Abstract

Introduction

Despite the long-held view that hoarding is a symptom of both obsessive-compulsive disorder (OCD) and obsessive-compulsive personality disorder (OCPD), increased evidence has emerged during the last 20 years suggesting that hoarding represents a distinct form of psychopathology. However, the arguments supporting key differences between hoarding and other OCD symptoms are not immune to criticism. For instance, some authors have expressed the fear that the separation of hoarding from OCD might be the first step toward the dismantling of what has been considered a valid and useful diagnosis so far (i.e., OCD). They are concerned that following this logic will lead to the creation of entities such as washing disorder, checking disorder, or ordering disorder. The fact that each OCD symptom dimension has some particularity does not indicate that it should comprise an independent disorder.

It is important to address whether splitting of diagnoses is indeed valuable in primary care and in a global context where the vast majority of the world has too few, rather than too many, possessions. Such a significant shift in the conceptualization of hoarding may be justifiable, however, if data shows it to be clinically useful and to translate into specific treatments and better outcomes. The present study reflects the discussion on the nosological status of hoarding carried out by the WHO ICD-11 Working Group on the Classification of Obsessive-Compulsive and Related Disorders, appointed by the WHO Department of Mental Health and Substance Abuse and reporting to the International Advisory Group for the Revision of ICD-10 Mental and Behavioural Disorders.

Historical background

Interest in the phenomenon of hoarding emerged in the early 20th century alongside the expansion of the psychoanalytical movement. It was particularly prompted by Freud's 1908 essay,¹1 . Freud S. Character and anal erotism. London: Hogarth; 1908. where he detailed the so-called “anal character,” i.e., “a regular combination of three peculiarities,” namely orderliness (i.e., “body cleanliness, reliability, and conscientiousness in the performance of petty duties”), obstinacy (i.e., “defiance, with which irascibility and vindictiveness may easily be associated”), and parsimony (which could “be exaggerated to the point of avarice”). More specifically, Freud's description of parsimony was perhaps one of the earliest sketches of what would later be called hoarding.

The concept of anal character markedly influenced the subsequent approach to hoarding.²2 . Stein DJ, Seedat S, Potocnik F. Hoarding: a review. Isr J Psychiatry Relat Sci. 1999;36:35-46. For instance, a few years later, in 1912, Jones identified two key aspects related to Freud's anal trait of parsimony, namely, “the refusal to give” and “the desire to gather, collect, and hoard.” Jones further suggested that money, books, time, food, and other objects were “copro-symbols,” i.e., fecal equivalents of the anal-erotic character. Hoarding possessions were also later conceptualized as phallic symbols (to represent their subjective value),³3 . Midgley N. Reading Anna Freud. London: Routledge Chapman & Hall; 2013. transitional objects (to account to for the close attachment children have to them),⁴4 . Winnicott DW. Transitional objects and transitional phenomena; a study of the first not-me possession. Int J Psychoanal. 1953;34:89-97. a pathological way of relating (i.e., a hoarding orientation),⁵5 . Fromm E. Man for himself: an inquiry into the psychology of ethics. New York: Open Road Media; 2013. and as last vestiges of the patients' object relations (aimed at maintaining ties with the external world),⁶6 . Arieti S. Interpretation of schizophrenia. New York: Basic Books; 1974. among others.

Initially, the term hoarding was introduced into the scientific terminology mainly to describe food-collecting behavior in animals, especially in rodents.⁷7 . Maier T. On phenomenology and classification of hoarding: a review. Acta Psychiatr Scand. 2004;110:323-37. In the 1960s, Bolman & Katz were the first to use the term to describe a human psychopathological phenomenon.⁸8 . Bolman WM, Katz AS. Hamburger hoarding: a case of symbolic cannibalism resembling Whitico psychosis. J Nerv Ment Dis. 1966;142:424-8. Later on, hoarding was progressively reported in a range of unrelated psychiatric disorders, from OCD to schizophrenia, thus raising questions about how best to classify such behaviors.⁷7 . Maier T. On phenomenology and classification of hoarding: a review. Acta Psychiatr Scand. 2004;110:323-37. In 1987, Greenberg⁹9 . Greenberg D. Compulsive hoarding. Am J Psychother. 1987;41:409-16. provided, in a description of four cases, several psychopathological features seen in primary hoarding, namely: onset in the third decade of life, preoccupation with hoarding to the exclusion of work and family, diminished insight, little interest in receiving treatment, and no attempt to curb the compulsion.

As theoretical approaches moved away from the classic emphasis on psychoanalytical factors toward a focus on functional relationships between cognitions and behaviors, alternate etiopathogenetic models were proposed.²2 . Stein DJ, Seedat S, Potocnik F. Hoarding: a review. Isr J Psychiatry Relat Sci. 1999;36:35-46. For instance, Furby¹⁰10 . Furby L. Possessions: toward a theory of their meaning and function throughout the life cycle. In: Bates PB, editor. Life span development and behavior. Vol 1. New York: Academic; 1978. described two types of behaviors on the basis of their underlying motivations: instrumental saving, where the possession fulfills some desire or purpose; and sentimental saving, where the possession serves as an extension of the self. More recently, Frost & Hartl¹¹11 . Frost RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. Behav Res Ther. 1996;34:341-50. have put forward a widely employed cognitive-behavioral model of hoarding, which conceptualizes hoarding as a consequence of: 1) information-processing deficits; 2) problems in forming emotional attachments; 3) behavioral avoidance; and 4) erroneous beliefs about the nature of possessions.

Is hoarding different from OCD and OCPD?

To early psychoanalysts, “anal traits” (the forerunner of today's OCPD) and OCD laid on the same spectrum and were both ascribed to common etiopathogenetic factors, and thus, understandably, shared several symptoms. Since parsimony (or, to use more recent terms, hoarding) was no exception, it was argued that hoarding could also be a symptom of OCD. Early theorists felt that hoarding could take on the characteristics of a compulsion,²2 . Stein DJ, Seedat S, Potocnik F. Hoarding: a review. Isr J Psychiatry Relat Sci. 1999;36:35-46. currently defined as behavior that is: i) recognized by the individual as its own; ii) resisted unsuccessfully; iii) not pleasurable in itself; and iv) unpleasantly repetitive.¹²12 . World Health Organization (WHO). The ICD-10 classification of mental and behavioural disorders: clinical descriptions and diagnostic guidelines [Internet]. [cited 2014 Ago 12]. Geneva: WHO; 1992. http://www.who.int/classifications/icd/en/bluebook.pdf
http://www.who.int/classifications/icd/e... Abraham,¹³13 . Abraham K. The anal character. In: Selected papers of Karl Abraham. New York: Brunner/Mazel; 1979. p. 384-9. for instance, described one of the first clear-cut hoarding-related cases of OCD in a woman with hoarding who, in order to discard personal belongings, had to emulate their unintentional loss by means of a complex and rigid ritual.

Perhaps as a consequence, hoarding obsessions and compulsions were included in several different obsessive-compulsive symptom checklists, such as the Yale-Brown Obsessive-Compulsive Symptom Checklist (Y-BOCS),¹⁴14 . Goodman WK, Price LH, Rasmussen SA, Mazure C, Delgado P, Heninger GR, et al. The Yale-Brown Obsessive Compulsive Scale. II. Validity. Arch Gen Psychiatry. 1989;46:1012-6.,¹⁵15 . Goodman WK, Price LH, Rasmussen SA, Mazure C, Fleischmann RL, Hill CL, et al. The Yale-Brown Obsessive Compulsive Scale. I. Development, use, and reliability. Arch Gen Psychiatry. 1989;46:1006-11. its dimensional version (the D-YBOCS),¹⁶16 . Rosario-Campos MC, Miguel EC, Quatrano S, Chacon P, Ferrao Y, Findley D, et al. The Dimensional Yale-Brown Obsessive-Compulsive Scale (DY-BOCS): an instrument for assessing obsessive-compulsive symptom dimensions. Mol Psychiatry. 2006;11:495-504. and the Obsessive-Compulsive Inventory,¹⁷17 . Foa EB, Huppert JD, Leiberg S, Langner R, Kichic R, Hajcak G, et al. The Obsessive-Compulsive Inventory: development and validation of a short version. Psychol Assess. 2002;14:485-96. and are reported in most (up to 52.7%) patients with OCD.¹⁸18 . Torres AR, Fontenelle LF, Ferrao YA, do Rosário MC, Torresan RC, Miguel EC, et al. Clinical features of obsessive-compulsive disorder with hoarding symptoms: a multicenter study. J Psychiatr Res. 2012;46:724-32. Hoarding was also described among patients with other obsessive-compulsive and related disorders (OCRD).¹⁹19 . Seedat S, Stein DJ. Hoarding in obsessive-compulsive disorder and related disorders: a preliminary report of 15 cases. Psychiatry Clin Neurosci. 2002;56:17-23. Indeed, in several nonclinical samples, significant correlations between the severity of hoarding and OCD symptoms were described using different self-report scales.²⁰20 . Frost RO, Gross RC. The hoarding of possessions. Behav Res Ther. 1993;31:367-81.

