0.51 to 0.76). Yet, it is unknown how well existing, standardized non-modified PTSD assessment instruments, validated in other groups, perform in a substance-abusing sample of women.

The current study compared two standardized self-report PTSD measures to the “gold standard” semi-structured PTSD diagnostic interview the Clinician-Administered PTSD Scale (CAPS; Blake et al., 1995) among substance-abusing women. Specifically, the aim of this study was to determine an optimal cut-off score that balances sensitivity, specificity, efficiency, positive and negative predictive values. In this context, sensitivity refers to the proportion of people who are correctly identified by the test as having PTSD, while specificity is the proportion of people who are correctly labeled by the test as not suffering from PTSD. Efficiency refers to the overall likelihood that true and false cases will be classified aptly. Positive predictive power (PPP) is the probability that someone has PTSD, given they test positive. In contrast, negative predictive power (NPP) is the probability that someone does not have PTSD, given they test negative (Kraemer, 1992). Clearly, the purpose of assessment determines which of these probabilities should be emphasized. In the vast majority of substance abuse contexts where it is critical that no one who has PTSD is overlooked; the false negative rate should be low (i.e.; sensitivity should be high). Also, it would be beneficial to rule out people who do not have PTSD to ensure they do not receive unnecessary treatment and referrals. Therefore, the false positive rate should be minimized (i.e.; specificity should be moderate to high). For positive and negative predictive power, a cut-off score that provides high predictive value and balances both is ideal. A second, two tier technique could also be implemented in screening for PTSD. The first screen would have high sensitivity and PPP with a score that ensures that few cases will be missed. The second screen would have high specificity and NPP to weed out false positives (Streiner, 2003). However, the two tier screening technique eliminates the possibility of missing a true case, but does not completely eradicate all false positive cases.

Section snippets

Participants

Fifty residents of a women's substance use disorder treatment facility were invited to volunteer in a research project to determine an optimal cut-off score for a PTSD self-report screener. Participants were recruited through the on-site clinicians and all 50 participants accepted the initial invitation to partake in the study. Six women did not complete the assessment battery due to discharge from the facility (n = 4) or discontinuation partially through the assessment (n = 2). The majority of the

Descriptive statistics

Descriptive statistics, including mean, standard deviation, and alpha, for the CAPS, PCL-C, and the Penn Inventory are presented in Table 2. Percentage of women endorsing lifetime substance use is displayed in Table 3. Substance use history was gathered using the Structured Clinician Interview for DSM-IV Axis I Disorders — Research Version (SCID-I; First, Gibbon, Spitzer, & Williams, 2001). The base rate of PTSD found in this sample of substance abusing women is 38.6%. The sensitivity, false

Summary

Until now, utility of the PCL-C and the Penn Inventory among substance abusing women was unknown. Our findings suggest that the psychometrically established and recommended existing cut-off scores, which were not tested among women substance abusers, do not optimally identify those with and without PTSD in our sample. The findings reveal that the PCL-C and the Penn Inventory are useful PTSD screening tools among women seeking substance-abuse treatment, although scoring criteria may need to be

Acknowledgements

We thankfully acknowledge the assistance of River Smith for her substantial contribution to this project and we recognize the entire research team, Jennifer Bristow, Shawn Kennedy, Alyssa Rippy, and Elizabeth Risch, for their time and proficiency in the assessment of study participants. We express sincere gratitude to the staff and clients at the residential treatment facility for their generous participation in this study.

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