Gail Steketee, PhD

 in 2000, we were just beginning our study of this poorly understood behavior.

 Since then, hoarding disorder (HD) has been a subject of considerable research and has become an official diagnosis in DSM-5. DSM-5 criteria for HD do not specify the types of possessions that are necessary for this diagnosis. Because animals are legally considered property (ie, possessions), the hoarding of animals would appear to qualify as HD, although this question is not yet resolved in the psychiatric literature.

In light of this development, a review of the existing literature and a new look at animal hoarding is warranted. In this article, we provide an overview of what we have learned in the past 15 years about this behavior with respect to phenomenology, etiology, and treatment. At the outset, it is important to note that our knowledge of this condition is based on a limited number of studies. Consequently, what is described here should be viewed as a set of working hypotheses.

Although animal hoarding technically fits the criteria for HD, DSM-5 fell short of listing it as an official subtype, and Mataix-Cols

 has rightly noted that its diagnostic classification remains unclear on the basis of the available evidence. DSM-5 describes animal hoarding as a condition associated with HD and defined by “the accumulation of a large number of animals and a failure to provide minimal standards of nutrition, sanitation, and veterinary care and to act on the deteriorating condition of the animals (eg, disease, starvation, death) and the environment (eg, severe overcrowding, extremely unsanitary conditions).” Estimates from surveys of animal control agencies and humane societies suggest that there are approximately 3000 reportable cases of animal hoarding annually in the US.

The most dramatic feature of this behavior is the effect it has on the home environment. Large numbers of animals, often sick, dying, or dead, are crammed into living areas of the hoarder’s home. Often urine and feces cover the floors and/or walls, creating high concentrations of ammonia and aerosolized organic contaminants that pose serious health risks to occupants.

 In a study of complaints to health departments, animal hoarding was found to result in significantly more unsanitary conditions than did object hoarding and posed significantly more threat to the health of human occupants of the home and to the community at large.

 Surveys of caseworkers dealing with this problem indicate that a lack of appropriate sanitation appears in 70% to more than 90% of animal-hoarding cases, and together with the large number of animals involved, increases the likelihood of zoonotic diseases for the occupants and the community.

Case reports indicate that between 31% and 100% of individuals who hoard animals also hoard inanimate possessions.

 In these cases, the clutter and unsanitary conditions severely interfere with normal activities of daily living, such as sleeping in a bed, bathing, finding important objects, and preparing food. Often major appliances, toilets, showers, and tubs are not in working order. Inability to care for the hoarded animals and to maintain basic personal hygiene make this a problem of animal abuse as well as of the hoarder’s self-neglect. From a resource perspective, animal-hoarding cases require more agency involvement for resolution than do object-hoarding cases, and legal proceedings can result in substantial costs.

 have suggested 3 ways to classify persons who hoard animals: overwhelmed caregivers, rescuers, and exploiters. The overwhelmed caregiver is an individual who owns a large number of animals that were reasonably well cared for until a change in circumstances impaired the individual’s ability to provide proper care for them. Most often, the circumstances involve loss of resources, such as death of a spouse, loss of a job, or failing health. These individuals often initially make attempts to provide adequate care but eventually become overwhelmed, and living conditions deteriorate. Their acquisition of animals tends to be passive, with new animals coming from breeding among the animals they have. Overwhelmed caregivers of-ten exhibit some awareness of their problems with animal care and tend to minimize rather than deny them. Isolation may be a factor in their reluctance to seek help. When they are confronted by authorities, they have fewer problems complying with intervention than rescuers or exploiters.

A strong sense of mission to save animals from a presumed threat characterizes the more serious rescuers or those who are mission-driven. These individuals vehemently oppose euthanasia and show strong fears about the death of their animals, even though they fail to recognize the poor quality of the care they are providing. They believe only they can adequately care for their animals. Even as they become overwhelmed, they continue to collect new animals, often relying on a large network of enablers who facilitate their acquisition of more animals. Their acquisition methods tend to be more active than passive, often involving going in search of animals they perceive to be in need of rescue. Mission-driven animal hoarders or rescuers go to great lengths to avoid authorities and actively prevent outside influence over their growing population. These individuals now often present themselves as organized institutional personnel, often masquerading as representatives of a legitimate shelter or sanctuary that cares for hundreds of animals.

