Impact of Event Scale – Revised (IES-R)

1. Abstract

The Impact of Event Scale – Revised (IES-R) is one of the most widely utilized self-report psychometric instruments in clinical psychology, psychiatry, and traumatology for assessing current subjective distress resulting from a specific traumatic event. Developed by Daniel S. Weiss and Charles R. Marmar in 1997, the IES-R represents an essential revision of Mardi J. Horowitz’s original 15-item Impact of Event Scale (IES) published in 1979. While the original IES captured the two foundational response phases identified in early cognitive-processing models of trauma—Intrusion and Avoidance—the revised instrument incorporated a third dimension, Hyperarousal, to directly reflect the tripartite diagnostic criteria for Post-Traumatic Stress Disorder (PTSD) outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

The IES-R comprises 22 items evaluated along a 5-point rating scale ranging from 0 (“Not at all”) to 4 (“Extremely”), anchoring symptom severity to a specific traumatic incident experienced during the preceding seven days. Total scores range from 0 to 88, with subscale scores calculated either as sums or mean item scores for Intrusion (8 items), Avoidance (8 items), and Hyperarousal (6 items). Psychometrically, the instrument exhibits exceptional internal consistency across clinical, community, and cross-cultural cohorts, with Cronbach’s alpha (α) coefficients typically exceeding .85 for the subscales and .93 for the global scale. Confirmatory factor analyses generally corroborate the theoretical three-factor structure, though alternative four-factor models (e.g., King et al.’s emotional numbing and dysphoria configurations) have surfaced under specific empirical conditions. Convergent validity is robustly demonstrated through strong correlations with the Clinician-Administered PTSD Scale (CAPS), the PTSD Checklist (PCL), and various measures of general anxiety and depressive symptomatology. While the IES-R is not an exhaustive diagnostic tool due to its omission of DSM duration and functional impairment criteria, its diagnostic utility, sensitivity to treatment-induced change, and cross-cultural validity solidify its standing as an indispensable measure in trauma epidemiology and clinical practice.

2. Keywords

Impact of Event Scale – Revised, IES-R, Post-Traumatic Stress Disorder, PTSD assessment, Intrusion, Avoidance, Hyperarousal, psychometrics, trauma screening, subjective distress, factor analysis, construct validity

3. Authors

The Impact of Event Scale – Revised was formulated by:

• Daniel S. Weiss, Ph.D. — Professor Emeritus of Psychiatry, Department of Psychiatry and Behavioral Sciences, School of Medicine, University of California, San Francisco (UCSF), San Francisco, California, United States.
• Charles R. Marmar, M.D. — Lucius N. Littauer Professor of Psychiatry and Chair of the Department of Psychiatry, New York University (NYU) Grossman School of Medicine; Director of the Steven and Alexandra Cohen Veterans Center, New York, New York, United States.

The revised instrument heavily builds upon the foundational conceptualization and psychometric groundwork established by Mardi J. Horowitz, M.D., Professor of Psychiatry at the University of California, San Francisco, who pioneered the original 15-item Impact of Event Scale in 1979.

4. Purpose

The primary purpose of the Impact of Event Scale – Revised (IES-R) is to measure the current degree of subjective psychological distress experienced by an individual in response to a specifically identified traumatic life event. Unlike broad distress inventories or trait personality assessments, the IES-R is strictly an event-anchored, state-dependent measure. Respondents are instructed to identify a specific index stressor (e.g., motor vehicle collision, natural disaster, interpersonal violence, combat exposure, life-threatening medical diagnosis, occupational trauma) and rate the frequency and severity of post-traumatic stress symptoms experienced over the past 7 days.

Clinical Applications

In clinical practice, the IES-R serves as a rapid, reliable, and cost-effective screening mechanism. It assists clinicians in:

• Initial Triage and Screening: Identifying individuals exhibiting clinically significant post-traumatic reactions who require comprehensive diagnostic assessment via structured clinical interviews such as the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5).
• Treatment Planning: Profiling a client’s specific symptom cluster elevation (e.g., predominantly hyperarousal versus pervasive cognitive and behavioral avoidance), thereby aiding in tailoring psychotherapeutic interventions such as Prolonged Exposure (PE) or Cognitive Processing Therapy (CPT).
• Progress and Outcome Monitoring: Measuring longitudinal symptom fluctuation across the course of psychotherapeutic or pharmacological intervention. Because the recall window is standardized to the past week, the scale is sensitive to treatment-induced change over short intervals.

