Hoarding Disorder: Models, Interventions, and Efficacy

Hoarding has recently received a great deal of public attention, especially with the proliferation of reality TV shows dedicated to the subject. Almost anyone can describe a relative or friend who has too many things and struggles to carry out everyday life activities. The problem is familiar to most of us and raises questions regarding how much is enough, where to keep things, and to whom to give things if we get rid of them. Although recent attention to hoarding sensationalizes the problem, hoarding behavior has been the subject of systematic empirical study in psychology, psychiatry, and related fields for nearly two decades. As early as 1947, Fromm (1) described a “hoarding orientation” in which a person’s security depended on collecting and saving objects. In 1963, Scandinavian psychiatrist Jens Jensen (2) referenced “collector’s mania” to describe senile elders who filled their rooms with too many objects.

In 1993, Frost and Shows (3) provided the first description of the behavioral manifestations of hoarding, saving, difficulty discarding, and acquiring. In 1996, Frost and Hartl (4, p. 341) defined hoarding as having the following three main characteristics: “1) acquisition of, and failure to discard a large number of possessions that appear to be useless or of limited value; 2) living spaces sufficiently cluttered so as to preclude activities for which those spaces were designed; and 3) significant distress or impairment in functioning caused by the hoarding.” This definition became the foundation for the development of the diagnostic criteria for hoarding disorder.

In 2013, the APA recognized hoarding as a unique disorder among obsessive-compulsive spectrum disorders (box). Six diagnostic criteria must be met for a patient to receive a diagnosis of hoarding disorder, which is currently classified under the code for obsessive-compulsive disorder (OCD; 300.3). Two specifiers provide descriptive ratings for acquiring and insight aspects of hoarding that may not be problematic for all patients.

Historically, hoarding has been considered a subtype of OCD, but recent evidence suggests that there are more differences than similarities. Studies of patients with OCD have shown an 18%–40% frequency of hoarding in adults as well as children and adolescents, although hoarding was identified as a major or primary symptom in <5% of cases (5). Differentiating hoarding disorder from hoarding symptoms caused by another mental illness can be challenging (6). In cases of OCD, excessive clutter might be better explained by an inability to discard or touch objects because of contamination fears or urges to check. Likewise, a patient experiencing a major depressive episode that provokes general behavioral deactivation may have difficulty discarding. If an individual does not display strong emotional ties to objects or does not experience significant distress about discarding, it is likely that hoarding disorder is not the appropriate diagnosis. The Structured Interview for Hoarding Disorder (SIHD) (7) is a useful diagnostic tool to help make this clinical differentiation (see the section on assessing hoarding symptoms below).

Hoarding is a surprisingly common condition, affecting 2%−5% of the adult population in industrialized countries (8–10). Epidemiological studies also suggest that hoarding occurs among both men and women, although women appear to volunteer for research studies more often than men. People who hoard tend to live alone, and many are not partnered (10, 11). In our clinical experience, people who hoard have sometimes reported a preference for being alone with their objects, indicating more reliable relationships with objects than with people. Many individuals who hoard do not recognize the extent of their clutter or the difficulty it provokes in daily life (12). This lack of insight can lead to increased health and safety risks, family frustration, and involuntary involvement with those mandated to uphold health and safety regulations (13). Poor insight may occur for a number of reasons. In some instances, a chaotic early life spent in an insecurely attached family in which excessive clutter was present can limit the opportunity to learn organization and decision-making skills (14, 15) and can reinforce poor housekeeping and a cluttered environment.

Treatment of people who hoard is made more complex by substantial clinical comorbidity. Major depressive disorder is the most common co-occurring mental illness, with a prevalence between 50% and 52% (16, 17). Other common comorbid conditions include social phobia (23%) and generalized anxiety disorder (24%) (16). Attention deficit symptoms are also present (25%−30%), with some variability by gender (16, 17). Impulse control disorders, especially excessive acquisition, have been noted in clinical hoarding samples, and approximately 10% of these individuals reported problems with kleptomania (16). Problems with indecisiveness, categorization, and related cognitive deficits are consistent with these conditions (18, 19). Hoarding also represents a significant public health burden in the areas of occupational impairment, poor overall physical health, and social service involvement (20). Hoarding was associated with an average of 7 work impairment days per month, increased likelihood of being overweight, and a variety of chronic medical concerns. People with hoarding disorder were five times as likely as those without hoarding to utilize mental health services, and 8%−12% had been evicted or threatened with eviction due to hoarding.