Animal-hoarding cases typified by exploiters are the most serious and difficult to resolve. They involve individuals with sociopathic characteristics who acquire animals to serve their own needs, with little true attachment to them. These individuals appear indifferent to the suffering of their animals, and they lack empathy for humans and animals. They display extreme denial of any problems and flatly reject authority or any outsider’s legitimate concerns. As do the mission-driven animal hoarders, exploiters believe their knowledge is superior to anyone else’s, and they display an extreme need to exert control over their animals. Exploiters display many characteristics of antisocial personality disorder, including superficial charm and charisma; they are manipulative and cunning, narcissistic, and appear to lack guilt or remorse. The absence of emotional attachment to their animals suggests that these individuals may not fit the diagnostic criteria for HD.

Very little research has been done to verify these classifications of animal hoarding. However, in a review of a small number of cases, Reinisch

 classified 40% as overwhelmed caregivers, 20% as mission-driven hoarders, and 40% as exploiters.

Typical characteristics ofanimal hoarders

The majority of studies that examined the phenomenology of animal hoarding are detailed case reports prepared by animal control agencies and humane societies. In the two largest reports, the findings regarding sex and age were remarkably similar. Patronek

 reported that 76% of 54 hoarders were female, and nearly half of the 54 were 60 years or older. A report by the Hoarding of Animals Research Consortium (HARC) detailed 71 cases.7 Eighty-three percent of these cases were women; the average age was the mid-50s. Animal-hoarding behavior appears to develop in middle age or later, although research is lacking on this point.

 From half to nearly three-quarters of the individuals in these studies were single, widowed, or divorced. Interestingly, over half of the HARC sample lived with other individuals, including children and elders. Smaller case studies have reported similar sex and age distributions

; a recent Spanish study found a similar age distribution but a more equal sex representation.

Most of the few studies on animal hoarding outside North America are case studies that document the existence of animal hoarding or describe the characteristics of hoarders within particular countries. For example, Svanberg

 reported media and government reaction to a Swedish woman who “rescued” 150 swans over several years by bringing up to 10 at a time to her one-room apartment. Also in Sweden, Zak

described the case of a hoarder with 80 dogs, 1 cow, 2 pigs, 1 rabbit, and some poultry in unsatisfactory conditions, without any veterinary care. Other studies have detailed the condition of animals and characteristics of the owners in Spain, New South Wales, and Serbia

; these reports were similar to those from the US.

As noted, a recent study by Ockenden and colleagues

 in Australia found demographic similarities with US animal-hoarding cases, but the affected animals were in better condition than their American counterparts. To provide insight into the development of animal hoarding, Ramos and colleagues

 examined Brazilians who own large numbers of animals that are adequately cared for in normally functioning homes. These individuals showed more intense attachments to their pets than owners of just 1 or 2 animals; these types of attachments were suggested to be precursors to animal hoarding.

Types of animals most likelyto be hoarded

Details regarding the number and kinds of hoarded animals generally have been consistent across studies. Cats are the most frequently reported type of animal hoarded, followed by dogs, although in a study from Spain, there was a higher frequency of dogs than cats among the animal-hoarding cases.

 Farm animals and birds were also reported with some frequency (11% to 17% in some studies20). In the study by Patronek,

 in 35% of the cases, only a single species was hoarded; in 31% of the cases, 2 species were hoarded; and in 33% of the cases, more than 2 species were hoarded. Calvo and colleagues

 reported that 79% of cases involved a single species. The typical number of animals in these cases ranged from 10 to more than 900. Women were more likely than men to have more than 100 animals, and middle-aged persons (aged 50 to 64 years) had significantly more animals than did those who were younger or older.

A comparison of animal and object hoarding outlined similarities, including a chronic course characterized by an exaggerated need to control, an exaggerated sense of responsibility, and intense emotional attachments to hoarded objects or animals.

 Both types of hoarding are also characterized by poor insight and great difficulty in parting with objects or animals. In both object hoarding and animal hoarding, the urge to save/acquire is intense, as is the distress when possessions are removed. A result of these behaviors is a seriously compromised living environment; in most cases, hoarding of animals results in more severe personal and public health consequences.

There are some notable differences between object and animal hoarding. In one study, most animal-hoarding cases involved squalid living conditions, while only a minority of object-hoarding cases did so.

 A review of the sex ratio indicates that it is relatively even for object hoarding, whereas animal hoarders are predominantly female.

 Although both conditions are characterized by poor insight, animal hoarders often exhibit delusional beliefs about special abilities to communicate with, understand, and care for animals.