Research Applications

In clinical research, epidemiological investigations, and disaster mental health research, the IES-R provides a standardized, continuous metric of post-traumatic stress severity. It allows researchers to quantify trauma burden across diverse cohorts, evaluate the efficacy of randomized controlled trials (RCTs) targeting trauma recovery, and model structural pathways connecting trauma exposure, neurobiological markers, and psychosocial functioning.

Theoretical Rationale and Diagnostic Limits

The theoretical rationale for updating the original 1979 scale emerged from changes in psychiatric nosology. When the American Psychiatric Association published the DSM-IV in 1994, PTSD was formally conceptualized around three core symptom clusters: re-experiencing (Criterion B), avoidance/numbing (Criterion C), and physiological hyperarousal (Criterion D). The original IES evaluated only intrusion and avoidance, omitting hyperarousal symptoms such as hypervigilance, exaggerated startle, and physiological reactivity. Weiss and Marmar developed the IES-R to remediate this psychometric gap, ensuring the instrument aligned directly with contemporary psychiatric nosology while retaining Horowitz’s clinical phenomenology. However, the authors explicitly emphasize that the IES-R is an indicator of subjective distress and symptom severity, not a standalone diagnostic instrument, because it does not formally assess diagnostic Criterion A (event trauma parameters), Criterion E (duration > 1 month), or Criterion F (clinically significant functional impairment in social or occupational domains).

5. Psychological Construct

The IES-R evaluates post-traumatic stress symptomatology across three distinct, theoretically grounded psychological dimensions: Intrusion, Avoidance, and Hyperarousal.

1. Intrusion Subscale (8 Items)

The Intrusion construct reflects the involuntary, unbidden entry of trauma-related psychological material into conscious awareness. Traumatic memories are hypothesized to be inadequately integrated into autobiographical memory networks, resulting in spontaneous retrieval episodes triggered by internal or external cues. Within the IES-R, Intrusion encompasses several phenomenology-based manifestations:

• Intrusive Thoughts and Images: Unwanted, recurrent cognitive intrusions or mental imagery concerning the event (Item 6: “I thought about it when I didn’t mean to”; Item 9: “Pictures about it popped into my mind”).
• Episodic Flashbacks and Dissociative Re-experiencing: Severe lapses in temporal reality orientation wherein the individual feels or acts as though the trauma is recurring in the present moment (Item 14: “I found myself acting or feeling like I was back at that time”).
• Sleep Disturbances / Traumatic Nightmares: Sleep architecture fragmentation driven by trauma-specific dream content (Item 20: “I had dreams about it”; Item 2: “I had trouble staying asleep”).
• Affective and Perceptual Waves: Intense surges of distress precipitated by internal reminders (Item 1: “Any reminder brought back feelings about it”; Item 16: “I had waves of strong feelings about it”).

2. Avoidance Subscale (8 Items)

The Avoidance construct captures conscious cognitive, affective, and behavioral strategies deployed by the survivor to minimize, suppress, or escape from trauma-related stimuli and the excruciating emotional distress they provoke. This dimension embodies both active behavioral avoidance and emotional blunting/numbing:

• Behavioral Avoidance: Active evasion of external contexts, conversations, individuals, locations, or situations that stimulate memories of the trauma (Item 8: “I stayed away from reminders of it”; Item 22: “I tried not to talk about it”).
• Cognitive and Affective Suppression: Deliberate internal efforts to inhibit trauma-related ideation, memories, or emerging emotional responses (Item 5: “I avoided letting myself get upset when I thought about it or was reminded of it”; Item 11: “I tried not to think about it”; Item 17: “I tried to remove it from my memory”).
• Psychic Numbing and Dissociative De-realization: Subjective emotional blunting, state-dependent detachment, and perceptual defense mechanisms designed to decouple the trauma memory from autonomic panic (Item 7: “I felt as if it hadn’t happened or wasn’t real”; Item 13: “My feelings about it were kind of numb”).

