The Structured Interview for Hoarding Disorder (SIHD): Development, usage and further validation
Introduction
The recent inclusion of hoarding disorder (HD) as a new diagnostic category in DSM-5 (American Psychiatric Association, 2013) has underscored the need for valid and reliable tools tailored to the task of its diagnosis. As highlighted in prior research (e.g., Mataix-Cols et al., 2010), since DSM-III “hoarding” has been framed as a symptom (either of obsessive–compulsive disorder [OCD] or obsessive–compulsive personality disorder [OCPD]) rather than a syndrome unto itself. Consistent with this conception, the assessment of hoarding behaviors has, historically, largely taken place in the context of an alternative condition or construct. For example, the Yale–Brown Obsessive Compulsive Scale (Y-BOCS)—widely viewed as the gold standard for assessing OCD symptom severity—prompts the evaluation of “hoarding and saving obsessions” and “hoarding and collecting compulsions” in its symptom checklist (Goodman et al., 1989, Goodman et al., 1989). While it is true that hoarding can be a symptom of OCD (Pertusa, Frost, & Mataix-Cols, 2010), it is increasingly acknowledged that these items fail to capture the core features of the syndrome (i.e., clutter, distress, interference, etc.), and provide an inadequate assessment of the severity of HD (Mataix-Cols et al., 2010).
In the wake of seminal work framing “hoarding” as an independent and definable construct (Frost & Hartl, 1996), the options for assessing hoarding features have expanded. Currently, a number of clinician and self-administered measures exist to assess hoarding features, in particular the severity of aspects such as difficulties discarding, clutter, and distress (for a review see Frost, Steketee, & Tolin, 2012). Some of the most widely used measures include the Hoarding Rating Scale—Interview (HRS-I; Tolin, Fitch, Frost, & Steketee, 2010), the Hoarding Rating Scale—Self Report (HRS-SR; Tolin, Frost, & Steketee, 2010), the Clutter Image Rating (CIR; Frost, Steketee, Tolin, & Renaud, 2008), and the Saving Inventory—Revised (SI-R; Frost, Steketee, & Grisham, 2004). These measures, typically, have empirically derived cut-offs that offer an indication of whether an individual is likely to have clinically-significant hoarding problems. However, while practical—particularly as a means of screening in population-based studies—these tools do not permit a formal diagnosis of HD as they cannot rule out other disorders that may also present with hoarding behavior.
Hoarding disorder is a complex diagnosis, often of exclusion, which requires the careful evaluation of the motivations underlying any hoarding activity. As such, diagnosing HD requires a direct and thorough psychopathological interview, ideally in the sufferer's living environment. As a diagnosis of HD requires endorsement of all core diagnostic criteria (Table 1), the aim of such an interview is to establish whether these features are present, and to rule out other general medical conditions (e.g., brain injury) and/or psychiatric disorders (e.g., OCD, autism spectrum disorders [ASD], psychosis) which also can account for hoarding behavior. Furthermore, an in-home interview offers the unique opportunity to complete a risk assessment—an important step as the clutter resulting from prolonged hoarding behavior may result in fire hazards, infestations, unsanitary living conditions, and additional health concerns (Snowdon et al., 2012, Tolin et al., 2008). In some cases, particularly where vulnerable children or elderly persons live in the cluttered property, these risk assessments may highlight the need for further intervention (e.g., fire brigade, social services; Tolin et al., 2008).
We have developed a semi-structured interview that maps directly onto the DSM-5 criteria for HD. The Structured Interview for Hoarding Disorder (SIHD) is intended to assist with the assessment of each diagnostic criterion required to determine an HD diagnosis, as well as the corresponding specifiers. Through a series of skip rules, it also aids clinicians in excluding other possible causes of hoarding with particular emphasis on the differential diagnosis of OCD and ASD (Criterion F). The SIHD also assists with the assessment of risk, and where helpful, may be used in conjunction with additional measures of hoarding severity (e.g., CIR).
While routinely used in all our studies, and in the work of other research groups, there is limited data on this interview's reliability and validity. The SIHD was recently employed in the London field trial for hoarding disorder (Mataix-Cols, Billotti, Fernández de la Cruz, & Nordsletten, 2013) and found to reliably discriminate, with high sensitivity and high specificity, between HD and other forms of object accumulation, including normative collecting, sub-clinical hoarding, and hoarding secondary to OCD. Across raters, reliability of the HD diagnosis and each individual HD criterion were also excellent (Mataix-Cols et al., 2013). The current study formally introduces the SIHD, extends investigation of its validity and reliability to a large, population-based sample, and offers practical recommendations for its use in both research and clinical settings.
Section snippets
Development
The SIHD was developed in 2010 alongside the drafting of the DSM-5 criteria. It was informed by our substantial experience assessing hoarding difficulties among the several hundred individuals who have participated in the team's research at the Institute of Psychiatry. Initially the instrument was organized into 3 main sub-sections designed to assist in: (1) the assessment of core HD diagnostic criteria, (2) the evaluation of HD specifiers, and (3) establishing the differential diagnosis with
Inter-rater reliability
K coefficients are reported in Table 2. The analyses demonstrated strong agreement between the two raters, with rater 1 and rater 2 largely overlapping on their individual criterion endorsements (range: 93.94–100%). The Kappa's corresponding to these values indicated “near perfect” agreement in the majority, with agreement on Criterion F (“Hoarding not better accounted for by the symptoms of another mental disorder”) resting at “substantial” (Landis & Koch, 1977). Regarding concurrence on the
Discussion
The SIHD has been applied in several studies to date, with the current investigation offering an additional test of the instrument's utility for diagnosing HD. Results from the present study indicate that the SIHD offers a highly reliable and valid tool for the assessment of HD, with the resulting diagnoses being highly replicable, relatable to existing hoarding measures, and appropriately divergent from measures of alternative conditions. Taken together with prior studies (e.g., Mataix-Cols et
Conclusion
The SIHD offers an intuitive and, according to current results and those of prior studies (Mataix-Cols et al., 2013), valid and reliable means of diagnosing HD. The instrument also facilitates the assessment of other relevant features, such as risk, which may be crucial for the case's clinical management. Ideally, the SIHD should be administered in the person's home by experienced interviewers, and incorporate all available sources of information. In most cases, its administration is relatively
Acknowledgements
SLH receives salary support from the National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and Institute of Psychiatry, King's College London. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health. The SELCoH study research was supported by the Biomedical Research Nucleus data management and informatics facility at South London and Maudsley NHS
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