There is little documentation of the clinical trajectory of animal hoarding, although anecdotal reports are available and one book provides an in-depth self-report.

 examined the characteristics and antecedents of hoarding behaviors by interviewing 16 individuals who fit the criteria for animal hoarding and 11 individuals who owned many animals but did not meet hoarding criteria. Both groups comprised mainly white, middle-aged women who owned an average of 31 animals. Interestingly, individuals in both the hoarding and nonhoarding groups reported stressful childhood and adult life events as well as strong feelings about animals, such as urges to rescue, take care of, and be close to them. However, those who hoarded animals more often attributed human characteristics to animals and reported having had more problems with early attachments to caregivers and chaotic childhood environments. They also had more dysfunctional current relationships and mental health concerns. This report and clinical impressions suggest the following recurring themes among individuals with animal-hoarding disorder:

• Unshakable belief that they are saving, rescuing, or caring for their animals, which they see as being well and happy

• Profound compulsion to maintain or increase the collection of animals despite ample evidence of their failure to provide adequate care

• Childhood history of parents who were unstable, neglectful, abusive, absent, and/or inconsistent, often with chaotic, transient lifestyles

• Difficulty in establishing and maintaining stable interpersonal relationships as an adult

• Trauma in childhood and/or adulthood: often multiple, severe traumatic events, such as sexual abuse or assault, parental abandonment, or death or unexpected loss of loved ones

Unfortunately, there are no articles that describe the clinical characteristics of animal hoarders based on formal psychological/psychiatric evaluations. Nonetheless, these themes suggest that information about the human-animal bond may provide a starting point for understanding the development of animal-hoarding disorder.

 have proposed an attachment-based explanatory model. Consistent with this approach, a psychodynamic theory proposed by Brown

 suggests explanations for the underpinnings of a “normal” human-animal bond and shows how these concepts may be relevant when the bond goes awry, as occurs in animal hoarding. Brown grounds her theory in the well-established importance of attachment security during development and the knowledge that when needs are not met during this critical period, particularly when accompanied by trauma, disorders of the self and dysfunctional attachment styles can result.

Attachment to companion animals can be profound, even for nonhoarding pet owners. Individuals who hoard animals show difficulty in letting go of them, even after they are dead. Their attachments are rigid and extreme, frequently at the expense of the well-being of the animals. Brown suggests that in animal-hoarding disorder, companion animals provide critical self-object functions, even into adulthood. Accordingly, reliance on an animal(s) can become intense and crucial to a person’s sense of well-being, with loss or potential loss of the animal(s) creating a sense of fragmentation, disintegration, and depression.

Many aspects of Brown’s hypothesis are also consistent with Flores’s

 framing of addiction as having its roots in attachment disorder, whereby the addictive behavior represents attempts at self-repair. Indeed, in “People Who Hoard Animals,” similarities in animal hoarding and addictive behavior were noted.

 The powerful positive feedback persons with animal-hoarding disorder may receive from their imagined role as animal caregiver is consistent with this approach and may explain what drives the hoarding behavior.

Building on this work, Patronek and Weiss

 explored the application of Allen and Fonagy’s

 work on mentalization theory as a way to further understand the various features of animal hoarding. Mentalization has been described as a form of emotional knowledge that involves being able to appreciate the reality of others and as a dynamic skill that is compromised by intense emotions associated with attachment relationships.

 describes how adults with a history of childhood attachment trauma fail to understand how others (people and animals) think and feel. Impaired mentalization may be one mechanism that helps maintain hoarding behavior.

 Although problems in mentalization in persons with animal-hoarding disorder remain to be examined, the possibility of deficits in this area has important implications for therapy.

Research in other spheres may play a crucial role in the developing science of animal hoarding. For example, complex feedback mechanisms involving the oxytocinergic system have been linked not only to a history of childhood adversity but also to human-animal interactions.

 Oxytocin may promote a tendency to “tend and befriend” animals and increase defensive behavior against perceived threats from outsiders. Tending and befriending is a more typical response to stress among women than men, which would be consistent with the sex disparity seen in animal hoarding.

 While it is speculative, this account suggests avenues for neurobiolog-ical research into animal-hoarding disorder.

Animal hoarding poses some unique legal issues, above and beyond those typically encountered in extreme object hoarding, because the conditions observed in these cases often violate state criminal statutes prohibiting cruelty to animals. Unlike civil child protection laws, however, animal cruelty statutes do not provide an avenue for intervention until a crime can be proved. Thus, in the absence of voluntary cooperation or the presence of children or dependent adults whose welfare may be compromised, intervention may be delayed until environmental conditions deteriorate substantially. Ultimately, despite potential mental illness that contributes to the behavior, a person with animal-hoarding disorder may be prosecuted and subjected to criminal penalties, including fines, jail, and/or forcible removal of animals and/or prohibitions or limitations on future ownership or caregiving, with no provision for mental health treatment.