3. Hyperarousal Subscale (6 Items)

The Hyperarousal construct, newly introduced in the revised version of the scale, captures persistent, tonic autonomic nervous system dysregulation, chronic sympathetic nervous system activation, and impaired inhibitory cognitive control. Traumatic exposure alters fronto-limbic circuitry—notably involving amygdala hyperresponsiveness and diminished medial prefrontal cortical inhibition—manifesting in physiological and behavioral vigilance:

• Somatic and Physiological Reactivity: Acute peripheral autonomic surges upon cue exposure, such as diaphoresis, dyspnea, tachycardia, or gastrointestinal distress (Item 19: “Reminders of it caused me to have physical reactions, such as sweating, trouble breathing, nausea, or a pounding heart”).
• Hypervigilance and Startle Reactivity: Chronic threat-monitoring behaviors and an exaggerated sensorimotor startle response (Item 10: “I was jumpy and easily startled”; Item 21: “I felt watchful and on-guard”).
• Irritability and Neuromuscular Agitation: Low tolerance for frustration, subjective anger, and autonomic agitation (Item 4: “I felt irritable and angry”).
• Attentional Disturbance and Sleep Initiation Deficits: Inability to concentrate due to disruptive threat appraisal and cognitive interference (Item 15: “I had trouble falling asleep”; Item 18: “I had trouble concentrating”).

6. Theoretical Framework

The IES-R is grounded in Mardi Horowitz’s Cognitive Information Processing Model of Stress Response Syndromes (Horowitz, 1976, 1979, 1986) and aligns with contemporary emotional processing and cognitive formulations of trauma (e.g., Foa & Kozak, 1986; Ehlers & Clark, 2000).

Horowitz’s Stress Response Model and the Completion Principle

Horowitz postulated that the human cognitive architecture operates on a fundamental drive toward cognitive synthesis, termed the completion principle. When an individual experiences an overwhelming traumatic event, the sensory, affective, and situational data generated by the experience vastly exceed the capacity of their pre-existing cognitive schemas (internal representations of safety, invulnerability, predictability, and control). To reconcile this discrepancy, the mind must store unintegrated traumatic information in an active memory buffer.

Because these traumatic representations are stored in active memory, they exert persistent pressure for cognitive integration, manifesting as intrusive re-experiencing phenomena (intrusive imagery, nightmares, flashbacks). However, because conscious access to this active memory elicits intolerable emotional pain, panic, and autonomic crisis, the individual’s cognitive defense mechanisms trigger secondary inhibitory processes. These defensive inhibitory operations manifest clinically as cognitive, affective, and behavioral avoidance, psychic numbing, and denial.

According to Horowitz, post-traumatic adjustment is characterized by an oscillatory dynamic between these two states:

1. The Intrusion Phase: Active trauma memory breaks through defense barriers, causing cognitive inundation, emotional flooding, and re-experiencing.
2. The Avoidance Phase: Exhaustion and intense distress activate cognitive defense networks, leading to emotional detachment, suppression, and behavioral withdrawal.

Under healthy psychological resolution, this oscillatory cycle gradually dampens as schemas are revised, the trauma memory is integrated into long-term autobiographical storage, and the active memory buffer clears. When processing stalls—often due to catastrophic cognitive appraisals or extreme affective flooding—the cycle stabilizes into chronic post-traumatic pathology.

Integration of Autonomic Hyperarousal and Modern Cognitive Theories

Although Horowitz recognized physiological arousal, the original 1979 IES omitted it from measurement. In revising the instrument, Weiss and Marmar incorporated insights from behavioral and biological models of fear conditioning. Classical conditioning paradigms demonstrate that during a life-threatening event, previously neutral contextual cues become conditioned stimuli ($CS$) paired with unconditioned autonomic terror ($UCS$). Exposure to these cues precipitates involuntary conditioned emotional responses governed by hyper-reactive amygdalar pathways.

Furthermore, Ehlers and Clark’s (2000) cognitive model posits that chronic PTSD occurs when individuals process the trauma and its aftermath in a manner that produces a sense of ongoing, imminent threat. This threat appraisal is maintained by two mutually reinforcing mechanisms: excessively negative appraisals of the event and its sequelae (e.g., “I am completely broken,” “The world is entirely lethal”), and problematic memory encoding characterized by poor contextual elaboration and intense perceptual priming. The IES-R precisely captures these dynamics: hyperarousal reflects the ongoing subjective sense of current threat, avoidance represents the dysfunctional behavioral and cognitive coping strategies that prevent memory re-evaluation, and intrusion reflects the poorly integrated, cue-driven retrieval of trauma memories.