21 . Coles ME, Frost RO, Heimberg RG, Steketee G. Hoarding behaviors in a large college sample. Behav Res Ther. 2003;41:179-94.

22 . Frost RO, Steketee G, Grisham J. Measurement of compulsive hoarding: saving inventory-revised. Behav Res Ther. 2004;42:1163-82.

23 . Tortella-Feliu M, Fullana MA, Caseras X, Andion O, Torrubia R, Mataix-Cols D. Spanish version of the savings inventory-revised: adaptation, psychometric properties, and relationship to personality variables. Behav Modif. 2006;30:693-712.-²⁴24 . Fontenelle IS, Prazeres AM, Borges MC, Range BP, Versiani M, Fontenelle LF. The Brazilian Portuguese version of the Saving Inventory-Revised: internal consistency, test-retest reliability, and validity of a questionnaire to assess hoarding. Psychol Rep. 2010;106:279-96. Similarly, self-identified hoarders also described more OCD symptoms than nonclinical controls, thus suggesting an overlap between hoarding and OCD.²⁵25 . Frost RO, Krause MS, Steketee G. Hoarding and obsessive-compulsive symptoms. Behav Modif. 1996;20:116-32.

However, a number of observations have emerged suggesting that hoarding and other OCD symptoms are distinct conditions. For instance, thoughts related to hoarding were said to differ from OCD-related thoughts insofar as they were less intrusive,²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. characterized by less insight,²⁷27 . Tolin DF, Fitch KE, Frost RO, Steketee G. Family informants' perceptions of insight in compulsive hoarding. Cogn Ther Res. 2010;34:69-81. and more frequently associated with grief and/or anger.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. Conversely, in contrast to OCD compulsions, hoarding-related compulsions were frequently said to lead to pleasure and reward²⁸28 . Steketee G, Frost R, Kyrios M. Cognitive aspects of compulsive hoarding. Cogn Ther Res. 2003;27:463-79. and to worsen over each decade of life.²⁹29 . Ayers CR, Saxena S, Golshan S, Wetherell JL. Age at onset and clinical features of late life compulsive hoarding. Int J Geriatr Psychiatry. 2010;25:142-9.,³⁰30 . Grisham JR, Frost RO, Steketee G, Kim HJ, Hood S. Age of onset of compulsive hoarding. J Anxiety Disord. 2006;20:675-86. Furthermore, hoarding was reported to be a major problem in only a minority of patients with OCD,³¹31 . Foa EB, Kozak MJ, Goodman WK, Hollander E, Jenike MA, Rasmussen SA. DSM-IV field trial: obsessive-compulsive disorder. Am J Psychiatry. 1995;152:90-6. to result infrequently from prototypical OCD obsessions (i.e. aggressive, sexual, religious, contamination, or symmetry),³²32 . Pertusa A, Fullana MA, Singh S, Alonso P, Menchon JM, Mataix-Cols D. Compulsive hoarding: OCD symptom, distinct clinical syndrome, or both? Am J Psychiatry. 2008;165:1289-98.,³³33 . Matsunaga H, Hayashida K, Kiriike N, Nagata T, Stein DJ. Clinical features and treatment characteristics of compulsive hoarding in Japanese patients with obsessive-compulsive disorder. CNS Spectr. 2010;15:258-65. and to be poorly correlated with other non-hoarding OCD symptoms.³⁴34 . Wu KD, Watson D. Hoarding and its relation to obsessive-compulsive disorder. Behav Res Ther. 2005;43:897-921. Hoarding has also been associated with a pattern of neurobiological correlates that seem to differ from those observed in OCD, including genetic, cognitive, and neuroimaging findings (Table 1).²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. Finally, some, but not all,⁵³53 . Saxena S, Brody AL, Maidment KM, Baxter LR Jr. Paroxetine treatment of compulsive hoarding. J Psychiatr Res. 2007;41:481-7. studies suggest that hoarding patients exhibit poor adherence⁴⁹49 . Santana L, Fontenelle JM, Yucel M, Fontenelle LF. Rates and correlates of nonadherence to treatment in obsessive-compulsive disorder. J Psychiatr Pract. 2013;19:42-53.,⁵⁰50 . Mataix-Cols D, Marks IM, Greist JH, Kobak KA, Baer L. Obsessive-compulsive symptom dimensions as predictors of compliance with and response to behaviour therapy: results from a controlled trial. Psychother Psychosom. 2002;71:255-62. and poor response to conventional anti-OCD treatment that is not mediated by adherence.⁵⁰50 . Mataix-Cols D, Marks IM, Greist JH, Kobak KA, Baer L. Obsessive-compulsive symptom dimensions as predictors of compliance with and response to behaviour therapy: results from a controlled trial. Psychother Psychosom. 2002;71:255-62.

The WHO ICD-11 Working Group on the Classification of Obsessive-Compulsive and Related Disorders has attempted to list some counterarguments questioning the validity of these data, ranging from clinical to therapeutic and biological ones, in Table 1. However, close scrutiny of each argument and corresponding counterarguments tends to support the view that OCD and hoarding are, essentially, different phenomena. Hoarding also seems to be unrelated to OCPD phenomena. For instance, hoarding has been associated with a number of personality disorders other than OCPD, including the paranoid, schizotypal, and avoidant personality disorders.⁵⁴54 . Grisham JR, Steketee G, Frost RO. Interpersonal problems and emotional intelligence in compulsive hoarding. Depress Anxiety. 2008;25:E63-71.

55 . Samuels JF, Bienvenu OJ, Grados MA, Cullen B, Riddle MA, Liang KY, et al. Prevalence and correlates of hoarding behavior in a community-based sample. Behav Res Ther. 2008;46:836-44.-⁵⁶56 . Samuels JF, Bienvenu OJ 3rd, Pinto A, Fyer AJ, McCracken JT, Rauch SL, et al. Hoarding in obsessive-compulsive disorder: results from the OCD Collaborative Genetics Study. Behav Res Ther. 2007;45:673-86. Also, it has been suggested that deleting hoarding and miserliness items from the set of OCPD criteria may improve the validity of the OCPD diagnosis.⁵⁷57 . Grilo CM. Diagnostic efficiency of DSM-IV criteria for obsessive compulsive personality disorder in patients with binge eating disorder. Behav Res Ther. 2004;42:57-65.,⁵⁸58 . Hummelen B, Wilberg T, Pedersen G, Karterud S. The quality of the DSM-IV obsessive-compulsive personality disorder construct as a prototype category. J Nerv Ment Dis. 2008;196:446-55. Similarly, in longitudinal studies, only non-hoarding OCPD criteria, such as preoccupation with details, rigidity and stubbornness, and reluctance to delegate, were predictive of the diagnosis of OCPD two years later.⁵⁹59 . Grilo CM, Skodol AE, Gunderson JG, Sanislow CA, Stout RL, Shea MT, et al. Longitudinal diagnostic efficiency of DSM-IV criteria for obsessive-compulsive personality disorder: a 2-year prospective study. Acta Psychiatr Scand. 2004;110:64-8. Therefore, most studies suggest that the association between hoarding and OCPD is due to overlapping item content, i.e., because hoarding was assumed to be one of the eight criteria of OCPD.