The animals are often in legal limbo for months to years during protracted legal proceedings because, under the law, they are treated primarily as evidence rather than as victims of a crime.

 There is also no legal mandate that the interests of the animals must be considered during case disposition. To avoid this, some agencies may not prosecute but, instead, may attempt to negotiate, even if the proposed solutions are suboptimal for animals and people.

Clinical evaluation of a person with animal-hoarding disorder can take 2 primary forms: psychiatric evaluation for purposes of therapy and forensic evaluation for the courts. For the former, we recommend that the clinician be skilled in evaluating a broad spectrum of behavioral disorders and familiar with published guidelines for assessing and treating object hoarding.

 Given the potential for deep attachment to animate beings who often provide reciprocal interaction, there may be limits to how far we can extrapolate from object hoarding. Thus, it is important for the therapist to be knowledgeable about the human-animal bond and to explore those issues with the individual.

 The potential for self-neglect should also be explored.

With respect to forensic evaluation, several dozen states have legislated mandatory or discretionary evaluation of persons convicted of animal maltreatment, including animal hoarding. However, legislatures provide little guidance on what the goals of such an evaluation might be (eg, detection of danger to public safety, detection of mental illness, identification of being dangerous to self and others, identification of competency/capacity to care for animals). Limited forensic instruments are available for these purposes, and none has yet been validated. (One such instrument has been used for several years at the University of Denver and will be described in an upcoming book by Levitt, Grisso, and Patronek.

Many studies of animal hoarding report recidivism rates from 60% to 100%.

 Recidivism in this context refers to the frequency with which people reacquire multiple animals after having animals legally removed. This differs from the concept of relapse, which refers to the return of symptoms after someone has been successfully treated for a disorder. Nothing is known about relapse in animal hoarding, since no studies of treatment outcomes have been done. However, there are some case examples of individuals who have stopped hoarding animals and have been able to keep from reacquiring them.

As noted earlier, although courts may mandate counseling, no validated therapy for animal-hoarding disorder is available. In addition, most individuals who have been adjudicated for animal hoarding are reluctant to participate in therapy, making this strategy difficult to enforce. Similar to nonvoluntary clients who are prosecuted in housing courts for object hoarding, the most appropriate method for initial engagement of persons with animal-hoarding disorder may be through community task forces composed of a mix of service professionals (housing, police, fire, public health, mental health, legal). Members of such multidisciplinary task forces can work together to engage offenders in identifying goals that matter to them while requiring compliance with nonhoarding behaviors. Of critical importance is determining whether to limit the number of animals or require abstinence (eg, because of overt cruelty rather than neglect).

Essential to this process is determining how to provide basic social support that meets the need for bonding that was previously filled by animals. According to Fonagy and colleagues,

 it is important that therapists avoid demanding a level of mentalizing from patients that is beyond their ability. A relatively high level of metacognition (ie, the ability to reflect on one’s own thought process or that of others) is required before a patient’s own distorted thinking can be challenged and distinguished from reality. Our clinical experience strongly suggests that animal hoarders often show profound deficits in this area.

Quick fixes for these cases are unlikely; court-mandated therapy must be applied carefully to avoid extending the period of legal limbo for animals or putting animals at future risk. Given the long-standing nature of the hypothesized psychopathology underlying animal hoarding, even in an ideal situation with a cooperative and receptive patient, a longer-term therapeutic undertaking with periodic checks on compliance would be expected.

Dr Frost is Harold and Elsa Siipola Israel Professor or Psychology at Smith College, Northampton, Mass. Dr Patronek is Adjunct Assistant Professor at the Cummings School of Veterinary Medicine, Tufts University, North Grafton, Mass. Dr Arluke is Professor of Sociology at Northeastern University, Boston. Dr Steketee is Professor in the School of Social Work at Boston University. The authors report no conflicts of interest concerning the subject matter of this article.

. 2000;17(4):25-29. http://www.psychiatrictimes.com/obsessive-compulsive-disorder/people-who-hoard-animals. Accessed March 7, 2015.

 Mataix-Cols D. Clinical practice. Hoarding disorder. 

 Patronek GJ. Animal hoarding: its roots and recognition. 

. August 1, 2006. http://veterinarymedicine.dvm360.com/animal-hoarding-its-roots-and-recognition. Accessed March 7, 2015.

 Patronek GJ. Hoarding of animals: an under-recognized public health problem in a difficult-to-study population. 

 Douwes J, Thorne P, Pearce N, Heederik D. Bioaerosol health effects and exposure assessment: progress and prospects. 

 Frost RO, Steketee G, Williams L. Hoarding: a community health problem. 

 Health implications of animal hoarding. 

