Inventory of Complicated Grief (ICG)

1. Abstract

The Inventory of Complicated Grief (ICG) is a premier self-report psychometric instrument developed by Holly G. Prigerson and colleagues in 1995 to assess, quantify, and distinguish maladaptive, debilitating grief reactions from normative bereavement, major depressive episodes, and generalized anxiety. While conventional bereavement involves psychological distress that naturally attenuates over time, complicated grief—subsequently conceptualized as Prolonged Grief Disorder (PGD) within both the DSM-5-TR and the ICD-11—is characterized by chronic yearning, intense emotional pain, persistent disbelief regarding the finality of the death, bitterness, social detachment, and pervasive functional impairment. The standard ICG comprises 19 self-report items evaluated on a 5-point Likert scale ranging from 0 (Never) to 4 (Always), producing an overall score spectrum from 0 to 76. A validated clinical cut-off score of >25 establishes high risk for severe functional morbidity, including suicidal ideation, cardiovascular complications, immune dysregulation, and protracted psychosocial disability.

Extensive psychometric investigations have established that the ICG exhibits exceptional internal consistency, with initial validation studies reporting a Cronbach’s alpha of .94 and strong test-retest reliability (r = .80 over a six-month interval). Exploratory and confirmatory factor analyses typically reveal a predominantly unidimensional overarching construct reflecting an integrated bereavement-distress core, while multi-factor solutions identify distinct facets including persistent yearning, traumatized grief, behavioral avoidance, emotional detachment, and cognitive disintegration. Convergent and discriminant validity analyses confirm that the ICG captures a unique diagnostic entity distinct from the Beck Depression Inventory (BDI), the Hamilton Depression Rating Scale (HDRS), and post-traumatic stress measures. Translated into over twenty languages, the ICG remains an indispensable clinical screening instrument and the empirical benchmark in traumatology, palliative care, psycho-oncology, and clinical grief therapy.

2. Keywords

Inventory of Complicated Grief, ICG, Prolonged Grief Disorder, Bereavement, Pathological Grief, Attachment Theory, Traumatic Grief, Psychometrics, Factor Analysis, Holly G. Prigerson, Construct Validity, Clinical Assessment

3. Authors

The Inventory of Complicated Grief was designed and validated by an interdisciplinary team of psychiatric epidemiologists, psychologists, and biostatisticians led by Dr. Holly G. Prigerson. The principal validation publication arose from the Department of Psychiatry at the University of Pittsburgh School of Medicine and Western Psychiatric Institute and Clinic.

• Holly G. Prigerson, Ph.D. — Co-Director of the Center for Research on End-of-Life Care, Irving Sherwood Wright Professor of Geriatrics, and Professor of Sociology in Medicine at Weill Cornell Medicine, Cornell University, New York, NY, USA. Formerly at Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, and Harvard Medical School.
• Paul K. Maciejewski, Ph.D. — Co-Director of the Center for Research on End-of-Life Care and Associate Professor of Biostatistics in Medicine and Radiology at Weill Cornell Medicine, New York, NY, USA.
• Charles F. Reynolds III, M.D. — UPMC Endowed Professor of Geriatric Psychiatry Emeritus at the University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
• Frank J. Bierhals, M.S. — Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
• John T. Newsom, Ph.D. — Professor of Psychology at Portland State University, Portland, OR, USA.
• Amy Fasiczka, M.S. — Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
• Selby Jacobs, M.D., M.P.H. — Professor Emeritus of Psychiatry at the Yale University School of Medicine, New Haven, CT, USA.

Corresponding contact regarding the academic development of the instrument: Dr. Holly G. Prigerson, Center for Research on End-of-Life Care, Weill Cornell Medicine, 525 East 68th Street, Box 39, New York, NY 10065, USA. Email: [email protected].