7. Validity

The psychometric validity of the IES-R has been extensively confirmed across diverse clinical, military, emergency service, and disaster-exposed populations globally.

Construct and Structural Validity

Construct validity is substantiated by the scale’s capacity to discriminate between trauma-exposed individuals who meet clinical diagnostic thresholds for PTSD and those who do not. Weiss and Marmar (1997) initially established that individuals with established PTSD diagnoses scored significantly higher across all three subscales compared to trauma-exposed non-PTSD controls. Subsequent validation studies have replicated these distinctions across diverse trauma paradigms, including combat veterans, survivors of sexual assault, critical care survivors, and populations impacted by catastrophic environmental disasters.

Convergent and Discriminant Validity

Convergent validity is supported by strong, statistically significant correlations with gold-standard structured clinical interviews and alternative self-report trauma instruments:

• Clinician-Administered PTSD Scale (CAPS): Research by Creamer, Bell, and Failla (2003) in a large Australian sample of defense force personnel and treatment-seeking trauma survivors demonstrated that the IES-R total score correlated highly with the total CAPS severity score ($r = .84$). Subscale correlations between corresponding dimensions were equally robust: Intrusion ($r = .79$), Avoidance ($r = .71$), and Hyperarousal ($r = .78$).
• PTSD Checklist (PCL): Concordance between the IES-R and various iterations of the PTSD Checklist (such as the PCL-C, PCL-M, and PCL-5) regularly ranges between $r = .75$ and $r = .89$, confirming that both tools measure a common underlying psychopathological construct.
• General Distress, Anxiety, and Depression: The IES-R demonstrates moderate-to-high correlations with the Beck Depression Inventory (BDI) ($r = .55$ to $.68$) and the State-Trait Anxiety Inventory (STAI) ($r = .60$ to $.72$), reflecting shared negative affectivity.
• Discriminant Validity: Discriminant validity is demonstrated by markedly lower correlations ($r < .30$) with measures of unrelated constructs, such as generalized physical health status (e.g., SF-36 physical functioning subscale) and stable personality traits such as extraversion or conscientiousness.

Diagnostic Accuracy and Screening Cutoffs

Although Weiss and Marmar intentionally avoided prescribing a single rigid diagnostic cutoff—recommending that researchers select cutoffs based on the required balance of sensitivity and specificity—subsequent empirical receiver operating characteristic (ROC) analyses have established diagnostic benchmark ranges:

• Creamer et al. (2003): Identified a cutoff score of 33 (out of 88) as optimal for diagnosing PTSD against the CAPS criterion in a military and civilian sample, yielding a sensitivity of .91 and a specificity of .82.
• Asukai et al. (2002): In a validation of the Japanese IES-R, an optimal cutoff point of 24/25 was derived for screening purposes, maximizing sensitivity (.88) while maintaining acceptable specificity (.83).
• Rash, Coffey, Baschnagel, Drobes, and Saladin (2008): Identified a cutoff score of 22 as providing the best screening sensitivity in substance-dependent populations exposed to traumatic events.

8. Reliability

The IES-R exhibits high reliability across diverse demographic groups, cultural settings, and clinical configurations.

Internal Consistency

Internal consistency estimates for the IES-R total score and its three constituent subscales consistently meet or exceed rigorous psychometric standards for both research and individual clinical decision-making:

• Total Score: Cronbach’s alpha ($lpha$) for the 22-item composite scale universally falls between .92 and .96 across major studies (Weiss & Marmar, 1997; Creamer et al., 2003; Beck et al., 2008).
• Intrusion Subscale: Internal consistency ranges from $lpha = .87$ to .94.
• Avoidance Subscale: Internal consistency typically spans $lpha = .84$ to .89.
• Hyperarousal Subscale: Despite containing fewer items (6 items), internal consistency remains high, with alpha coefficients consistently observed between $lpha = .79$ and .91.

Test-Retest Reliability

Stability across repeated administrations highlights the instrument’s capacity to track symptom profiles reliably over time:

• In the original psychometric formulation by Weiss and Marmar (1997), test-retest reliability across a short-term interval (1 to 2 weeks) ranged from $r = .51$ to $.94$ across subscales in emergency responders and disaster-exposed individuals.
• Beck et al. (2008) examined motor vehicle accident survivors and demonstrated test-retest correlation coefficients of $r = .76$ for Intrusion, $r = .71$ for Avoidance, $r = .68$ for Hyperarousal, and $r = .75$ for the total score over a 14-day interval.
• Longer temporal intervals (e.g., 6 months) naturally exhibit lower stability coefficients ($r pprox .50-.60$), reflecting expected natural recovery trajectories and the therapeutic impact of clinical interventions.