 Steketee G, Gibson A, Frost RO, et al. Characteristics and antecedents of people who hoard animals: an exploratory comparative interview study. 

. 2011;15:114-124. http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=2011-09729-001. Accessed March 7, 2015.

 Patronek GJ, Loar L, Nathanson JN, eds. 

Animal Hoarding: Structuring Interdisciplinary Responses to Help People, Animals, and Communities at Risk.

 Hoarding of Animals Research Consortium. 2006. http://www.tufts.edu/vet/hoarding/pubs/AngellReport.pdf. Accessed March 7, 2015.

 Reinisch AI. Characteristics of six recent animal hoarding cases in Manitoba. 

 Frost RO, Patronek G, Rosenfield E. Comparison of object and animal hoarding. 

 Ockenden EM, De Groef B, Marston L. Animal hoarding in Victoria Australia: an exploratory study. 

 Worth D, Beck AM. Multiple ownership of animals in New York City. 

 Calvo P, Duarte C, Bowen J, et al. Characteristics of 24 cases of animal hoarding in Spain. 

 Svanberg I. The social construction of the swan lady: a case of animal hoarding in Sweden. Unpublished paper. Uppsala Centre for Russian and Eurasian Studies. 2011.

. April 22, 2014. http://www.theatlantic.com/health/archive/2014/04/does-your-dog-or-cat-actually-love-you/360784. Accessed March 7, 2015.

 Joffe M, O’Shannessy D, Dhand NK, et al. Characteristics of persons convicted for offences relating to animal hoarding in New South Wales. 

 Vucinic M, Radisavljevic K, Vukmirovic N. Some cases of animal hoarding from Serbia. In: Proceedings from the 21st International Conference on Animal Protection and Welfare; October 9, 2014; Brno, Czech Republic.

 Ramos D, da Cruz NO, Ellis SLH, et al. Early stage animal hoarders: are these owners of large numbers of adequately cared-for cats? 

 Berry C, Patronek GJ, Lockwood R. Animal hoarding: a study of 56 case outcomes. 

 Rasmussen JL, Steketee G, Frost RO, et al. Assessing squalor in hoarding: the Home Environment Index. 

 Steketee G, Frost RO. Phenomenology of hoarding. In: Frost RO, Steketee G, eds. 

. New York: Oxford University Press; 2014:19-32.

Stuff: Compulsive Hoarding and the Meaning of Things

. New York: Houghton Mifflin Harcourt. 2010:118-133.

Inside Animal Hoarding: The Case of Barbara Erickson and Her 552 Dogs

. West Lafayette, IN: Purdue University Press; 2009.

 Nathanson JN, Patronek GJ. Animal hoarding: how the semblance of a benevolent mission becomes actualized as egoism and cruelty. In: Oakley B, Knafo A, Madhavan G, Wilson DS, eds. 

. New York: Oxford University Press; 2012:107-115.

 Brown SE. The human-animal bond and self-psychology: toward a new understanding. 

 Brown SE. Companion animals as self-objects. 

 Brown SE. Theoretical concepts from self-psychology applied to animal hoarding. 

 Patronek GJ, Weiss KJ. Animal hoarding: a neglected problem at the intersection of psychiatry, veterinary medicine, and law. Findings from the Henderson House Workgroup. Poster presented at: American Psychology-Law Conference; 2012; San Juan, Puerto Rico. Poster 117-64. http://www.tufts.edu/vet/hoarding/pubs/APLS2012.pdf. Accessed March 7, 2015.

Handbook of Mentalization-Based Treatment

Mentalization-Based Treatment for Borderline Personality Disorder: A Practical Guide

. Oxford, UK: Oxford University Press; 2006.

 Fonagy P, Gergely G, Jurist E, Target M. 

Affect Regulation, Mentalization, and the Development of the Self

 Fonagy P, Target M. The mentalization-focused approach to self-pathology. 

 Allen JG. Mentalizing in practice. In: Allen JG, Fonagy P, eds. 

 Pierrehumbert B, Torrisi R, Laufer D, et al. Oxytocin response to an experimental psychosocial challenge in adults exposed to traumatic experiences during childhood or adolescence. 

 Miller SC, Kennedy C, DeVoe D, et al. An examination of changes in oxytocin levels in men and women before and after interaction with a bonded dog. 

 Taylor SE, Klein LC, Lewis BP, et al. Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight. 

 Bernstein M, Wolf BM. Time to feed the evidence: what to do with seized animals. 

. 2005;35:10679-10689. http://elr.info/sites/default/files/articles/35.10679.pdf. Accessed March 7, 2015.