Summary of the ICD-10 approach to hoarding

The ICD-10 approach might be considered neglectful for not even mentioning hoarding as a symptom or syndrome, dependent or independent of some other diagnosis. On the other hand, the DSM-IV-TR approach could be characterized as misleading by including it as a mere manifestation of OCD or OCPD. However, if faced with the need to code patients with prominent hoarding behaviors in the absence of OCD or OCPD, clinicians using the ICD-10 could still resort to the residual category F42.8, which denoted other OCD.

Comparing ICD vs. DSM approaches to hoarding

In contrast to the ICD-10 approach to hoarding described above, hoarding is implicitly mentioned in DSM-IV-TR as a symptom of OCD, when hoarding is severe, or of OCPD, when hoarding is milder. This may have been based on the idea that OCPD and OCD were due to common etiopathogenetic factors, resided on the same spectrum, and represented different severities of the same condition. In other words, if OCPD is milder OCD, and hoarding is OCPD, than severe hoarding is OCD. Nevertheless, as reported above, there is now evidence that the relationship between OCD and OCPD is probably due to symptom overlap.⁶⁰60 . Starcevic V, Brakoulias V. New diagnostic perspectives on obsessive-compulsive personality disorder and its links with other conditions. Curr Opin Psychiatry. 2014;27:62-7. Of note, clinicians were left with a problem if their patients had hoarding symptoms considered to be moderate in severity: no diagnosis was left for them in the DSM-IV-TR.

The approach to hoarding was modified in DSM-5.⁶¹61 . American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington: American Psychiatric Publishing; 2013.,⁶²62 . American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR). Arlington: American Psychiatric Publishing; 2000. Based on the differences between hoarding and OCD/OCPD, the DSM-5 classified hoarding disorder as a discrete condition. However, hoarding disorder was kept in the chapter on OCRD for historical reasons (i.e., the traditional link between hoarding and OCD/OCPD), because hoarders are usually seen in OCD clinics, and in line with the conservative approach adopted by DSM-5.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. The alternative option, i.e., including hoarding in an Appendix of Criteria Sets Provided for Further Study, was not adopted. Nevertheless, proponents of DSM-5 recognized that hoarding could be ascribed to different conditions, including major depressive disorder, schizophrenia or another psychotic disorder, dementia, autism spectrum disorders, and Prader-Willi syndrome, as well as OCD.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18. A summary of the different approaches to hoarding adopted by ICD-10, DSM-IV-TR, and DSM-5 is provided in Table 2.

Issues to be considered for ICD-11 related to clinical utility, global applicability, and applicability outside specialty mental health settings

There is good evidence supporting the inclusion of a specific hoarding disorder in the ICD-11.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. First, hoarding is not even mentioned as a problem in ICD-10. Second, as already acknowledged by DSM-5, the construct of hoarding is not subsumed by current conceptualizations of OCD or OCPD. If hoarding is left synonymous with OCD, ineffective anti-OCD treatments will be employed and patients will not be treated properly. Third, hoarding is a prevalent, yet neglected, condition. For example, recent epidemiological studies found current population estimates of hoarding of 5.8%, figures that are even higher than those reported for OCD.⁶³63 . Timpano KR, Exner C, Glaesmer H, Rief W, Keshaviah A, Brähler E, et al. The epidemiology of the proposed DSM-5 hoarding disorder: exploration of the acquisition specifier, associated features, and distress. J Clin Psychiatry. 2011;72:780-6; quiz 878-9. Finally, hoarding fits modern definitions of mental disorder according to different diagnostic manuals, which will be detailed below.⁶⁴64 . Stein DJ, Phillips KA, Bolton D, Fulford KW, Sadler JZ, Kendler KS. What is a mental/psychiatric disorder? From DSM-IV to DSM-V. Psychol Med. 2010;40:1759-65.,⁶⁵65 . International Advisory Group for the Revision of ICD-10 Mental and Behavioural Disorders. A conceptual framework for the revision of the ICD-10 classification of mental and behavioural disorders. World Psychiatry. 2011;10:86-92.

For instance, hoarding fulfills the ICD-11 criteria for mental disorders⁶⁵65 . International Advisory Group for the Revision of ICD-10 Mental and Behavioural Disorders. A conceptual framework for the revision of the ICD-10 classification of mental and behavioural disorders. World Psychiatry. 2011;10:86-92. as “a clinically recognizable set of symptoms or behaviors associated in most cases with distress and with interference with personal functions.” Hoarding also fits the more elaborate DSM-5 criteria for a mental disorder⁶⁴64 . Stein DJ, Phillips KA, Bolton D, Fulford KW, Sadler JZ, Kendler KS. What is a mental/psychiatric disorder? From DSM-IV to DSM-V. Psychol Med. 2010;40:1759-65. as “a behavioral or psychological syndrome or pattern that occurs in an individual,” that “leads to clinically significant distress or disability” (although hoarding symptoms are not distressful per se, the consequences of hoarding behaviors lead to distress and disability), that “is not merely an expectable response to common stressors and losses (e.g., the loss of a loved one) or a culturally sanctioned response to a particular event,” that “reflects an underlying psychobiological dysfunction,” and that “is not primarily a result of social deviance or conflicts with society.”

The concept of hoarding disorder is clinically useful.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. Hoarding is under-recognized and undertreated, may respond poorly to anti-OCD treatment, and often requires specific therapeutic approaches. The characterization of hoarding as a standalone disorder will potentially promote public awareness, decrease diagnostic ambiguities, facilitate professional communication, and stimulate research. Patients with hoarding disorder would be pleased to have their condition identified, as they frequently do not seem to perceive themselves as individuals suffering from typical OCD symptoms.⁶⁶66 . Mataix-Cols D, Fernández de la Cruz L, Nakao T, Pertusa A, DSM-5 Obsessive-Compulsive Spectrum Sub-Work Group of the Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders Work Group. Testing the validity and acceptability of the diagnostic criteria for Hoarding Disorder: a DSM-5 survey. Psychol Med. 2011;41:2475-84. Finally, adding hoarding specifiers (e.g., with and without squalor) to existing criteria would further enhance the clinical utility associated with the public health consequences of the disorder (see below).

Hoarding disorder diagnostic guidelines are likely to be globally applicable. For instance, in one study, about 90% of international psychiatrists thought hoarding disorder criteria would be very/somewhat acceptable for professionals and sufferers.⁶⁶66 . Mataix-Cols D, Fernández de la Cruz L, Nakao T, Pertusa A, DSM-5 Obsessive-Compulsive Spectrum Sub-Work Group of the Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders Work Group. Testing the validity and acceptability of the diagnostic criteria for Hoarding Disorder: a DSM-5 survey. Psychol Med. 2011;41:2475-84. Most experts (70%) supported the inclusion of hoarding disorder in the main DSM manual, whereas up to 50% of American Psychiatric Association members did.⁶⁶66 . Mataix-Cols D, Fernández de la Cruz L, Nakao T, Pertusa A, DSM-5 Obsessive-Compulsive Spectrum Sub-Work Group of the Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders Work Group. Testing the validity and acceptability of the diagnostic criteria for Hoarding Disorder: a DSM-5 survey. Psychol Med. 2011;41:2475-84. In another study, most participants with hoarding disorder (96%) felt that creating a new disorder would be very or somewhat acceptable, useful (96%), and not too stigmatizing (59%).⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18.

