Prolonged grief disorder: Psychometric validation of criteria proposed for DSM-V and ICD-11

Abstract

Background: Bereavement is a universal experience, and its association with excess morbidity and mortality is well established. Nevertheless, grief becomes a serious health concern for a relative few. For such individuals, intense grief persists, is distressing and disabling, and may meet criteria as a distinct mental disorder. At present, grief is not recognized as a mental disorder in the DSM-IV or ICD-10. The goal of this study was to determine the psychometric validity of criteria for prolonged grief disorder (PGD) to enhance the detection and potential treatment of bereaved individuals at heightened risk of persistent distress and dysfunction.

Methods and findings: A total of 291 bereaved respondents were interviewed three times, grouped as 0-6, 6-12, and 12-24 mo post-loss. Item response theory (IRT) analyses derived the most informative, unbiased PGD symptoms. Combinatoric analyses identified the most sensitive and specific PGD algorithm that was then tested to evaluate its psychometric validity. Criteria require reactions to a significant loss that involve the experience of yearning (e.g., physical or emotional suffering as a result of the desired, but unfulfilled, reunion with the deceased) and at least five of the following nine symptoms experienced at least daily or to a disabling degree: feeling emotionally numb, stunned, or that life is meaningless; experiencing mistrust; bitterness over the loss; difficulty accepting the loss; identity confusion; avoidance of the reality of the loss; or difficulty moving on with life. Symptoms must be present at sufficiently high levels at least six mo from the death and be associated with functional impairment.

Conclusions: The criteria set for PGD appear able to identify bereaved persons at heightened risk for enduring distress and dysfunction. The results support the psychometric validity of the criteria for PGD that we propose for inclusion in DSM-V and ICD-11. Please see later in the article for Editors' Summary.

Figure 1. Relative item information as a function of the prolonged grief attribute for 22 candidate symptoms for PGD.

IRT IIF analysis of 22 binary candidate symptoms for PGD was performed using a 2-PL IRM. This figure displays item information as a function of the PG attribute for all 22 of these symptoms included in this IRM, relative to the maximum information for the most informative symptom, “inability to care about others since the death.” The horizontal line in the figure represents the standard used to discriminate between 16 informative candidate symptoms retained for further analysis, and six uninformative candidate symptoms excluded from further analysis (as indicated in Table 1).

Figure 2. Differential item functioning for two biased symptoms.

IRT DIF analysis of candidate symptoms for PGD was performed with respect to age (less than 65 y versus greater than or equal to 65 y), gender (male versus female), education (beyond versus not beyond high school), relationship to the deceased (spouse versus nonspouse), and time from loss (0–6 mo versus 6–12 mo post-loss). This figure displays IRT item characteristic curves (ICCs) for two symptoms found to differ with respect to relationship to the deceased (spouse versus nonspouse). The horizontal error bar associated with each ICC represents the standard error in the estimate of the location of the ICC with respect to the PG attribute. Of 16 informative symptoms examined, four symptoms displayed DIF and were excluded from further analysis (as indicated in Table 1).

Figure 3. Agreement between rater diagnoses and dichotomized prolonged grief attribute score diagnoses of PGD as a function of cutoff PG attribute score for diagnosis.

Dichotomized IRM PG attribute scores provide objective, reliable criterion standard diagnoses for PGD. This figure illustrates how rater diagnoses were used to establish a minimum-threshold cutoff PG attribute score for diagnosis of PGD (i.e., PG attribute score≥minimum-threshold cutoff PG attribute score). An optimal cutoff PG attribute score of 1 maximized agreement between rater diagnoses and dichotomized IRM PG attribute score diagnoses of PGD.

Figure 4. Alternative diagnostic algorithms for meeting symptom criteria for PGD.

Each data point in this figure represents the performance, in terms of sensitivity and specificity with respect to a criterion standard for PGD, of a unique “DSM-style” diagnostic algorithm for meeting symptom criteria for PGD. Each algorithm is specified in terms of one common, mandatory symptom, yearning, a specific set of n other, nonmandatory symptoms, and some minimum number of nonmandatory symptoms within this set, k, which one must have to satisfy the symptom criterion for PGD. Based on the current data, the optimal, most efficient algorithm requires having yearning and at least five of the following nine symptoms: avoidance of reminders of the deceased; trouble accepting the death; a perception that life is empty or meaningless without the deceased; bitterness or anger related to the loss; emotional numbness; feeling stunned, dazed or shocked; feeling that part of oneself died along with the deceased; difficulty in trusting others; and difficulty moving on with life.