 Patronek GJ, Nathanson JN. A theoretical perspective to inform assessment and treatment strategies for animal hoarders. 

Animal Maltreatment: Forensic Mental Health Issues and Evaluations

. New York: Oxford University Press. In press.

 Fonagy P, Bateman A, Bateman A. The widening scope of mentalizing: a discussion. 

 2011;84:98-110. DOI: 10.1111/j.2044-8341.2010.02005.x. Accessed March 7, 2015.

Articles

The authors provide information about the human-animal bond that may provide a starting point for understanding the development of animal-hoarding disorder.

The Hoarding of Animals: An Update

In North America, an estimated 30% of the population maintains a collection of some sort.

 The practice of collecting, in which individuals maintain collections of objects that are generally considered interesting and valuable is distinctly different from that of hoarding.

 Compulsive hoarding is characterized by the following criteria

• The acquisition of, and failure to discard, a large number of possessions

• Excessive clutter that precludes activities for which the living space was designed

• Significant distress or impairment in functioning caused by the hoarding

Hoarding has broad-reaching implications, including a substantial public health burden linked to occupational impairment, poor physical health, and demand for social services.

 For example, it is not uncommon for community public health departments to become overburdened with property complaints regarding unsanitary conditions and fire hazard risks, and the cost to address a problem (eg, repetitive clean-outs, repeated visits by health inspectors, multiple-agency involvement) is high.

 These costs have led to the establishment of community-wide task forces in a number of cities.

 However, efforts to reconcile the problem are often diminished by the relative unavailability or ineffectiveness of mental health services.

In addition to the effects of hoarding on the community, family dynamics are often strained.

 Substantial distress, frustration, hostility, and rejection of hoarders are not uncommon.

 In a recent online study of hoarding, more than half of the participants were described as having poor or no insight into the severity of their hoarding behaviors, and family members’ attitudes of rejection were correlated with less awareness of illness among those who hoard.

For the individual who hoards, outcomes may include substantial work impairment, eviction or threat of eviction, or having a child or elder removed from the home.

 In general, persons with hoarding problems seek treatment after age 40 years, although hoarding symptoms commonly begin in the early teenage years.

 Those who hoard tend to live alone and may have a family member (parent, sibling, older relative) with the problem.

The prevalence of clinically significant hoarding in the general population ranges from 2% to 5%, and between 6 million and 15 million persons in the United States are affected, according to recent epidemiological studies.

 Hoarding appears to affect more men than women, although women are more likely to participate in research and seek treatment.

Hoarding is a significant psychiatric problem that occurs at twice the rate of obsessive-compulsive disorder (OCD) and at almost 4 times the rate of bipolar disorder and schizophrenia.

 It has been linked with impulse control disorders and appears to have high comorbid rates of major depressive disorder (MDD), social anxiety disorder, generalized anxiety disorder (GAD), attention-deficit/hyperactivity disorder (ADHD), and personality disorders.

What is already known about hoarding? 
? Clinically significant hoarding affects between 6 million and 15 million persons in the United States, according to recent epidemiological studies, occurring at twice the rate of obsessive-compulsive disorder (OCD) and at 4 times the rate of bipolar disorder and schizophrenia. It appears that hoarding is accompanied by high rates of comorbidity. A number of self-report and clinician-administered hoarding-specific measures aid in the assessment of symptoms and severity. Treatment for hoarding is guided by a cognitive-behavioral therapy (CBT) approach.

What new information does this article provide? 
? Historically, hoarding has been deemed a subtype of OCD, although forthcoming evidence suggests there are more differences than similarities. Hoarding is under consideration for inclusion in DSM-5 as a stand-alone disorder. A set of provisional criteria for hoarding disorder has been proposed and will require further study in the future. A recent study conducted by Frost and colleagues that examined the largest sample of participants to date confirmed that major depressive disorder was the most frequently occurring comorbid condition (more than 50%) and that kleptomania was a factor in 10% of the sample. This article highlights treatment options for hoarding that are available to practitioners, including alternative approaches focusing on self-help, support group, and Web-based delivery models.

What are the implications for psychiatric practice? 
? Individually administered CBT, following the protocol developed by Steketee and Frost, appears to be the most effective treatment, with a 70% to 80% rate of clinical improvement for patients who complete treatment. Given the expense and limited availability of individual treatment, alternatives, including group CBT, Web-based treatment, in-person self-help groups, and in-home coaching assistance, may provide sustainable and affordable approaches to this significant societal problem. Further research to better understand hoarding and to provide additional cost and resource-sensitive solutions is ongoing.