4. Purpose

The primary clinical and empirical purpose of the Inventory of Complicated Grief (ICG) is to identify, differentiate, and quantify maladaptive, protracted psychological and functional reactions to interpersonal bereavement. Historically, psychiatric nosology lacked operationalized diagnostic criteria to separate normative grief reactions from severe psychiatric complications of bereavement. Bereaved persons experiencing severe emotional torment were frequently misdiagnosed with Major Depressive Disorder (MDD), Post-Traumatic Stress Disorder (PTSD), or generalized adjustment disorders. The ICG was engineered to demonstrate that complicated grief constitutes a discrete clinical syndrome with unique phenomenological, neurobiological, prognostic, and therapeutic characteristics.

Normal bereavement, though painful, typically exhibits a gradual trajectory of adaptation wherein the acute pangs of sorrow, crying spells, and yearning progressively recede, allowing the individual to integrate the reality of the loss, reinvest emotional energy in ongoing social relationships, and re-establish a sense of agency and existential purpose. In contrast, complicated grief represents a failure to negotiate this natural mourning trajectory. Individuals with complicated grief become psychologically paralyzed in an unyielding state of acute bereavement, experiencing chronic, intrusive yearning, intense separation distress, persistent emotional disbelief, pervasive bitterness, and inability to envision a meaningful future without the deceased.

The specific clinical and research objectives of the ICG include:

• Screening and Risk Stratification: Differentiating bereaved individuals who are navigating normative mourning from those exhibiting high-risk trajectories that require targeted therapeutic intervention. An established score cutoff (>25) alerts clinicians to severe pathological distress.
• Predictive Prognostication: Identifying individuals at increased risk for secondary psychiatric and physiological morbidities. Epidemiological studies utilizing the ICG have established that elevated complicated grief scores prospectively predict serious negative health outcomes, including incident hypertension, severe cardiac events, functional sleep impairment, heightened substance abuse, systemic immunological dysregulation, and persistent suicidal ideation independent of depressive symptoms.
• Outcome Assessment in Grief-Focused Psychotherapy: Serving as a rigorous, sensitive metric to track treatment efficacy in clinical trials evaluating specialized interventions, such as Complicated Grief Therapy (CGT) developed by M. Katherine Shear, cognitive-behavioral grief interventions, and targeted pharmacotherapeutic protocols. Standard antidepressant therapies (e.g., selective serotonin reuptake inhibitors) often yield minimal reductions on core ICG separation distress items despite reducing general depressive affect, highlighting the necessity of the ICG in evaluating targeted grief therapies.
• Nosological Validation: Providing the empirical foundation that facilitated the formal codification of Prolonged Grief Disorder as an official diagnostic category in the ICD-11 (code 6B42) and DSM-5-TR (code F43.8).

5. Psychological Construct

The psychological construct captured by the ICG is complicated grief (subsumed under the contemporary clinical diagnostic terminology of Prolonged Grief Disorder). Rather than reflecting diffuse dysphoria, this construct represents a multidimensional pathology rooted in severe attachment disruption, separation distress, and traumatic cognitive dissonance. The ICG operationalizes this construct across several distinct symptomatic clusters:

Separation Distress and Pervasive Yearning

The core dimension of complicated grief is unrelenting, preoccupying separation distress. Unlike depressive apathy, separation distress is an active, appetitive, and yearning emotional state. The individual experiences an intense, visceral craving for physical proximity and emotional communion with the deceased person (Item 4: “I feel myself longing for the person who died”). This yearning is often accompanied by compulsive behavioral searching, such as frequenting locations shared with the deceased or handling their physical possessions (Item 5: “I feel drawn to places and things associated with the person who died”). The cognitive apparatus is consumed by intrusive thoughts of the deceased, rendering everyday executive tasks difficult to sustain (Item 1: “I think about this person so much that it’s hard for me to do the things I normally do”).

Cognitive Impasse and Disbelief

A second fundamental component involves severe cognitive resistance to the reality and permanence of the death. The bereaved individual maintains an enduring psychological stance of disbelief, feeling stunned, emotionally frozen, or dazed by the loss (Item 7: “I feel disbelief over what happened”; Item 8: “I feel stunned or dazed over what happened”). The fundamental schema of reality cannot accommodate the death, resulting in an inability to psychologically accept that the loved one is irrevocably gone (Item 3: “I feel I cannot accept the death of the person who died”). In severe presentations, cognitive intrusion crosses into perceptual disturbances, such as auditory or visual pseudohallucinations (Item 14: “I hear the voice of the person who died speak to me”; Item 15: “I see the person who died stand before me”).