Serious hoarding also carries significant environmental risks for the person who hoards and for those living with or near the individual. Accumulated possessions can compromise the safety of a home or building because of blocked exists, high fire load, or excessive weight on floorboards. The inability to make repairs can result in serious plumbing, electrical, heating, and sewage problems. In high-density housing, fire risk is a serious concern, as evident in a 2010 Toronto high-rise fire that spread to accompanying floors and injured 17 people. A postfire inspection revealed that 2.7% of the units in that building were overstuffed with belongings, creating potentially hazardous conditions (21, 22). Significant clutter creates increased risks for insect and rodent infestation, mold growth, and unpleasant odors. As reported frequently in newspapers across the country, cluttered living spaces also create access and safety problems for first responders during home emergencies. Clutter avalanches can cause serious injury and even death. Not surprisingly, people who hoard can strain community agency fiscal and personnel resources. Even a few people with hoarding disorder can deplete the resources of community agencies and can cost communities large sums of money to clear clutter or demolish buildings that are no longer habitable. Frost et al. (23) reported that one health department spent $16,000 cleaning out a house and storing the occupant’s possessions to eliminate health and safety threats, only to repeat the process 1.5 years later when the same house was full again.

Assessing Hoarding Symptoms

Because hoarding disorder is a complex condition with multiple symptoms and associated features, clinicians and clients will benefit from a rapid but comprehensive assessment. Establishing the diagnosis of hoarding disorder facilitates a conversation about the meaning of this psychiatric condition and establishes access to third-party payments for services. Determining the severity of hoarding behaviors—acquiring, difficulty discarding, and clutter throughout the home and in other spaces—helps clarify where intervention efforts might begin and the potential barriers to making progress. Detailed assessment of the degree of impairment due to hoarding demonstrates the personal cost to the patient and indicates whether the clinician should be concerned about the patient’s health or safety; it also provides a ready avenue for motivational conversations about resolving frustrating functioning difficulties.

The SIHD (7) enables clinicians to assess DSM-5 diagnostic criteria as well as acquisition and insight specifiers. This tool also provides a means to rule out alternative diagnoses or medical conditions that better account for the patient’s symptoms. The SIHD is available as an appendix in the Oxford Handbook of Hoarding and Acquiring (24) and online (hoarding.iocdf.org/hoarding/assessment_tools.aspx#sihd).

A detailed hoarding interview (25, pp. 208–213) facilitates collection of detailed information about hoarding symptoms (including organization, acquisition, thinking, and emotions) as well as general life circumstances, living situation, social and family life, history of hoarding, and other problems. The interview also facilitates the development of a conceptual model for each patient’s hoarding symptoms and clarifies where to start the work (e.g., on acquiring habits or on dangerous clutter in particular areas).

The Hoarding Rating Scale (HRS) (26) is a convenient five-item scale to assess the main diagnostic features of hoarding, and the HRS can be completed by clinicians, patients, or family members. The HRS rates the severity of clutter, difficulty discarding, acquisition, distress, and interference on scales that range from 0 (no symptoms) to 8 (severe). The HRS has well-established reliability and validity, and a cutoff score ≥14 marks clinical levels of hoarding compared with normative samples. In a study by Tolin et al. (26), 24 was the average score of people diagnosed as having hoarding disorder.

The 23-item self-report Saving Inventory–Revised (SI-R) (27) contains subscales that assess acquiring (buying or accumulating free things), clutter, and difficulty discarding. A score ≥41 distinguishes clinical hoarding from normative behavior, and cutoff scores for each subscale are also available (25).

The pictorial Clutter Image Rating (28) allows clinicians to determine the extent of clutter by asking clients to point to the color photograph that most closely represents their living room, kitchen, and bedroom. Ratings for degree of clutter depicted in the photographs range from 1 (no clutter) to 9 (severe clutter), and scores ≥3 commonly indicate hoarding problems. The Clutter Image Rating provides an easy way to identify a suspected problem and quickly assess progress during treatment.

The Activities of Daily Living for Hoarding (29) is a 15-item self-report measure of how much hoarding interferes with everyday actions such as showering, dressing, and cooking, on a scale from 1 (none) to 5 (severe). Averaged scores ≥2.2 are typical of clinical levels of hoarding in the moderate and higher range.