Although most of the work on hoarding disorder has been done in English-speaking countries and in predominantly Caucasian samples, hoarding has been assessed in OCD studies from Japan,³³33 . Matsunaga H, Hayashida K, Kiriike N, Nagata T, Stein DJ. Clinical features and treatment characteristics of compulsive hoarding in Japanese patients with obsessive-compulsive disorder. CNS Spectr. 2010;15:258-65. India,⁶⁷67 . Chakraborty V, Cherian AV, Math SB, Venkatasubramanian G, Thennarasu K, Mataix-Cols D, et al. Clinically significant hoarding in obsessive-compulsive disorder: results from an Indian study. Compr Psychiatry. 2012;53(8):1153-60. South Africa,¹⁹19 . Seedat S, Stein DJ. Hoarding in obsessive-compulsive disorder and related disorders: a preliminary report of 15 cases. Psychiatry Clin Neurosci. 2002;56:17-23. and Brazil.⁶⁸68 . Fontenelle LF, Mendlowicz MV, Soares ID, Versiani M. Patients with obsessive-compulsive disorder and hoarding symptoms: a distinctive clinical subtype? Compr Psychiatry. 2004;45:375-83. In these studies, OCD plus hoarding has been associated with a distinctive phenotype. Nevertheless, hoarding has not been examined in these and in other low- and middle-income countries outside of OCD patients. There is a pressing need to assess hoarding in developing contexts, collectivistic cultures, rural communities, and non-Caucasian individuals. For instance, in a recent Indian study, compared with OCD non-hoarders, OCD hoarders hailed exclusively from an urban background.⁶⁷67 . Chakraborty V, Cherian AV, Math SB, Venkatasubramanian G, Thennarasu K, Mataix-Cols D, et al. Clinically significant hoarding in obsessive-compulsive disorder: results from an Indian study. Compr Psychiatry. 2012;53(8):1153-60.

Finally, the concept of hoarding also seems to be applicable outside specialty mental health settings. Because of the complex, multifaceted nature of hoarding, some authors have called for and view “a multidisciplinary approach involving a variety of community organizations (e.g., social services, area agencies on aging, mental health agencies, code enforcement, public housing, law enforcement, fire, public health, home health agencies, and animal control agencies) as imperative and potentially the only successful response to hoarding.”⁶⁹69 . Koenig TL, Chapin R, Spano R. Using multidisciplinary teams to address ethical dilemmas with older adults who hoard. J Gerontol Soc Work. 2010;53:137-47. The extent to which the concept of hoarding disorder will be applicable outside specialty mental health settings in low- and middle-income countries is not completely clear. However, identifying hoarding disorder as a public health problem in these countries may stimulate local health organizations to develop tools and guidelines to intervene in most severe cases.

Alternatives for ICD-11 and rationale

The evidence reviewed above suggests that hoarding should be included in the ICD-11, as in DSM-5.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72. Although, as specified above, hoarding disorder has ties with many different conditions, its historical link with OCD and OCPD and the fact that most treatment-seeking hoarders are seen in OCD clinics suggest that, until more is known about its etiology, it would be reasonable to acknowledge hoarding disorder as an OCRD.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72.

A subsequent issue is the development of an optimal description of hoarding disorder for ICD-11. Current approaches to hoarding suggest that, besides clutter, there are two additional important behavioral elements for its characterization: difficult discarding and excessive acquisition. In addition, some evidence has arisen that cognitive features related to hoarding may also constitute one of its important dimensions. Diagnostic options for the cognitive, behavioral, and functional domains of hoarding disorder are described below.

Cognitive components of hoarding disorder

Although a significant component of hoarding is the presence of particular behaviors, a number of studies have described cognitive characteristics associated with problematic hoarding. The cognitive features of hoarding disorder can be conceptualized in terms of preoccupations, obsessions, overvalued ideas, cognitive deficits, or excessive attachments.

Preoccupation with the importance of possessions

While excessive preoccupations (or worries) have been classically reported to be a central feature of generalized anxiety disorder,⁷⁰70 . Shear MK. Generalized anxiety disorder in ICD-11. World Psychiatry. 2012;11:82-8. this term has also been employed in relation to the ICD-11 diagnostic guidelines for other OCRD (see other articles in this issue). Preoccupations are characterized by pervasiveness and excessive time occupied with specific obsessive concerns. A focus on preoccupations also provides clinicians a means of categorizing patients regarding the levels of insight in relation to hoarding-related thoughts. Nevertheless, some patients with hoarding do not seem to spend much time thinking about their possessions, unless they face the prospect of losing them.¹¹11 . Frost RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. Behav Res Ther. 1996;34:341-50.

Obsessions (i.e., thoughts, images, or urges/impulses) related to the importance of possessions

In an attempt to avoid unwanted confusion with generalized anxiety disorder-related preoccupations and to underline the relationship between hoarding disorder and other OCRD, one might argue that the cognitive component of hoarding disorder is best characterized as an obsession. DSM-5 has alluded to the obsessional quality of hoarding disorder when it describes a perceived need to save items and/or distress associated with discarding.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18. However, some authors have called attention to several differences between hoarding-related thoughts and prototypical obsessions, including the non-intrusive character of the former and the frequency with which they lead to other non-anxiety related emotions.²⁶26 . Mataix-Cols D, Frost RO, Pertusa A, Clark LA, Saxena S, Leckman JF, et al. Hoarding disorder: a new diagnosis for DSM-V? Depress Anxiety. 2010;27:556-72.

Overvalued ideas regarding the possible importance of possessions

Hoarding is frequently described as a condition associated with poor insight. Since some have characterized poor-insight obsessions as overvalued ideas,⁷¹71 . Veale D. Over-valued ideas: a conceptual analysis. Behav Res Ther. 2002;40:383-400. one might argue that hoarding-related thoughts could be better described in these terms. The fact that the concept of overvalued ideation also refers to how the self or identity of the individual is defined⁷¹71 . Veale D. Over-valued ideas: a conceptual analysis. Behav Res Ther. 2002;40:383-400. (and that hoarders frequently see their possessions as extensions of themselves) also supports the latter view. However, by using this label, one may miss the fact that hoarding-related symptoms may also be associated with good insight. For instance, in the London field trial, more than half of individuals with self-identified hoarding disorder were described as having good insight.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18.

Inattention and other information-processing deficits

A number of recent studies suggest that hoarding disorder patients exhibit a range of cognitive deficits, including inattention,⁷²72 . Fullana MA, Vilagut G, Mataix-Cols D, Adroher ND, Bruffaerts R, Bunting B, et al. Is ADHD in childhood associated with lifetime hoarding symptoms? An epidemiological study. Depress Anxiety. 2013;30:741-8.

73 . Tolin DF, Villavicencio A, Umbach A, Kurtz MM. Neuropsychological functioning in hoarding disorder. Psychiatry Res. 2011;189:413-8.

74 . Tolin DF, Villavicencio A. Inattention, but not OCD, predicts the core features of hoarding disorder. Behav Res Ther. 2011;49:120-5.-⁷⁵75 . Hartl TL, Duffany SR, Allen GJ, Steketee G, Frost RO. Relationships among compulsive hoarding, trauma, and attention-deficit/hyperactivity disorder. Behav Res Ther. 2005;43:269-76. executive dysfunction,⁷⁶76 . McMillan SG, Rees CS, Pestell C. An investigation of executive functioning, attention and working memory in compulsive hoarding. Behav Cogn Psychother. 2013;41:610-25.,⁷⁷77 . Grisham JR, Norberg MM, Williams AD, Certoma SP, Kadib R. Categorization and cognitive deficits in compulsive hoarding. Behav Res Ther. 2010;48:866-72. and memory problems.⁷³73 . Tolin DF, Villavicencio A, Umbach A, Kurtz MM. Neuropsychological functioning in hoarding disorder. Psychiatry Res. 2011;189:413-8.,⁷⁸78 . Blom RM, Samuels JF, Grados MA, Chen Y, Bienvenu OJ, Riddle MA, et al. Cognitive functioning in compulsive hoarding. J Anxiety Disord. 2011;25:1139-44.,⁷⁹79 . Hartl TL, Frost RO, Allen GJ, Deckersbach T, Steketee G, Duffany SR, et al. Actual and perceived memory deficits in individuals with compulsive hoarding. Depress Anxiety. 2004;20:59-69. Some models have posited that information-processing deficits play a significant role in the development of hoarding behaviors.¹¹11 . Frost RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. Behav Res Ther. 1996;34:341-50.,⁸⁰80 . Steketee G, Frost R. Compulsive hoarding: current status of the research. Clin Psychol Rev. 2003;23:905-27. According to these models, problems with attention may contribute to difficulty making decisions and lead to the accumulation of clutter.⁸⁰80 . Steketee G, Frost R. Compulsive hoarding: current status of the research. Clin Psychol Rev. 2003;23:905-27. However, there are also studies suggesting that attentional problems may be seen in only a small subset of patients with hoarding disorder.⁸¹81 . Hall BJ, Tolin DF, Frost RO, Steketee G. An exploration of comorbid symptoms and clinical correlates of clinically significant hoarding symptoms. Depress Anxiety. 2013;30:67-76. Although psychostimulants have been employed in the treatment of patients with hoarding disorder, they did not lead to any benefit for hoarding symptoms.⁸²82 . Rodriguez CI, Bender J Jr, Morrison S, Mehendru R, Tolin D, Simpson HB. Does extended release methylphenidate help adults with hoarding disorder?: a case series. J Clin Psychopharmacol. 2013;33:444-7.