Traumatic Affect, Bitterness, and Existential Meaninglessness

Complicated grief entails profound affective dysregulation characterized by chronic anger, resentment, and existential despair. Individuals experience persistent bitterness regarding the circumstances or perceived injustice of the death (Item 6: “I can’t help feeling angry about his/her death”; Item 17: “I feel bitter over this person’s death”). This state often involves social envy directed at those whose interpersonal relationships remain intact (Item 18: “I feel envious of others who have not lost someone close”). Concurrently, survivor guilt surfaces as an intense feeling that one should have died instead (Item 16: “I feel that it is unfair that I should live when this person died”). When the attachment bond forms the singular scaffolding of the person’s identity, the loss precipitates severe existential disruption, manifested as feeling that life has become devoid of meaning or purpose (Item 13: “I feel that life is empty without the person who died”).

Social Alienation and Behavioral Avoidance

Rather than seeking consolation within their social network, individuals with complicated grief frequently withdraw into profound isolation. The capacity for relational trust and basic emotional empathy becomes deeply compromised (Item 9: “Ever since he/she died it is hard for me to trust people”; Item 10: “Ever since he/she died I feel like I have lost the ability to care about others or I feel distant from people I care about”). This relational withdrawal is compounded by pervasive loneliness (Item 19: “I feel lonely a great deal of the time ever since he/she died”). Concurrently, because reminders of the deceased trigger overwhelming affective dysregulation, many engage in rigid, phobic avoidance behaviors (Item 12: “I go out of my way to avoid reminders of the person who died”) and report that recollections provoke severe distress rather than comfort (Item 2: “Memories of the person who died upset me”).

Somatic Identification

A unique psychosomatic dimension evaluated by the ICG is somatic introjection or identification, wherein the bereaved individual manifests mirror symptoms or physical pain in anatomical regions corresponding to the terminal illness or cause of death of the deceased (Item 11: “I have pain in the same area of my body or have some of the same symptoms as the person who died”). This phenomenon underscores the profound failure of psychological boundary demarcation and self-other differentiation following loss.

6. Theoretical Framework

The construction and interpretation of the ICG rest upon several intersecting theoretical paradigms within psychological science: John Bowlby’s Attachment Theory, Cognitive-Behavioral Models of Complicated Grief, and Stress-Response Syndromes.

Bowlby’s Attachment Theory

The foundational bedrock of the ICG is Attachment Theory, pioneered by John Bowlby (1969, 1980) and expanded by Colin Murray Parkes (1972). Bowlby posited that human beings are biologically predisposed through evolutionary adaptation to establish and maintain primary attachment bonds with significant others. When an attachment figure is perceived as temporarily absent or threatened, the attachment behavioral system activates, producing protest, crying, visual searching, and intense separation anxiety intended to restore physical proximity.

In normative bereavement, the individual gradually moves through initial phases of shock, searching, and despair toward eventual reorganization as the finality of the attachment loss is gradually acknowledged. In complicated grief, however, the attachment system becomes locked in a state of chronic, unremitting hyperactivation. Individuals exhibiting anxious-ambivalent or preoccupied attachment styles are especially prone to this outcome. The death represents an irreparable fracture of the primary attachment security system; the individual remains trapped in the “protest and yearning” phase, unable to transition into psychological accommodation. The ICG explicitly captures this hyperactivated attachment state through items assessing longing, yearning, searching behaviors, and intense separation distress.