Biological Models and Medication Treatments

Biological models for understanding hoarding symptoms derive from genetic and family studies, neurobiology, cognitive psychology, and animal models of hoarding behavior. Regarding heritability, family studies generally indicate that hoarding is more common among first-degree relatives of people with versus without hoarding disorder (unpublished paper by G. Steketee et al., 2015). Pedigree and twin studies indicate a strong genetic component to hoarding behavior, as well as a complex inheritance pattern. Genetic factors account for approximately 50% of the phenotypic variance in hoarding. Although several chromosomes (4, 5, 6, 14, 17, and 19) have been implicated, research is not definitive. Interestingly, a number of genes that have been linked to OCD do not appear to be relevant for hoarding (30). Unfortunately, very few of these studies have used samples with hoarding disorder diagnoses; they have relied mainly on OCD samples, which is a problem with much of the initial literature on hoarding. Replication studies to confirm these initial findings are certainly needed.

In a review of neuropsychological and neuroimaging studies of hoarding, Slyne and Tolin (31) suggested that both cognitive and affective brain circuits are involved in determining hoarding behavior. Research has connected hoarding to abnormal activity in the orbitofrontal cortex, dorsal anterior cingulate cortex (ACC), and superior temporal regions. Hoarding also seems to link to deficits during planning, contingency learning, and sustained-attention tasks, all of which are likely to impair decision-making functions. The brain regions that include the ventromedial prefrontal cortex and anterior insula suggest problems with emotional elements of decision making that might underlie the attachment to sometimes worthless objects described by people with hoarding disorder. The finding of neural hypoactivity in the insula and dorsal ACC outside of the decision-making process (32, 33) may account for the lack of self-awareness and self-regulation among patients with hoarding disorder, even when they are not actively sorting and discarding possessions. Slyne and Tolin (31) proposed a model of neurobiological abnormalities that may explain the fundamental impaired decision making that contributes to excessive acquiring, saving, and low insight. Specifically, they pointed to cognitive functioning problems (attention, memory strategy, or executive function) and faulty processing of reward and contingency information (impulsivity, failure to learn contingencies, or abnormal valuation). These deficits may lead to excessive emotional attachment to objects and strong negative emotions (sadness, grief, or anxiety) that impair decisions to discard items.

As Slyne and Tolin (31) noted, understanding the neurobiology of hoarding disorder will guide future treatment strategies because substantial room for improvement remains even for promising hoarding-specific psychotherapy and for serotonin reuptake inhibitor (SRI) medications for which efficacy results are mixed. They proposed that targeting cognitive and affective decision-making systems might directly reduce overactive frontal cortical regions and ACC by selected efforts to improve attention, memory strategies, executive functioning, and reward/contingency strategies and to decrease indecisiveness and cognitive failures. They suggest assessing improvement via cognitive processing detection tasks and behavioral assessments, rather than merely relying on self and assessor reports. Consistent with this approach, the use of cognitive remediation strategies (34) for older adults appears to target some of the neurocognitive functioning problems often found in hoarding. Preliminary data suggest that abnormalities in neural function may improve with cognitive-behavioral therapy (CBT) (35), and a recent pilot study of contingency management holds some promise (36).

Preston (37) summarized animal models for hoarding behavior, including larder and scatter hoarding and the biological substrates for these behaviors. As she noted, “hoarding” by animals is adaptive to ensure access to food when supplies are low and/or competition is present. Such hoarding behavior is critical to species survival. Interestingly, hoarding across human and rodent species shows some common behavioral features and brain structures. Hoarding is a common response to perceived shortages, uncertainty, and threat and is linked to physiological stress and the mesolimbocortical system (e.g., orbital frontal cortex, ventral striatum, and hypothalamus). A broader ecological view of hoarding across species and across disciplines is likely to engender research findings that facilitate understanding of hoarding behavior in humans as derived from basic structures and functions in mammalian species.