Historically, hoarding has been considered a subtype of OCD, although recent evidence suggests that there are more differences than similarities.

 Studies of patients with OCD have shown an 18% to 40% frequency of hoarding in adults and children and adolescents, although, hoarding is identified as a major or primary symptom in fewer than 5% of cases.

 Early studies that support this finding were derived from measures that do not adequately assess the presence or severity of hoarding (ie, Yale-Brown Obsessive Compulsive Scale30).

 Recent studies have incorporated reliable and valid measures (eg, Saving Inventory-Revised [SI-R], Hoarding Rating Scale-Interview [HRS-I], Clutter Image Rating [CIR]) that assess specific symptoms of hoarding as well as changes in symptoms following treatment.

Comorbidity and implications for diagnosis

The identification of hoarding as a subtype of OCD has influenced scientific understanding of its comorbidity. Progressive research efforts have advanced the definition and measurement of hoarding, providing a more reliable diagnosis and assessment of comorbidity.

 A recent study by Frost and colleagues (R. O. Frost, G. Steketee, D. F. Tolin, K. Glossner, unpublished data, 2011) examined 217 hoarding participants, the largest sample to date, who were recruited to meet diagnostic criteria for hoarding disorder (HD) currently under review for DSM-5.

 The study confirmed that a minority of participants with HD (fewer than 20%) also had OCD diagnoses and that MDD was the most frequent comorbid condition (more than 50%). This was followed by GAD and social phobia in approximately 25% of HD participants.

The rates for posttraumatic stress disorder were relatively low (7%), but the HD sample was more likely than OCD patients to have experienced a traumatic event as an adult or as a child. This finding is consistent with earlier research about the frequency of traumatic events among those who hoard.

 Inattentive ADHD was significantly more frequent in hoarding than in OCD (30% vs 3%), which supports the speculation that attention deficits are relatively common among those who hoard, but certainly this is not a universal characteristic.

It is not surprising that compulsive buying and excessive acquiring of free things were common among the hoarding sample (about 60%), and even the prevalence of kleptomania was surprisingly high at 10% of the sample. These findings confirm recent reports that more than 80% of people with self-reported hoarding acquire excessively.

 Obsessive-compulsive personality disorder (OCPD) was the most frequent personality disorder found among hoarding participants, even when hoarding was omitted from the criteria for OCPD.

Today, hoarding is cited in DSM-IV-TR as one of the diagnostic criteria for OCPD and, when hoarding is deemed severe, a symptom of OCD.

Hoarding has been a core diagnostic criterion for OCPD only since DSM-III-R and as a possible OCD symptom within the differential diagnosis section OCPD since DSM-IV.

 Given the presumption that hoarding was a symptom of OCD, many studies have evolved from this assumption and have influenced clinical understanding of the disorder.

 More recently, however, growing evidence supports the separation of hoarding from OCD.

In the interest of clarifying the clinical phenomenon, increasing public awareness, improving identification of cases, and stimulating further research and development of effective treatments for hoarding, a set of provisional criteria has been proposed (

 These will require further study in the coming years.

The manifestations of hoarding (acquisition, difficulty with discarding, clutter), outlined in an emerging cognitive-behavioral model, are hypothesized to evolve from core vulnerabilities based on early life experiences, genetic predisposition, current mood state, and personality traits (

On the basis of this model, cognitive information processing deficits (focusing attention, decision making, organizing, and possibly perception) are thought to be persistent factors in generating hoarding. A combination of early experiences and cognitive challenges result in mistaken beliefs about and attachments to possessions, with resulting negative emotions that lead to avoidance behaviors (saving unneeded items) and clutter. In addition, objects that evoke feelings of positive attachment and experiences of pleasure may result in excessive acquiring and clutter.

The elements of mental health treatment for hoarding are based on the theoretical model for this multidimensional problem. The protocol uses a manualized cognitive-behavioral therapy (CBT) approach that incorporates assessment and goal setting, organizing and problem-solving skills training, exposure practice methods to reduce acquiring and remove clutter, and motivational interviewing to address patient resistance when it arises during treatment.

The tools to measure hoarding symptoms and severity include the SI-R, a 23-item self-report questionnaire that assesses difficulty with discarding, clutter, and excessive acquisition; a score of 41 or higher typically indicates a clinical hoarding problem.

 The HRS-I helps clinicians make a diagnostic assessment of the 5 main features of hoarding (clutter, acquisition, difficulty with discarding, distress, impairment), each rated on a 0 to 8 scale; the HRS-I can also be used as a self-report scale.

 The CIR is a pictorial measure of in-home clutter severity intended for use by patients, family members, clinicians, or independent assessors.