Excessive attachments to possessions

One additional option is to characterize the cognitive component of hoarding as an excessive or pathological attachment to possessions. Although some might criticize the use of constructs with a psychodynamic flavor, it has been demonstrated that patients with hoarding disorder are excessively attached to their possessions, which they tend to hoard because of emotional significance (e.g., association with a significant event, person, place, or time), instrumental characteristics (e.g., usefulness), or intrinsic value (e.g., aesthetic qualities).⁸³83 . Steketee G, Frost R, Kyrios M. Cognitive aspects of compulsive hoarding. Cogn Ther Res. 2003;27:463-79. Critically, hoarding behaviors per se (but not their consequences) are non-distressing and/or are associated with pleasure or enjoyment.

Behavioral components of hoarding disorder

While hoarding must be associated with some degree of clutter to be clinically significant, the extent to which hoarding-related behaviors must be present is not so straightforward. At least theoretically, clutter may be the ultimate result of a positive balance between acquired and discarded possessions. For instance, an individual can develop hoarding/clutter: because (i) he/she acquires too many items despite not having problems discarding them; because (ii) he/she discards too few items (if any), despite not having excessive acquisition behaviors; or (iii) because he/she acquires too many items and discards too few at the same time. To help clarify this issue, some options for what can be considered key behavioral elements of hoarding disorder have been outlined below.

Difficult discarding as a core symptom

This alternative was adopted by the DSM-5, which requires the presence of persistent difficulty discarding or parting with possessions, regardless of their actual value, for a diagnosis of hoarding disorder. The problem with this diagnostic requirement is that it would eliminate the possibility of diagnosing hoarding disorder in individuals who exhibit clutter as a result of excessive acquisition in the absence of difficult discarding. For example, in a German population-based sample, the correlations between the clutter subscale of the German Compulsive Hoarding Inventory and the Compulsive Buying Scale scores were even higher (r = 0.547) than those found between the difficulty discarding subscale of the German Compulsive Hoarding Inventory and the same buying scale (r = 0.330).⁸⁴84 . Mueller A, Mitchell JE, Crosby RD, Glaesmer H, de Zwaan M. The prevalence of compulsive hoarding and its association with compulsive buying in a German population-based sample. Behav Res Ther. 2009;47:705-9. Nevertheless, despite the theoretical plausibility of this clinical picture, patients with excessive acquisition and clutter in the absence of inability to discard are probably not often seen by clinicians.

Excessive acquisition as a core symptom

It has been suggested that not all subjects with hoarding disorder exhibit excessive acquisition. Accordingly, DSM-5 included excessive acquisition as a specifier. For instance, in a study with self-identified hoarders, one-third of patients with hoarding disorder did not endorse excessive acquisition behaviors, including compulsive shopping, excessive acquisition of free items, and kleptomania.⁶³63 . Timpano KR, Exner C, Glaesmer H, Rief W, Keshaviah A, Brähler E, et al. The epidemiology of the proposed DSM-5 hoarding disorder: exploration of the acquisition specifier, associated features, and distress. J Clin Psychiatry. 2011;72:780-6; quiz 878-9. Nevertheless, it has also been suggested that patients who deny current acquisition problems often report a history of acquisition problems in the past and active avoidance of acquisition cues.⁸⁵85 . Frost RO, Rosenfield E, Steketee G, Tolin DF. An examination of excessive acquisition in hoarding disorder. J Obsessive Compuls Relat Disord. 2013;2:338-345. In some cases, acquisition may only surface when cues that trigger urges to acquire are no longer avoided.⁸⁵85 . Frost RO, Rosenfield E, Steketee G, Tolin DF. An examination of excessive acquisition in hoarding disorder. J Obsessive Compuls Relat Disord. 2013;2:338-345. In addition, there has also been some dispute on whether lack of excessive acquisition could reflect poor insight and individuals' inability to appraise their acquisition behaviors.⁸⁶86 . Frost RO, Tolin DF, Steketee G, Fitch KE, Selbo-Bruns A. Excessive acquisition in hoarding. J Anxiety Disord. 2009;23:632-9.

Both difficult discarding and excessive acquisition as core symptoms

This alternative would require the presence of the two classical hoarding-related behavioral elements, as in early studies on hoarding behavior.²⁰20 . Frost RO, Gross RC. The hoarding of possessions. Behav Res Ther. 1993;31:367-81. Although they would raise the diagnostic threshold for hoarding disorder, these diagnostic guidelines would also prompt greater search for excessive acquisition symptoms by clinicians (including urges, behaviors, and related avoidance) and better differentiation from other forms of pathological accumulation. It would also be in accordance with recent studies suggesting that excessive acquisition and difficult discarding belong to a unidimensional hoarding phenotype.⁸⁷87 . Meyer JF, Frost RO, Brown TA, Steketee G, Tolin DF. A Multitrait-Multimethod Matrix Investigation of Hoarding. J Obsessive Compuls Relat Disord. 2013;2:273-80. As reported above, this alternative would reinforce the need to involve family members, friends, or other related individuals in the diagnostic assessment, given that patients with hoarding may have poor insight into their acquisition behaviors.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18.,⁶³63 . Timpano KR, Exner C, Glaesmer H, Rief W, Keshaviah A, Brähler E, et al. The epidemiology of the proposed DSM-5 hoarding disorder: exploration of the acquisition specifier, associated features, and distress. J Clin Psychiatry. 2011;72:780-6; quiz 878-9.,⁸⁶86 . Frost RO, Tolin DF, Steketee G, Fitch KE, Selbo-Bruns A. Excessive acquisition in hoarding. J Anxiety Disord. 2009;23:632-9.

Functional impairment component of hoarding disorder (clutter)

The presence of an accumulation of possessions that congest and clutter active living areas is a useful criterion to differentiate clinical from normal hoarding. One assumption that is made in this definition is that clinically significant hoarding cannot occur in the absence of clutter. Although it is possible to imagine that someone could spend so much time acquiring, organizing, and protecting their possessions (and not cluttering their home) that they neglect other aspects of their lives, these cases are probably rare.¹¹11 . Frost RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. Behav Res Ther. 1996;34:341-50. However, the extent to which clutter may be present and/or interfere with usual activities may vary, and it is important to consider the different possibilities available in order to set the ideal threshold for a diagnosis of hoarding disorder.

Impossible use of living areas

The original definition of hoarding put forward by Frost & Hartl¹¹11 . Frost RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. Behav Res Ther. 1996;34:341-50. included the fact that living spaces had to be sufficiently cluttered so as to preclude activities for which those spaces were designed. Similarly, in a DSM-5 field trial, a particular criterion, requiring the clutter of hoarding disorder to result in an impossible use of living areas, was tested.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18. However, this alternative was considered too strict, as several individuals were significantly distressed and impaired and met all other diagnostic criteria for hoarding disorder, yet still managed to somehow use some of their “key” living spaces.