Although research on the biology and neurophysiology of hoarding suggests a variety of treatment avenues, the literature on medications has thus far focused primarily on SRIs because of their utility for OCD, with which hoarding disorder was initially thought to be associated. There is some disagreement about whether hoarding behavior improves with serotonergic drugs. Saxena (38) argued that SRIs appear to be as effective for hoarding symptoms as they are for nonhoarding OCD, whereas other reviews of this literature draw a different conclusion. A recent meta-analysis of 21 studies involving >300 patients with OCD with hoarding symptoms examined treatment response to pharmacotherapy, behavior therapy, and their combination (39). Seven studies showed that individuals with hoarding disorder consistently had a poorer response to medication treatments compared with those without hoarding disorder. Similar results were evident for combinations of medications and behavior therapy, although two studies were outliers in showing better response. The overall odds ratio for adult patients with OCD with hoarding symptoms was 0.42 for combination treatment and 0.49 for medication alone, which was well below the expected rate of 1.0 for any patient with OCD.

Remarkably, only two prospective psychopharmacology studies for hoarding have appeared thus far, both involving selective serotonin reuptake inhibitors. In an open trial of paroxetine, Saxena et al. (40) showed similar outcomes for both hoarding and nonhoarding patients, with 28% of the former and 32% of the latter considered full responders. Approximately 50% of each group showed full or partial response. In this study, hoarding/saving symptoms improved as much (mean 24%) as other OCD symptoms. A more recent 12-week open trial of extended-release venlafaxine with 24 hoarding patients (41) indicated that hoarding symptoms decreased by 32% on the SI-R and 16 of 23 (70%) completers were considered responders, which was a strong response rate. These studies suggest that serotonergic medications may be useful for hoarding disorder; however, controlled trials are lacking at this time. Almost no data on non-SRI medications for hoarding are available, although case reports have described hoarding that responded to glutamate modulators (42, 43). Future research might test medications that could influence information-processing deficits (e.g., attention, decision making, organization, or categorization), perhaps including stimulants to increase ACC activity (31).

Another question has to do with the potential value of adding medications to cognitive-behavioral treatments for hoarding. In their meta-analysis, Tolin et al. (44) reported a significant positive predictive effect of medication for improvement in difficulty discarding, but not for overall hoarding severity or other symptoms of hoarding. However, the type of medications varied within and across studies; thus, the possible augmenting effects of specific medications are not yet clear. Additional research is needed to determine the efficacy of medications for hoarding disorder, alone and in combination.

Cognitive-Behavioral Model for Hoarding Disorder

In addition to the above-described biological models and treatments, a cognitive-behavioral model of hoarding originally described by Frost and Hartl (4) has accumulated noteworthy research support. An updated version of this model (45) posits underlying vulnerability factors for hoarding that include the biological features discussed earlier, as well as family and social experiences that promote dysfunctional emotional attachments to, and erroneous beliefs about, possessions. These include negative early developmental influences, such as loss and disruption (46), and information-processing difficulties, such as attention, memory, and executive functioning problems manifest in impaired decision making, categorization, and impulsivity [for review, see Timpano et al. (47)].

These personal, family history, and cognitive vulnerabilities are hypothesized to promote general negative mood (both depression and anxiety), as well as strongly held beliefs and attachment to objects that are accompanied by both positive and negative emotional reactions. That is, acquiring and saving is reinforced both by the strong positive emotions (e.g., pleasure, joy, or excitement) that follow these behaviors and by the avoidance of negative emotions (e.g., anxiety, guilt, regret, or sadness). For example, a woman who fears that she will soon need an item or might be wasting a useful object will avoid these states by keeping the object she is considering discarding. Similarly, she might purchase an item to prevent future regret at not having acquired it. This combination of both positive and negative reinforcement mechanisms creates a compelling motivation to engage in dysfunctional hoarding behaviors, even at the cost of losing one’s financial stability and one’s home. This parallels models for addictions and, to a lesser extent, obsessive-compulsive spectrum conditions such as trichotillomania and impulse control disorders such as kleptomania. The heuristic value of this explanatory model is evident in the efficacy of the CBT methods that it has spawned, which are described briefly below.