Cognitive-Behavioral Models of Prolonged Grief

Paul A. Boelen, Marcel A. van den Hout, and Jan van den Bout (2006), alongside M. Katherine Shear and colleagues (2005), developed cognitive-behavioral conceptualizations that explain the maintenance mechanisms measured by the ICG. According to Boelen’s model, complicated grief is maintained by three interconnected cognitive-behavioral processes:

1. Insufficient Integration of the Loss: The autobiographical memory of the death remains encapsulated and poorly integrated into general semantic and episodic memory networks. Because the reality of the death conflicts with the individual’s core beliefs regarding safety, predictability, and personal identity, the mind vacillates between traumatic intrusion and complete emotional numbness.
2. Maladaptive Beliefs and Appraisals: The individual holds catastrophic cognitions concerning their grief reactions (e.g., “If I allow myself to grieve, I will lose my mind” or “Enjoying life means I am betraying the deceased”) and catastrophic interpretations of the future (e.g., “My life is permanently over”).
3. Anxious and Depressive Avoidance: To evade the unbearable affect evoked by the reality of the loss, the individual engages in anxious avoidance (shunning external cues such as photographs, places, and possessions) or depressive avoidance (complete withdrawal from restorative vocational, leisure, and social pursuits). Ironically, this avoidance prevents cognitive processing and habituation, thereby entrenching the complicated grief cycle that the ICG quantitatively captures.

Traumatic Stress and Horowitz’s Stress-Response Paradigm

Mardi Horowitz’s (1976) formulation of stress-response syndromes also heavily influenced the creation of the ICG. Horowitz demonstrated that severe psychological trauma precipitates alternating phases of intrusive imagery and cognitive-affective avoidance. Prigerson and colleagues integrated this insight by conceptualizing complicated grief as an amalgam of separation distress and traumatic distress. The loss of a loved one can represent a psychically catastrophic event wherein the individual experiences intrusive reminders (analogous to PTSD re-experiencing), accompanied by profound detachment, shock, and estrangement from others.

7. Validity

The psychometric validity of the Inventory of Complicated Grief has been established across diverse clinical, geriatric, psychiatric, and cross-cultural cohorts.

Construct Validity and Factorial Independence

During its initial validation, Prigerson et al. (1995) administered the ICG to a sample of 97 bereaved individuals alongside the Beck Depression Inventory (BDI) and the Hamilton Depression Rating Scale (HDRS). The ICG exhibited strong construct validity, forming a unified construct distinct from depressive symptomatology. A critical finding supporting construct validity was that while ICG scores were moderately correlated with standard depression scales (Pearson r ranging from .50 to .65), partial correlations and regression modeling demonstrated that ICG scores predicted significant functional impairment (e.g., self-care deficits, occupational disability, impaired physical health) above and beyond the variance explained by depressive or generalized anxiety symptoms.

Convergent and Discriminant Validity

Convergent validity is confirmed by substantial positive correlations between the ICG and related measures of bereavement-related trauma, including the Impact of Event Scale (IES; r = .60 to .75) and the Texas Revised Inventory of Grief (TRIG; r = .70 to .82). Discriminant validity has been demonstrated through multi-trait multi-method matrices, exploratory factor analyses, and structural equation modeling. When items from the ICG, the BDI, and the PTSD Checklist (PCL) are factor-analyzed simultaneously, ICG items consistently load on a distinct separation-distress latent factor, demonstrating that complicated grief cannot be reduced to a subtype of major depression or generic post-traumatic stress.

Predictive and Criterion Validity

The predictive validity of the ICG is robust. Prigerson et al. (1995, 1997) conducted longitudinal follow-ups at 6, 12, 18, and 25 months post-loss. Elevated ICG scores assessed at initial evaluation reliably predicted adverse outcomes at subsequent timepoints, including:

• Substantially elevated incidence of cardiovascular pathology and new-onset hypertension.
• Marked increases in alcohol and hypnotic-sedative medication consumption.
• Persistent, active suicidal ideation, even after controlling for baseline depression scores.
• Severe disruption in basic physical and social role functioning, as assessed by the Medical Outcomes Study 36-Item Short Form (SF-36).

Diagnostic Cut-Off and Accuracy

Receiver Operating Characteristic (ROC) analyses established that an ICG total score of >25 provides optimal sensitivity (.93) and specificity (.93) for distinguishing complicated grief from normal grief reactions and predicting long-term psychological and physiological morbidity. This cut-off has been replicated across numerous subsequent clinical trials, serving as standard inclusion criteria for specialized complicated grief psychotherapeutic protocols.