Difficult, but not impossible, use of living areas

A second option would require clutter to result in a substantially compromised use of active living areas. Arguably, this would achieve the right balance between false-positive and false-negative hoarding disorder cases. Although none of the non-pathological or benign “collectors” assessed in the DSM-5 hoarding disorder field trial (n=20) fulfilled the criterion before these proposed adjustments, lowering the diagnostic threshold did not lead to any additional diagnosis of hoarding disorder in this studied sample, thus suggesting that this alternative cannot be misused to pathologize normative human activity.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18.

One needs also to consider, however, that clutter may be absent among some patients with hoarding disorder if there is a history of recent decluttering by family members, cleaners, or authorities. In these cases, the diagnosis of hoarding disorder would be performed exclusively on the basis of cognitive and behavioral features leading to distress or impairment.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18. This alternative, which was also tested and adopted in DSM-5, would not exclude the possibility of adopting any of the diagnostic options for clutter described above.

Additional diagnostic features

In DSM-5, symptoms must result in clinically significant distress or impairment in different areas of functioning (including maintaining a safe environment). In ICD-11, functional impairment will not be strictly required for a diagnosis of a mental disorder (including hoarding disorder), although clinicians may use it as additional information to rate severity of symptoms.⁶⁵65 . International Advisory Group for the Revision of ICD-10 Mental and Behavioural Disorders. A conceptual framework for the revision of the ICD-10 classification of mental and behavioural disorders. World Psychiatry. 2011;10:86-92. In the opinion of the Working Group, the ICD-11 should also recognize that hoarding symptoms might be seen in a range of medical conditions (e.g., brain injury) and mental disorders (e.g., OCD). It also needs to state explicitly that, for a diagnosis of hoarding disorder, hoarding symptoms must not be better understood as a symptom of these conditions. It can sometimes can be difficult to differentiate hoarding disorder in association (comorbidity) with a specific disorder (e.g., OCD) from hoarding as a symptom of the same disorder. Theoretically, it is also possible that both situations could coexist in the same patient, thus adding further complexity to the diagnostic process.

Potential specifiers

Excessive acquisition

As described above, traditional conceptualizations of hoarding have listed excessive acquisition, inability to discard, and clutter as its key symptoms. In DSM-5, however, difficult discarding and clutter are the core features of hoarding. In that manual, excessive acquisition was included as a specifier that is not present in all patients with hoarding, but that is important to consider from a therapeutic point of view. It has been suggested that some patients with hoarding disorder who deny excessive acquisition may “acquire” possessions passively, simply allowing their homes to fill up naturally, with the habitual flow of mail, newspapers, and packaging from purchased products.

It may be difficult to differentiate the behavior exhibited by a subject who actively acquires possessions from that of an individual who passively lets objects accumulate day after day. Both behaviors may be intentional and serve the same purpose. For instance, consider the case of a hoarding disorder patient who, in response to sales calls, signs up for several different year-long newspaper subscriptions and thereafter starts receiving them daily at his door. Although no one will argue with a diagnosis of hoarding for this patient, it might be difficult to determine whether his hoarding disorder is associated with active or passive excessive acquisition.

As reported above, there is increasing recognition that almost all patients with hoarding have current or lifetime histories of excessive acquisition urges and/or behaviors, and that those who report otherwise may be avoiding buying- or other excessive acquisition-related cues or have low levels of insight into their behaviors.⁸⁶86 . Frost RO, Tolin DF, Steketee G, Fitch KE, Selbo-Bruns A. Excessive acquisition in hoarding. J Anxiety Disord. 2009;23:632-9. In addition, all studies describing a subset of patients without excessive acquisition relied on self-report assessments and did not include face-to-face interviews with clinicians focusing on excessive acquisition behaviors.⁶³63 . Timpano KR, Exner C, Glaesmer H, Rief W, Keshaviah A, Brähler E, et al. The epidemiology of the proposed DSM-5 hoarding disorder: exploration of the acquisition specifier, associated features, and distress. J Clin Psychiatry. 2011;72:780-6; quiz 878-9.,⁸⁵85 . Frost RO, Rosenfield E, Steketee G, Tolin DF. An examination of excessive acquisition in hoarding disorder. J Obsessive Compuls Relat Disord. 2013;2:338-345.,⁸⁶86 . Frost RO, Tolin DF, Steketee G, Fitch KE, Selbo-Bruns A. Excessive acquisition in hoarding. J Anxiety Disord. 2009;23:632-9. In the DSM-5 hoarding disorder field trial, up to 100% of subjects with hoarding disorder assessed by a trained interviewer exhibited excessive acquisition.⁵²52 . Mataix-Cols D, Pertusa A. Annual research review: hoarding disorder: potential benefits and pitfalls of a new mental disorder. J Child Psychol Psychiatry. 2012;53:608-18.

Taken together, these findings suggest that excessive acquisition is likely to be an integral part of hoarding disorder. Statistical analysis using a composite of interviews and self-report instruments has shown that the active acquisition of items, buildup of clutter, and difficulty discarding accumulated possessions co-occur strongly enough to be considered a unidimensional construct and are better conceived as part of a “cohesive hoarding phenotype.”⁸⁷87 . Meyer JF, Frost RO, Brown TA, Steketee G, Tolin DF. A Multitrait-Multimethod Matrix Investigation of Hoarding. J Obsessive Compuls Relat Disord. 2013;2:273-80. In this scenario, considering excessive acquisition as a mere specifier may overshadow its prevalence and therapeutic relevance among individuals with hoarding. A critical analysis of the available evidence suggests that excessive acquisition should be considered a core symptom of hoarding disorder.

Insight

In DSM-5, all OCRD with a cognitive component - OCD, hoarding disorder, and body dysmorphic disorder (BDD) - have an “insight” specifier for rating patients' insight into their disorder-related beliefs. For example, while some patients with OCD acknowledge that they will not be contaminated by HIV if touching doorknobs (good or fair insight), others may believe that they probably will get contaminated (poor insight), and others still may be absolutely convinced that they will get contaminated (absent insight). By adding a specifier to these conditions, the DSM-5 called attention to clinicians that patients with absent insight in the context of OCD or BDD do not need to receive an additional diagnosis of delusional disorder not otherwise specified.

Nevertheless, research has demonstrated that there are more similarities than differences between good- and poor-insight OCD⁸⁸88 . Fontenelle JM, Santana Lda S, Lessa Lda R, Victoria MS, Mendlowicz MV, Fontenelle LF. [The concept of insight in patients with obsessive-compulsive disorder]. Rev Bras Psiquiatr. 2010;32:77-82. and BDD.⁸⁹89 . Phillips KA, Hart AS, Simpson HB, Stein DJ. Delusional versus nondelusional body dysmorphic disorder: recommendations for DSM-5. CNS Spectr. 2014;19:10-20. Although adding motivational techniques may help ambivalent patients with both conditions, this categorization does not seem to impact, for instance, biological treatment, as all patients with OCD or BDD, regardless of insight level, should be treated with serotonin reuptake inhibitors rather than antipsychotic monotherapy. Furthermore, motivational therapy may be important in the treatment of severe OCD in general, regardless of whether it is associated with poor insight.⁹⁰90 . Meyer E, Souza F, Heldt E, Knapp P, Cordioli A, Shavitt RG, et al. A randomized clinical trial to examine enhancing cognitive-behavioral group therapy for obsessive-compulsive disorder with motivational interviewing and thought mapping. Behav Cogn Psychother. 2010;38:319-36.,⁹¹91 . Meyer E, Shavitt RG, Leukefeld C, Heldt E, Souza FP, Knapp P, et al. Adding motivational interviewing and thought mapping to cognitive-behavioral group therapy: results from a randomized clinical trial. Rev Bras Psiquiatr. 2010;32:20-9.