Insight and Motivation

Early treatment research on hoarding suggests that motivation to correct the problem is often lacking, even for some patients who actively seek therapeutic help (48). Of course, patients with poor or absent insight would typically not seek help for their behavior and might actively resist uninvited intervention efforts. The research literature on insight and motivation in hoarding disorder is limited. As Worden et al. (36) noted, insight in hoarding disorder is multidimensional, encompassing anosognosia (awareness of illness), overvalued ideas, and defensiveness that may stem from family or community efforts to force a reduction of clutter to meet housing or other code requirements. To date, there are no standard measures of motivation for treatment or for insight in people with hoarding disorder. Yale-Brown Obsessive Compulsive Scale question 11 has been utilized for this purpose in studies of hoarding in the context of OCD, but it is not clear that this single item accurately reflects hoarding patients’ views of the reasonableness of their acquiring, saving, and clutter. Worden et al. (36) proposed the use of cognitive insight measures for hoarding disorder because these have been helpful in assessing awareness of illness in schizophrenia and other conditions.

Some studies recruiting patients with hoarding disorder have utilized observer ratings and discrepancy scores to gauge insight. In a web-based survey, family/friend informants’ average ratings of loved ones with hoarding disorder indicated fair to poor insight, with over one-half described as having poor to delusional insight (12). These family members/friends gave significantly higher severity ratings to the hoarding behavior compared with their estimates of how the person with hoarding disorder would rate his or her own symptoms. DiMauro et al. (49) assessed insight by contrasting the severity ratings of clutter from participants with hoarding disorder with ratings of family members and evaluators. They observed that patients reported less severity than did friends or family, but family members’ rejecting attitudes toward the participant at least partly accounted for their higher ratings. Interestingly, in a second study, participants with hoarding disorder appeared to underreport their hoarding symptoms while overreporting overall hoarding severity. This is a confusing finding that suggests varying views held by patients with hoarding disorder compared with those of family members and others. From a clinical standpoint, patients with hoarding disorder appear to waver in their perspective depending on their emotional state (both positive and negative) at the time of the conversation.

CBT Treatment

CBTs found effective for OCD have produced generally poorer outcomes for adults who hoard. A recent meta-analysis by Bloch et al. (39) reported an odds ratio of 0.60 for eight studies that compared outcomes for patients with OCD with and without hoarding. Those with hoarding symptoms had a significantly worse response to CBT. As such findings have accumulated in the literature, it is not surprising that clinical researchers have developed a multicomponent psychotherapy designed to address hoarding symptoms based on the above-described cognitive-behavioral model for hoarding disorder. This treatment includes education about hoarding disorder, goal setting and motivational enhancement, organizing and decision-making skills training, cognitive therapy aimed at problematic beliefs about acquiring and saving possessions, and practice resisting acquiring, sorting, and discarding objects. Regular home visits were strongly recommended and have been applied in most outcome studies. An initial pilot study of 14 patients showed that 26 sessions of treatment over 7–12 months produced improvement for five of 10 completers (50). A subsequent waitlist-controlled study of 40 patients with hoarding disorder indicated that the combined CBT intervention led to significantly better outcomes than a waitlist condition after 12 weeks (51). After 26 sessions of CBT for 36 completers, therapist ratings showed that 71% of participants were “much” or “very much” improved; these corresponded to participant self-ratings of 81%. Clinically significant improvement was evident for 41% of patients with hoarding disorder. Twelve months after treatment, similar gains were found for 62% of patients with hoarding disorder according to therapist ratings and 79% according to patient ratings (52). More severe initial hoarding symptoms, male gender, and more perfectionism and social anxiety predicted worse outcomes after treatment (N=37). Only more perfectionism and male gender predicted worse outcomes at follow-up (N=31). Patients who refuse treatment or fail to comply with instructions remain a concern for this CBT method.

Subsequent studies have tested a variety of delivery formats for these combined CBT methods, including manualized individual treatment for older adults, therapist-guided groups, peer-led bibliotherapy groups, and web-based groups. Tolin et al. (44) conducted a meta-analysis of 10 CBT outcome studies with 12 distinct samples, for a total of 232 patients treated for hoarding disorder. Treatment length ranged from 13 sessions for peer-led groups to 26–35 sessions for individual treatment. All individual therapy studies included periodic in-home sessions, as did three of the five therapist-led group treatments. All interventions led to significant improvement at posttreatment compared with baseline, with an average Hedges’ g effect size of 0.82 for total hoarding disorder severity. The largest effect (0.89) was observed for difficulty discarding, which was a target symptom for all CBT interventions, with a somewhat smaller overall effect (0.70) for clutter and for impairment (0.52). These more modest effects are not surprising because clutter is a byproduct of difficulty discarding and excessive acquiring and often takes more time to resolve, especially in severe cases. Male gender, older age, fewer CBT sessions, and fewer home visits predicted worse clinical outcomes across these trials. Most samples showed reliable change on outcome measures, with somewhat lower rates of clinically significant change, ranging from 24% to 43%. In practice, this means that most patients’ posttreatment scores did not move them into the nonclinical range for hoarding disorder symptoms. It is clear from these studies that this form of psychotherapy for hoarding disorder is effective, but there is still much room for improvement. In addition, most of these studies have been conducted with mainly white female samples; thus, testing of CBT with more diverse samples is clearly needed.