 The Saving Cognitions Inventory is a 24-item self-report measure of beliefs experienced by patients when they attempt to discard items; subscales of this measure include emotional attachment, concerns about memory, control over possessions, and responsibility toward possessions.

The most effective approach to date appears to be individually administered CBT, following the model and methods of Steketee and Frost.

 A recent pilot study of 10 completers and a controlled trial with 37 completers yielded rates of 70% improved or much improved according to the therapists and 80% according to patients. Overall, 60% of patients showed clinically significant improvement following 26 sessions of individual CBT that included monthly in-home visits.

 Group interventions that included 20 sessions of CBT were only slightly less effective and appear to offer considerable potential for cost-saving solutions.

Further research is necessary to examine methods to enhance cognitive function (eg, attention, executive functioning) to improve the effectiveness of CBT.

 Expanding study inclusion criteria to allow men and persons from other cultures, races, and socioeconomic status will help generate more information about outcomes and strategies appropriate for all persons who hoard.

Cost-saving, stepped-care strategies for delivering CBT

The delivery of in-person, individual or group therapy for hoarding depends on skilled clinicians trained to treat persons with this problem. Because individual and even group treatment can be expensive and unavailable to many individuals with this highly prevalent condition, alternative approaches have focused on the application of self-help bibliotherapy, online and in-person support groups, coaching, and Web-based CBT.

 describe a 2009 study undertaken by Pekareva-Kochergina and Frost. The researchers examined the benefits of a 13-week intervention during which 2 undergraduate students supervised by a senior clinician facilitated 2 self-help groups. Participants read Buried in Treasures: Help for Compulsive Hoarding,

 a book describing hoarding, and were encouraged to practice the strategies proposed. At the close of the group sessions, 41% of participants rated themselves “much improved.” This student-led group yielded a surprisingly positive outcome for group members in a relatively short period.

In 2010, a Web-based self-help group for hoarding, established in 1998, was studied by Muroff and colleagues.

 Members participated in online chats, accessed an archive of resources hosted on the Web site, and were required to post action steps and progress reports at least monthly. Both long-term and recent members showed reductions in clutter and hoarding symptoms over a 15-month period. More active participants on the Web site showed statistically lower levels of hoarding. This group represents an intervention model that holds the potential to economically extend treatment to a geographically dispersed group.

The benefit of in-home assistance by clinicians is time-consuming and costly. Muroff and colleagues8 introduced non-clinician, in-home assistants (trained undergraduate student coaches) into a hoarding treatment group to reinforce skills learned in group treatment and boost CBT-based outcomes for participants. Clinicians who led the group communicated with coaches through in-person and telephone group supervision and use of a system to track and docu-ment home visits throughout the 20-week treatment period. One group of participants received 4 home visits from one of the cotherapists, the second group received an additional 4 home visits from the undergraduate coaches. Although reductions in hoarding symptoms were not statistically significant, additional in-home assistance appeared to offer improved (albeit small) outcomes. Additional studies will help further define the effect of this enhancement to group treatment.

A pilot study is under way to test the feasibility, acceptability, and effectiveness of computer- and Webcam-delivered CBT for hoarding symptoms. Preliminary results show potential for a cost-effective, direct service solution to in-home locations where hoarding occurs.

 Initial outcomes of this 26-session, weekly home-based CBT treatment delivered via Webcam showed moderate improvement of participant’s hoarding symptoms and was administered over a 30- to 38-week period compared with an average 49 weeks of in-person treatment.

These stepped-care strategies demonstrate potential to assist a broader spectrum of patients using CBT hoarding interventions and offer a sustainable, economic approach to this societal problem. Given the large number of persons who hoard, the debilitating and potentially deadly consequences, and the sometimes limited insight into the severity of their symptoms, it seems essential to learn more about this complicated problem. Current CBT regimens are effective, but they are costly. Accordingly, more research is needed to better understand the disorder and to provide relief from this chronic problem.

On Collecting: An Investigation Into Collecting in the European Tradition.

Compulsive Hoarding and Acquiring: A Therapist Guide

. New York: Oxford University Press; 2007.


 Frost RO, Gross RC. The hoarding of possessions. 

 Frost, RO, Hartl TL. A cognitive-behavioral model of compulsive hoarding. 

 Tolin DF, Frost RO, Steketee G, et al. The economic and social burden of compulsive hoarding. 

 Steketee G, Frost R. Compulsive hoarding: current status of the research. 

 Hoarding has broad-reaching implications, including a substantial public health burden linked to occupational impairment, poor physical health, and demand for social services.

Author | Gail Steketee, PhD

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