Although there is no study comparing poor- and good-insight hoarding disorder in terms of sociodemographic, clinical, or treatment outcomes, the same rationale regarding OCD and BDD is potentially applicable to it. However, an additional problem might exist. While poor insight is a frequent phenomenon among patients with hoarding disorder,⁹²92 . Tolin D, Fitch K, Frost R, Steketee G. Family informants' perceptions of insight in compulsive hoarding. Cogn Ther Res. 2010;34:69-81. the concept of poor insight into hoarding may be quite heterogeneous and potentially difficult for a general practice clinician to understand.⁵³53 . Saxena S, Brody AL, Maidment KM, Baxter LR Jr. Paroxetine treatment of compulsive hoarding. J Psychiatr Res. 2007;41:481-7. It can include, for instance, anosognosia (denial of illness), indifference to the consequences of hoarding behaviors, inflexible beliefs in relation to possessions, or even defensive reactions against change.

Despite these problematic conceptual issues, specifying the degree of insight into hoarding may have clinical utility. As suggested above, adopting this poor insight specifier would strength the ties between OCRD associated with a cognitive component (OCD, BDD, and hoarding disorder). Furthermore, if criteria are clearly operationalized, even the non-specialist can refer to poor insight in relation to at least two key hoarding elements, i.e., hoarding-related cognitions and/or behaviors, with a reasonable degree of confidence. By reminding clinicians that it is possible to diagnose hoarding disorder with poor insight in the absence of delusional disorder, clinicians may spare patients with hoarding disorder from being treated with antipsychotic monotherapy.

Severe domestic squalor

Hoarding and squalor have some significant areas of overlap, but the accumulation of objects does not necessarily lead to surroundings becoming unclean, and squalor can be observed in the absence of an accumulation of apparently worthless items and materials.⁹³93 . Snowdon J, Pertusa A, Mataix-Cols D. On hoarding and squalor: a few considerations for DSM-5. Depress Anxiety. 2012;29:417-24. So-called severe domestic squalor has been defined as “(A person's home) so unclean, messy, and unhygienic that people of similar culture and background would consider extensive clearing and cleaning to be essential. Accumulated dirt, grime, and waste material extend throughout living areas of the dwelling, along with possible evidence of insects and other vermin. Rotting food, excrement, and certain odors may cause feelings of revulsions among visitors. As well as accumulation of waste, there may have been purposeful collection and/or retention of items to such a degree that it interferes with occupant's ability to adequately clean up the dwelling.”⁹⁴94 . Snowdon J, Halliday G, Banerjee S. Definition and description of severe domestic squalor In: Snowdon J, Halliday G, Banerjee S, editors. Severe domestic squalor. Cambridge: Cambridge University Press; 2012. p. 1-15.

While approximately 10 to 20% of patients who participate in hoarding research studies may live in varying degrees of domestic squalor, the preponderance of such cases among individuals who require social services may be much higher.⁹⁵95 . Mataix-Cols D. Hoarding and severe domestic squalor. In: Snowdon J, Halliday G, Banerjee S, editors. Severe domestic squalor. Cambridge: Cambridge University Press; 2012. p. 65-80. However, it has been suggested that, currently, “there is no definite evidence that those with hoarding disorder who live in squalor have a condition that differs from hoarding disorder without squalor.”⁹³93 . Snowdon J, Pertusa A, Mataix-Cols D. On hoarding and squalor: a few considerations for DSM-5. Depress Anxiety. 2012;29:417-24. This observation was based on the fact that, at present, it is not possible to ascertain whether squalor is a mere consequence of severe hoarding or a marker of a specific subgroup of patients with marked neuropsychological dysfunction which may require different diagnostic procedures (e.g., neuropsychological assessment) and perhaps even different approaches (e.g., cognitive rehabilitation).⁹³93 . Snowdon J, Pertusa A, Mataix-Cols D. On hoarding and squalor: a few considerations for DSM-5. Depress Anxiety. 2012;29:417-24.,⁹⁵95 . Mataix-Cols D. Hoarding and severe domestic squalor. In: Snowdon J, Halliday G, Banerjee S, editors. Severe domestic squalor. Cambridge: Cambridge University Press; 2012. p. 65-80.

However, the ICD-11 Working Group believes that there are also some reasons to consider including squalor as a subtype of hoarding disorder in ICD-11. Firstly, hoarding with squalor may be associated with greater public health implications (including the presence of mosquitoes, rodents, vermin, infestations, excreta, pathogens, fire hazards, and sewerage problems) and justify early intervention from third parties, thus requiring prompt identification.⁹⁶96 . Snowdon J, Halliday G, Banerjee S. How best to intervene in cases of severe domestic squalor. In: Snowdon J, Halliday G, Banerjee S, editors. Severe domestic squalor. Cambridge: Cambridge University Press; 2012. p. 36-64. Considering that ICD-11 focuses on public health issues, it might be worthwhile to include squalor as a hoarding disorder specifier.

Secondly, squalor in cases of hoarding may be indicative of executive impairment and greater frontal lobe pathology than in hoarding without squalor, which would make it a marker of different pathophysiological events. Although there is no data to confirm this hypothesis, it has been demonstrated that patients with hoarding and squalor exhibit a wide range of comorbid psychiatric disorders that have been associated with executive dysfunction.⁹⁷97 . Snowdon J, Halliday G. A study of severe domestic squalor: 173 cases referred to an old age psychiatry service. Int Psychogeriatr. 2011;23:308-14. In light of this, squalor should prompt clinicians to search for comorbid conditions and make sure that dementia, alcohol-related, and psychotic disorders do not explain hoarding and squalor before a diagnosis of hoarding disorder is made.⁹⁷97 . Snowdon J, Halliday G. A study of severe domestic squalor: 173 cases referred to an old age psychiatry service. Int Psychogeriatr. 2011;23:308-14. Finally, in the absence of these severe neuropsychiatric disorders, hoarding disorder with squalor may be a potential prodrome, heralding the appearance of one of these severe neuropsychiatric disorders, and thus demand close follow-up.⁹⁵95 . Mataix-Cols D. Hoarding and severe domestic squalor. In: Snowdon J, Halliday G, Banerjee S, editors. Severe domestic squalor. Cambridge: Cambridge University Press; 2012. p. 65-80.

Animal hoarding

A phenomenon that has an intricate relationship with severe domestic squalor is the pathological accumulation of animals. Animal hoarding was first described more than 30 years ago,⁹⁸98 . Worth D, Beck AM. Multiple ownership of animals in New York City. Trans Stud Coll Physicians Phila. 1981;3:280-300. but was only recently defined in the public health literature⁹⁹99 . HARC. The hoarding of Animals Research Consortium [Internet]. 2013 [cited 2013 Jun 6]. http://vet.tufts.edu/hoarding/index.html
http://vet.tufts.edu/hoarding/index.html... as (i) having more than the typical number of companion animals, (ii) failing to provide even minimal standards of nutrition, sanitation, shelter, and veterinary care, with this neglect often resulting in illness and death from starvation, spread of infectious disease, and untreated injury or medical condition, (iii) denying the inability to provide this minimum care and the impact of that failure on the animals, the household, and human occupants of the dwelling, and (iv) persisting, despite this failure, in accumulating and controlling animals.

Some have argued that the profound attachment to hoarded animals, “which is often intertwined with a sense of mission to rescue animals,” has qualitative differences from the attachment patients with object hoarding have toward “their most dearly held inanimate possessions.”¹⁰⁰100 . Patronek GJ, Nathanson JN. A theoretical perspective to inform assessment and treatment strategies for animal hoarders. Clin Psychol Rev. 2009;29:274-81. Furthermore, it has been suggested that patients with animal hoarding may exhibit particularly high rates of dysfunctional personality traits and dissociative symptoms, which could, at least theoretically, explain their puzzling indifference to severe domestic squalor.¹⁰⁰100 . Patronek GJ, Nathanson JN. A theoretical perspective to inform assessment and treatment strategies for animal hoarders. Clin Psychol Rev. 2009;29:274-81. Animal hoarding seems to be more prevalent in women and to appear later than object hoarding, whereas object hoarding is probably more prevalent in men (reviewed by Frost et al.¹⁰¹101 . Frost RO, Patronek G, Rosenfield E. Comparison of object and animal hoarding. Depress Anxiety. 2011;28:885-91.). Finally, animal hoarding may lead to criminal prosecution, as most patients with animal hoarding have made a series of deliberate choices and acts, placing their interests above the interests of animals, and leading to foreseeable suffering and neglect.⁹⁹99 . HARC. The hoarding of Animals Research Consortium [Internet]. 2013 [cited 2013 Jun 6]. http://vet.tufts.edu/hoarding/index.html
http://vet.tufts.edu/hoarding/index.html...