Special Populations

Children

Although hoarding behavior typically begins in childhood and adolescence (11), study of the phenomenon in children is limited. Because there are no prospective studies on hoarding in children thus far, our understanding is drawn mainly from hoarding among children presenting to OCD clinics. Children who hoard tend to collect seemingly useless items (e.g., candy wrappers or old school papers). This collecting is similar to normative collecting but is accompanied by excessive concern about the whereabouts, care, and condition of the objects, sometimes to the extent of fixation. Children rarely accumulate clutter as adults do because their parents, teachers, and others control the acquisition, saving, and cluttering behaviors (53). Children personalize objects, worry about harming them, and consider objects part of their personal identity (54). Discarding may be so distressing that children experience it as a traumatic event. To cope with these feelings, children who hoard may try to prevent their parents from entering their room. Key markers of hoarding in children include distress, associated avoidance, information-processing problems, and emotional attachment to and anthropomorphizing of objects (53). Information-processing deficits mirror symptoms found in adults and include difficulty with memory, planning, attention, problem solving, and task completion (55).

Unfortunately, most standardized measures for adults have not been normed for use with children, with the exception of the Children’s Saving Inventory (CSI) (55). The CSI is based on the (SI-R) (see above), and it is the only psychometrically validated measure of hoarding for children. The CSI is a 23-item scale rated by parents or caregivers on four subscales: discarding, clutter, acquisition, and distress/impairment. The only tested treatment for children who hoard is CBT involving the caregiver (53). Modules include exposure and prevention of hoarding behaviors, contingency management, and basic cognitive strategies. This treatment may be complemented with medication management, although the efficacy of pharmacotherapy for hoarding in children consists of only a few case studies.

Older Adults

Functional impairment combined with age-related cognitive decline makes addressing hoarding in older adults especially challenging. Most older adults report that their hoarding began early in life. Some have reported late onset, but this may not be accurate, according to research by Ayers et al. (56), which indicated that the course of hoarding was chronic and worsening. There was no evidence of symptom remission or decreased severity over the life course. Adverse consequences include lack of regular medical care, difficulty managing medications, problems with diet and nutrition (57), and worsening medical conditions such as emphysema (58). Falls, ambulation problems, and nonfunctioning appliances are additional concerns (59). Older adults who live alone and are socially isolated may hide even severe hoarding until a significant event such as a medical emergency occurs and first responders arrive to find unlivable home conditions. Such seniors suffer shame and embarrassment and often face housing relocation (57).

Instruments described earlier for adults are generally suitable for assessing hoarding in older adults, unless marked cognitive decline invalidates self-report measures. A comprehensive assessment should include a clinical interview, home visits, family/friend reports, neurocognitive assessment, and evaluation of functional impairment and comorbid psychiatric conditions (60). Intervention typically focuses on clearing clutter and reducing the potential for harm (61), even when cognitive impairment and treatment refusal are present. The older adult is included as a harm reduction team member alongside family, friends, clinicians, and other human service professionals who seek to reduce the risks in the home. For older adults who are willing and able to participate in standard CBT for hoarding, some age-related accommodations include spending extra time on education about hoarding and building motivation (34), as well as cognitive rehabilitation and focus on exposure with limited use of cognitive strategies such as Socratic questioning (62). Exposure activities will need to be modified to fit the patient’s mobility and energy level.

Nonvoluntary Clients

Contextual factors and low insight can set hoarding apart from other psychiatric conditions and can make assessment and intervention more complicated. For example, a hoarding client may simultaneously face eviction from his or her home, investigation by protective services, and the ruin of a marriage. When individuals lacks awareness that their current struggles are provoked by their acquiring-and-saving behavior, the problem often becomes quite severe and presents significant health and safety threats to vulnerable people in the home (e.g., children, people with disabilities, or older adults) before intervention begins.