8. Reliability

The ICG has demonstrated excellent psychometric reliability across multiple independent empirical evaluations.

Internal Consistency

In the original validation study by Prigerson et al. (1995), the ICG demonstrated an exceptionally high internal consistency, yielding a Cronbach’s alpha coefficient of α = .94 across the 19 items. Subsequent international psychometric investigations have continually replicated this high internal reliability:

• Dutch Adaptation (Boelen et al., 2003): Reported a Cronbach’s alpha of α = .94 in a sample of 262 bereaved adults.
• German Adaptation (Lumbeck et al., 2008): Yielded an internal consistency of α = .91 among bereaved psychiatric and non-psychiatric participants.
• Spanish Adaptation (Limonero et al., 2009): Reported an internal consistency coefficient of α = .88.
• Chinese Adaptation (Li et al., 2018): Demonstrated high internal reliability with α = .92.

Item-total correlation coefficients for all 19 items are consistently robust, rarely falling below .45, with central items—such as yearning (Item 4) and cognitive disbelief (Item 7)—frequently exhibiting item-total correlations exceeding .70.

Test-Retest Reliability

Test-retest stability was evaluated by Prigerson et al. in a subset of participants re-assessed across an extended six-month observation interval. Despite the natural passage of time, the Pearson correlation coefficient remained high at r = .80 (p < .001). In clinically untreated samples where complicated grief has settled into a chronic trajectory, the intraclass correlation coefficient (ICC) across shorter test-retest intervals (2 to 4 weeks) typically ranges from .88 to .95, confirming that the scale captures an enduring, trait-like psychological condition rather than fluctuating, transient mood swings.

9. Factor Analysis

The internal latent structure of the ICG has been subjected to extensive exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) across diverse cultural and demographic populations.

Unidimensional vs. Multidimensional Perspectives

In the seminal 1995 study by Prigerson et al., principal components analysis with varimax rotation suggested that a single primary factor accounted for the majority of the variance (44.3%), leading the authors to recommend treating the ICG as a primarily unidimensional instrument measuring an overall severity dimension of complicated grief. Item loadings on this primary general factor were uniformly high, with 17 of the 19 items demonstrating factor loadings ranging between .54 and .84.

Confirmatory Factor Analytic Models

Subsequent psychometric investigations employing larger, more diverse cohorts have revealed that while an omnibus second-order factor fits the data well, multidimensional sub-models offer superior representation of the distinct clinical features of prolonged grief. Common CFA structural findings in the published literature include:

• Three-Factor Models: Distinguishing between (1) Separation Distress (items reflecting yearning, intrusive thoughts of the deceased, and behavioral searching), (2) Traumatic Grief (items tapping anger, disbelief, shock, and feelings of injustice), and (3) Social and Identity Disruption (items capturing emptiness, inability to trust, detachment from others, and extreme loneliness).
• Four-Factor and Five-Factor Solutions: Research by Boelen et al. (2003) and others demonstrated that a multidimensional structure separating Cognitive-Emotional Invalidation, Emotional Shock, Yearning, Avoidance, and Functional Detachment yielded superior model fit statistics:
  • Comparative Fit Index (CFI) > .94
  • Tucker-Lewis Index (TLI) > .93
  • Root Mean Square Error of Approximation (RMSEA) ≤ .055
  • Standardized Root Mean Square Residual (SRMR) ≤ .048

Regardless of whether researchers utilize the multidimensional facet scores or the aggregated total score, the overarching latent construct displays exceptional structural coherence, confirming that the 19 items systematically capture the core facets of complicated grief pathology.

10. Instrument / Measurement Tool

• Name of Instrument: Inventory of Complicated Grief (ICG)
• Alternative Names: Traumatic Grief Inventory (early designation), Prigerson Complicated Grief Scale
• Assessment Type: Self-report psychometric rating scale
• Target Population: Bereaved adolescents and adults (typically administered ≥6 months post-bereavement to differentiate from acute normative mourning)
• Item Count: 19 items
• Response Format: 5-point Likert scale (scored 0 to 4)
  • 0 = Never
  • 1 = Seldom
  • 2 = Sometimes
  • 3 = Often
  • 4 = Always
• Scoring Procedure: All 19 items are scored from 0 to 4 and summed directly to generate a total composite score ranging from 0 to 76.
• Reverse-Scored Items: None (all items are keyed positively in the direction of pathological grief).
• Clinical Cut-Off Score: Total score > 25 indicates high risk for complicated grief / prolonged grief disorder and significant secondary functional, mental, and physical morbidity.
• Estimated Administration Time: 5 to 10 minutes.