In spite of its peculiarities, animal hoarding also overlaps extensively with object hoarding disorder. For instance, patients with animal hoarding also display difficulty discarding possessions, frequently refusing to give up sick, unnourished, or dying animals or even their carcasses.¹⁰²102 . Patronek GJ. Hoarding of animals: an under-recognized public health problem in a difficult-to-study population. Public Health Rep. 1999;114:81-7. Like object hoarders, animal hoarders may acquire animals through a variety of active and passive means.¹⁰³103 . Patronek G, Loar L, Nathanson JN. Animal hoarding: strategies for interdisciplinary interventions to help people, animals, and communities at risk. Boston: Hoarding of Animals Research Consortium; 2006. As it is possible to note from the above-mentioned definition, the concept of animal hoarding has some overlap with severe domestic squalor, insofar as animal hoarding cannot be present without some degree of squalor, although domestic filthiness does not necessarily include animal hoarding. For instance, virtually all homes in which animals are hoarded have their living areas contaminated with animal feces and urine.¹⁰⁰100 . Patronek GJ, Nathanson JN. A theoretical perspective to inform assessment and treatment strategies for animal hoarders. Clin Psychol Rev. 2009;29:274-81.,¹⁰²102 . Patronek GJ. Hoarding of animals: an under-recognized public health problem in a difficult-to-study population. Public Health Rep. 1999;114:81-7. Therefore, animal hoarding could be addressed within severe domestic squalor. Although there seem to be some particularities related to animal hoarding as compared with the traditional concept of object hoarding,¹⁰¹101 . Frost RO, Patronek G, Rosenfield E. Comparison of object and animal hoarding. Depress Anxiety. 2011;28:885-91. the evidence base is still too scarce to provide a definitive answer with regard to the status of this phenomenon.

Differential diagnosis of hoarding disorder in the ICD-11

As exemplified above, differential diagnosis of hoarding disorder with OCD can be difficult. In contrast to hoarding disorder, object accumulation in OCD (in this case, so-called compulsive hoarding) results from prototypical obsessions with aggressive (e.g., fear of harming others), sexual/religious (e.g., fear of committing blasphemous or disrespectful acts), contamination (e.g., fear of spreading infectious diseases), or symmetry/ordering themes (e.g., a feeling of incompleteness). In addition, even in poor-insight OCD, behaviors are generally unwanted and distressing, and are thus not associated with pleasure or enjoyment.

In major depressive disorder, decreased energy, lack of initiative, or apathy may lead to object accumulation. However, in contrast to major depressive disorder, saving of possessions in hoarding disorder is a purposeful and intentional behavior. Patients with major depressive disorder may also be indifferent to hoarding objects and display no distress associated with discarding them.

In bipolar disorder, object accumulation may be secondary to excessive buying, and thus restricted to manic episodes. However, difficulty discarding or parting with possessions is not part of the core symptoms of bipolar disorder. Furthermore, only very rarely is mania chronic enough to allow for a substantial amount of clutter to develop.

In schizophrenia and other primary psychotic disorders, object accumulation is driven by delusions, which are typically not accompanied by pleasure or enjoyment. In ambiguous cases, the presence of first-rank or/and negative symptoms may help establish a diagnosis of schizophrenia or schizophrenia-related condition. In addition, the content of a symptom in delusional disorders is generally restricted to a small number of themes, which are typically different from those reported in hoarding disorder.

In dementia, object accumulation may result from cognitive deficits, but there is typically no interest in accumulating objects or distress associated with discarding items. Furthermore, collecting behavior in dementia may be accompanied by severe personality and behavioral changes, such as apathy, excessive gambling, sexual indiscretions, and motor stereotypies.

In paraphilias, sexual fantasies, urges, or behaviors may result in object accumulation that are associated with pleasure or enjoyment and increased emotional attachment to the hoarded items. However, in contrast to hoarding disorder, object accumulation in paraphilia-related disorders is strictly related to sexual gratification.

In eating disorders (including the binging and/purging subtypes of anorexia nervosa, bulimia nervosa, and binge eating disorder), individuals may accumulate food to allow binge eating in specific situations (e.g., while at home alone). However, in contrast to hoarding disorder, the ultimate aim of object accumulation in eating disorders is the consumption of food.

In autism spectrum disorders, restricted interests may result in object accumulation, which may resemble that of hoarding disorder. However, patients with autism spectrum disorders display a number of additional features that are typically lacking among patients with hoarding disorder, including persistent deficits in social communication and social interaction.

In substance use disorders, individuals may be too impaired to declutter, and often live in squalor with accumulation of trash. In these cases, however, accumulation is secondary to the substance use disorder.

Prader-Willi syndrome is a genetic disorder that has been associated with increased drive to eat and a range of compulsive and ritualistic symptoms, including food storing. The presence of short stature, hypogonadism, failure to thrive, hypotonia, and a history of feeding difficulty in the neonatal period are helpful to distinguish Prader-Willi syndrome from hoarding disorder.

Individuals with hoarding disorder and animal hoarding need to be differentiated from “animal exploiters,” who breed and/or actively acquire animals for their own financial gratification. Animal exploiters usually display concomitant antisocial or borderline personality disorders or traits. They keep animals in poor conditions because they have no empathy regarding their suffering and do not care about them. It has been suggested that, when offered enough incentive, such individuals would dispose of their animals.⁹⁹99 . HARC. The hoarding of Animals Research Consortium [Internet]. 2013 [cited 2013 Jun 6]. http://vet.tufts.edu/hoarding/index.html
http://vet.tufts.edu/hoarding/index.html...

Conclusions

Despite the long-held view that hoarding was almost synonymous with OCD and/or OCPD, evidence has emerged during the last 20 years suggesting that hoarding disorder represents a distinct condition. While ICD-10 did not mention hoarding, DSM-IV-TR implicitly described it as a symptom of OCD, when severe, or of OCPD, when milder. Recently, DSM-5 recognized the distinctiveness of hoarding disorder as a discrete diagnostic entity within the chapter of OCRD. Considering the evidence supporting the clinical utility, global applicability, and appropriateness outside specialty mental health settings of hoarding disorder as an entity and the desirable harmonization of ICD-11 and DSM-5, it is the Working Group's opinion that hoarding disorder should also be included in ICD-11, specifically in the chapter on OCRD.

The Working Group tentatively defines hoarding disorder as an excessive attachment to a large number of possessions, regardless of their actual value, resulting in excessive acquisition of and failure to discard them, such that living spaces become cluttered and the use of active living areas compromised. Regarding specifiers, a number of issues should be taken into consideration. Excessive acquisition is probably too common among individuals with hoarding disorder to be considered a specifier. In fact, current evidence suggests it is an intrinsic part of the hoarding disorder phenotype.

The Working Group recommends the adoption of a poor-insight specifier in ICD-11 hoarding disorder diagnostic guidelines. It also suggests that severe domestic squalor should be considered as a specifier, especially in light of its ease of detection and its potential threat to community health as a whole. This latter suggestion is particularly relevant if one considers that the foundation of ICD-11 should be pertinence to primary care and public health, and not only to mortality/morbidity, clinical care, and research. Following the same line of reasoning, with a consideration of public health issues, one may consider animal hoarding within domestic squalor.

Acknowledgements

The Department of Mental Health and Substance Abuse, World Health Organization, has received direct support that contributed to the activities of the Working Group from several sources: the International Union of Psychological Science, the National Institute of Mental Health (USA), the World Psychiatric Association, the Spanish Foundation of Psychiatry and Mental Health (Spain), and the Santander Bank UAM/UNAM endowed Chair for Psychiatry (Spain/Mexico).

References

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