9. Factor Analysis

The dimensional structure of the IES-R has been the subject of extensive empirical inquiry using both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

Exploratory Factor Analyses (EFA)

During the initial development of the instrument, Weiss and Marmar subjected the 22 items to principal components and maximum likelihood factor analyses with oblique rotations across multiple trauma samples. The analyses predominantly isolated three primary factors corresponding directly to the theoretical constructs of Intrusion, Avoidance, and Hyperarousal. Salient factor loadings (generally exceeding .50) were consistently observed for the designated items, with minimal cross-loading, supporting the scale’s initial construct architecture.

Confirmatory Factor Analyses (CFA) and Model Comparisons

Subsequent structural investigations utilizing CFA have examined how well the theoretical three-factor structure fits empirical data relative to alternative models:

• Theoretical Three-Factor Model: The original three-factor specification (Weiss & Marmar, 1997) generally yields acceptable-to-good goodness-of-fit indices across numerous populations (e.g., Comparative Fit Index [CFI] > .90; Tucker-Lewis Index [TLI] > .90; Root Mean Square Error of Approximation [RMSEA] < .06; Standardized Root Mean Square Residual [SRMR] < .05).
• Inter-Factor Correlations: Across virtually all CFA studies, the three latent factors demonstrate high inter-correlations, frequently ranging from $r = .70$ to $.88$. This high shared variance has led some psychometricians to argue that the IES-R is best modeled as a single higher-order general distress factor (“Post-Traumatic Stress”), which subsumes the three lower-order first-order factors.
• King et al.’s Four-Factor Model (Dysphoria vs. Numbing): In an influential CFA study, King, Leskin, King, and Weathers (1998) argued that DSM-IV PTSD is superiorly explained by a four-factor model that dissociates emotional numbing from active behavioral avoidance. When applied to the IES-R items, several investigators (e.g., Creamer et al., 2003) observed that partitioning the scale into Intrusion, Avoidance, Hyperarousal, and Numbing (or Dysphoria) resulted in marginally superior fit indices over the traditional three-factor solution.

Despite these empirical nuances, the original three-factor model remains the dominant paradigm in clinical assessment due to its alignment with clinical intervention strategies and practical scoring feasibility.

10. Instrument / Measurement Tool

• Test Name: Impact of Event Scale – Revised (IES-R)
• Alternative Title: IES-R
• Authors: Daniel S. Weiss, Ph.D. & Charles R. Marmar, M.D. (1997); original IES by Mardi J. Horowitz, M.D. (1979)
• Construct Measured: Current subjective psychological distress and post-traumatic stress symptomatology specific to an identified index event
• Test Type: Self-report rating scale
• Target Population: Adults and adolescents (aged 16+) exposed to a defined traumatic life event
• Administration Format: Paper-and-pencil questionnaire, clinician-administered survey, or computerized/online digital testing
• Administration Time: Approximately 5 to 10 minutes
• Recall Period: The past seven (7) days
• Item Count: 22 items
• Response Scale: 5-point rating scale (0 = Not at all, 1 = A little bit, 2 = Moderately, 3 = Quite a bit, 4 = Extremely)
• Subscale Composition:
  • Intrusion Subscale (8 items): Items 1, 2, 3, 6, 9, 14, 16, 20
  • Avoidance Subscale (8 items): Items 5, 7, 8, 11, 12, 13, 17, 22
  • Hyperarousal Subscale (6 items): Items 4, 10, 15, 18, 19, 21
• Scoring and Quantification:
  • Reverse Scored Items: None (all items are directly keyed).
  • Total Score Range: 0 to 88 (computed as the direct sum of all 22 items).
  • Subscale Scores: Can be expressed either as subscale sum totals or as mean item scores (subscale sum divided by the number of subscale items), ranging from 0 to 4.
  • Missing Data Handling: If more than 20% of items on any subscale are omitted, the subscale score is invalid. For single omitted items, mean imputation of that subscale can be utilized.
• Clinical Interpretation Guidelines:
  • 0 – 23: Normal / Subclinical distress; typical post-traumatic reaction without significant clinical impairment.
  • 24 – 32: Mild-to-moderate post-traumatic stress; clinically relevant symptoms that warrant monitoring and clinical follow-up.
  • 33 – 38: Moderate-to-severe post-traumatic stress; optimal screening cutoff indicating high risk of diagnosable PTSD.
  • 39 – 88: Severe subjective distress; severe post-traumatic pathology with marked functional impairment, indicating immediate need for comprehensive diagnostic assessment and intervention.