11. Permissions & Fee and Test Year

The Inventory of Complicated Grief was first published in 1995 by Dr. Holly G. Prigerson and her research colleagues in Psychiatry Research.

• Copyright & Accessibility: The original academic validation publication is copyrighted by Elsevier Science Ireland Ltd. However, Dr. Holly G. Prigerson and the Center for Research on End-of-Life Care maintain an open academic access policy for clinical, non-profit educational, and scientific research purposes.
• Licensing and Clinical Usage: Academic investigators, clinical trainees, and non-commercial healthcare providers are generally permitted to utilize the ICG without payment of licensing fees, provided that appropriate bibliographic attribution is given to the original 1995 publication. Commercial entities, pharmaceutical clinical trials, and proprietary healthcare software platforms must obtain formal contractual clearance and licensing permissions from the copyright holder and authors prior to digital integration or deployment.

12. References

Boelen, P. A., van den Bout, J., de Keijser, J., & Hoijtink, H. (2003). Reliability and validity of the Dutch version of the Inventory of Complicated Grief (ICG). Journal of Clinical Psychology, 59(9), 1035–1045. https://doi.org/10.1002/jclp.10185

Boelen, P. A., van den Hout, M. A., & van den Bout, J. (2006). A cognitive-behavioral conceptualization of complicated grief. Clinical Psychology: Science and Practice, 13(2), 109–128. https://doi.org/10.1111/j.1468-2850.2006.00013.x

Bowlby, J. (1980). Attachment and loss: Vol. 3. Loss: Sadness and depression. Basic Books.

Horowitz, M. J., 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

Limonero, J. T., Lacasta, M. A., García, J. A., Gómez-Romero, M. J., & Mate-Méndez, J. (2009). Adaptación al castellano del Inventario de Duelo Complicado. Medicina Paliativa, 16(5), 291–297.

Maciejewski, P. K., Zhang, B., Block, S. D., & Prigerson, H. G. (2007). An empirical examination of the stage theory of grief. JAMA, 297(7), 716–723. https://doi.org/10.1001/jama.297.7.716

Parkes, C. M. (1972). Bereavement: Studies of grief in adult life. International Universities Press.

Prigerson, H. G., Bierhals, A. J., Kasl, S. V., Reynolds, C. F., Shear, M. K., Day, N., Beery, L. C., Newsom, J. T., & Jacobs, S. (1997). Traumatic grief as a risk factor for mental and physical morbidity. The American Journal of Psychiatry, 154(5), 616–623. https://doi.org/10.1176/ajp.154.5.616

Prigerson, H. G., Frank, E., Kasl, S. V., Reynolds, C. F., Anderson, B., Zubenko, G. S., Houck, P. R., George, C. J., & Kupfer, D. J. (1995). Complicated grief and bereavement-related depression as distinct disorders: Preliminary empirical validation in elderly bereaved spouses. The American Journal of Psychiatry, 152(1), 22–30. https://doi.org/10.1176/ajp.152.1.22

Prigerson, H. G., Maciejewski, P. K., Reynolds, C. F., Bierhals, A. J., Newsom, J. T., Fasiczka, A., Frank, E., Doman, J., & Miller, M. (1995). Inventory of Complicated Grief: A scale to measure maladaptive symptoms of loss. Psychiatry Research, 59(1–2), 65–79. https://doi.org/10.1016/0165-1781(95)02757-2

Shear, M. K., Frank, E., Houck, P. R., & Reynolds, C. F. (2005). Treatment of complicated grief: A randomized controlled trial. JAMA, 293(21), 2601–2608. https://doi.org/10.1001/jama.293.21.2601

13. Items of the Scale