The study of hoarding among nonvoluntary clients in community settings is limited. A wide range of human service professionals may become involved, especially when there are significant threats to health and safety. First responders, protective service agencies, and housing/building inspectors often are the first to identify and try to address the problem according to the nature of their work (13). Public health agencies, the legal system, mental health clinicians, vector control, nursing staff, and professional organizers can become part of the intricate web of professionals involved in intervention. Unfortunately, some clients who become public cases are unable to recognize their behavior as problematic and remain unmotivated to work with professionals to make changes. Shame and embarrassment are also factors that lead to refusal of assistance (13). Models of community-level hoarding intervention are emerging that utilize informal partnerships or networks, as well as public and private partnerships and community task forces. The goals of community-based coordinated initiatives typically include preserving tenancy, decreasing the incidence of severe hoarding, and increasing the physical and mental health of individuals who hoard (13). Although research on outcomes of community-based hoarding is only beginning, a recent report suggests that housing inspection services that are focused on reducing risks can lead to tenancy preservation for >90% of clients served (63).

Family Members

Family members who live with a person who hoards are exposed to the same health and safety risks as the person who hoards. Adult children of people who hoard report significant childhood distress and burden due to the emotional and physical hardships of living in a hoarding situation (20). Even family members who do not live in the same household report excessive worry about their loved one and may engage in pleading and ultimatums as well as efforts to clear the home without permission. Lack of action by the person who hoards can provoke hostility and rejection by family members and can lead to family disengagement over the hoarding problem (64).

Family-focused harm reduction intervention (65) aims to improve stressed familial relationships while encouraging the person who hoards to accept help to manage the hoarding problem. The harm reduction approach includes five key components: enhance willingness to engage in the harm reduction approach, assess the potential for harm, build and facilitate a harm reduction team, plan the harm reduction approach, and implement and manage the plan. In some instances, the direct involvement of family members may not be possible or productive because of the nature of the family relationships. In these cases, populating the harm reduction team with applicable human service professionals is appropriate (unpublished 2014 paper of B. L. Worden). To date, no research on the outcomes of this effort are available.

Conclusions

A tremendous amount of research has followed in the nearly two decades since the 1996 Frost and Hartl (4) seminal article on hoarding. This research has clarified the specific symptoms of hoarding (what it is and what it is not from a diagnostic perspective), culminating in the inclusion of hoarding disorder in the DSM-5. The features of hoarding disorder are fairly clear, with the exception of whether it is truly more common among women (who are heavily represented in psychopathology and treatment studies) or whether men also have the disorder at high rates but fail to volunteer for research. We also lack information on cultural and racial/ethnic differences within and across the United States and other countries. Clarity on these points can be obtained through conducting additional epidemiological studies using adequate assessment methods and by recruiting participants in community-based settings outside of clinical mental health treatment contexts.

The model for understanding hoarding disorder focuses on vulnerability factors such as family experience, as well as cognitive, biological, and emotional features, many of which have been established through research studies. Of particular interest are recent studies investigating cognitive processing and brain morphology aspects of hoarding. These investigations hold promise for clarifying underlying substrates for difficulty with discarding, excessive acquiring, and clutter. Likewise, the parallels in brain structures and functioning between human and animal hoarding are intriguing. Much work remains to be done in these areas, which have considerable potential to contribute more advanced treatment strategies to resolve hoarding disorder.

Among existing empirically tested treatments for hoarding disorder, cognitive and behavioral methods that are adapted to the developmental stage of the participant (child, adult, or elderly individual) show the most benefit at this stage of research. These treatments can be delivered effectively in individual and group modalities. Medication trials are few, and although two SRIs have been tested, it is not clear that these will outperform CBT methods, and augmentation strategies have not been examined. It seems likely that a stepped-care treatment model will be useful, with motivated moderately affected adults receiving the least costly treatments, whereas more intervention involving more care providers will be needed for those with less insight and more severe symptoms. Community and family care models are of great interest, given the need for harm reduction strategies, but this research is more difficult to accomplish and will require different research designs and methods. Overall, great strides have been made in understanding and treating hoarding disorder over the past two decades, and it is likely that we will learn a great deal more about this order within the next 10 years.