11. Permissions & Fee and Test Year

The Impact of Event Scale – Revised was published in 1997 as a book chapter authored by Daniel S. Weiss and Charles R. Marmar, titled “The Impact of Event Scale – Revised” in J. P. Wilson and T. M. Keane (Eds.), Assessing Psychological Trauma and PTSD (Guilford Press, New York).

Copyright and Licensing Policy

The IES-R was placed by its authors in the public domain for academic research and non-commercial clinical use. No licensing fees or formal publisher purchase orders are required for researchers or clinicians administering the instrument for diagnostic evaluation, therapy outcome assessment, or non-funded/funded scientific inquiries.

Commercial reproduction, incorporation into for-profit proprietary software platforms, or republication in commercial publications requires formal written permission from the copyright holders and Guilford Press. When utilizing the IES-R in clinical practice or academic publications, appropriate professional ethical standards require full citation of the original source publication (Weiss & Marmar, 1997).

12. References

• Asukai, N., Kato, H., Kawamura, N., Kim, Y., Yamamoto, K., Kishimoto, J., Miyake, Y., & Nishizono-Maher, A. (2002). Reliability and validity of the Japanese version of the Impact of Event Scale-Revised (IES-R-J): Four studies of different victims of traumatic events. The Journal of Nervous and Mental Disease, 190(3), 175–182. https://doi.org/10.1097/00005053-200203000-00006
• Beck, J. G., Grant, D. M., Read, J. P., Clapp, J. D., Coffey, S. F., Miller, L. M., & Palyo, S. A. (2008). The log-linear structure of posttraumatic stress disorder: A confirmatory factor analysis of the Impact of Event Scale-Revised. Journal of Anxiety Disorders, 22(4), 687–698. https://doi.org/10.1016/j.janxdis.2007.07.001
• Creamer, M., Bell, R., & Failla, S. (2003). Psychometric properties of the Impact of Event Scale – Revised. Behaviour Research and Therapy, 41(12), 1489–1496. https://doi.org/10.1016/j.brat.2003.07.010
• Ehlers, A., & Clark, D. M. (2000). A cognitive model of posttraumatic stress disorder. Behaviour Research and Therapy, 38(4), 319–345. https://doi.org/10.1016/s0005-7967(99)00123-0
• Foa, E. B., & Kozak, M. J. (1986). Emotional processing of fear: Exposure to corrective information. Psychological Bulletin, 99(1), 20–35. https://doi.org/10.1037/0033-2909.99.1.20
• Horowitz, M. J. (1976). Stress response syndromes. Jason Aronson.
• Horowitz, M., Wilner, N., & Alvarez, W. (1979). Impact of Event Scale: A measure of subjective stress. Psychosomatic Medicine, 41(3), 209–218. https://doi.org/10.1097/00006842-197905000-00004
• King, D. W., Leskin, G. A., King, L. A., & Weathers, F. W. (1998). Confirmatory factor analysis of the Clinician-Administered PTSD Scale: Evidence for the dimensionality of posttraumatic stress disorder. Psychological Assessment, 10(2), 90–96. https://doi.org/10.1037/1040-3590.10.2.90
• Rash, C. J., Coffey, S. F., Baschnagel, J. S., Drobes, D. J., & Saladin, M. E. (2008). Psychometric properties of the IES-R in traumatized substance-dependent individuals. Addictive Behaviors, 33(8), 1039–1047. https://doi.org/10.1016/j.addbeh.2008.04.004
• Weiss, D. S., & Marmar, C. R. (1997). The Impact of Event Scale – Revised. In J. P. Wilson & T. M. Keane (Eds.), Assessing psychological trauma and PTSD (pp. 399–411). Guilford Press.

13. Items of the Scale (Questionnaire)