Overview

Hoarding disorder (HD) is defined as the acquisition of—and inability to discard—a large number of possessions, to a degree that precludes intended use of living spaces and creates significant distress or impairment in functioning. Hoarding can interfere with an individual’s ability to work, interact with others, and perform basic activities, such as eating or sleeping. In severe cases, it may lead to dangerous, even life-threatening living conditions. Hoarding also is associated with a profound public health burden. In a survey of local health departments, 64% of health officers reported receiving hoarding complaints, some of which resulted in a significant cost to the community. A large Internet survey of self-identified hoarding participants (N = 864) and family members (N = 655) revealed that compulsive hoarding is related to poor physical health, social service involvement, and significant occupational impairment.

Hoarding has been linked previously to anxiety disorders, specifically obsessive-compulsive disorder (OCD); however, it is now defined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) as a discrete disorder. Consistent with prominent models of anxiety disorders, individuals who hoard frequently report feelings of anxiety when they are asked to discard or organize their possessions. They also may demonstrate avoidance and safety behaviors connected to their hoarding-related beliefs and fears. There is, however, a pleasurable or gratifying component associated with acquiring, collecting, and saving possessions that distinguishes hoarding from other anxiety-related problems.

This appetitive aspect of hoarding suggests that there are similarities between hoarding and behavioral addictions, which include several impulse control disorders (pathological gambling, pyromania, and kleptomania). In behavioral addictions, individuals experience pleasurable or gratifying feelings while engaging in the target behavior, followed by a decrease in arousal and feelings of guilt and remorse. An individual who compulsively collects items from yard sales and thrift stores may similarly feel a rush of positive emotion upon finding an item that she feels is unique or valuable, followed by feelings of regret when she reflects upon how much the clutter is overtaking her home and negatively impacting her life. Although the anxiety-related aspects of hoarding have been the subject of several investigations, the appetitive nature of this syndrome has been relatively understudied. Hoarding behavior is sometimes motivated by a desire to reduce anxiety; however, there are cases in which hoarding appears to be driven by anticipation of pleasure and impaired self-regulation. There also may be cases in which both avoidance and approach behaviors play a role. From a clinical perspective, this underscores the importance of functional analysis in determining motivation for hoarding and, more specifically, acquisition behaviors.

Classification and Comorbidity

Hoarding was long considered a dimension or subtype of OCD. Findings of moderate frequencies of hoarding behavior in OCD populations, ranging from 18% to 33%, supported this association. Moreover, several studies found that individuals who hoard report more OCD symptoms than nonhoarding individuals do. Frost and colleagues compared individuals with OCD who hoarded versus those who did not, and found that the two groups did not differ on the number of OCD symptoms displayed, although they both reported more OCD symptoms than did anxious and nonclinical control participants.

Despite this association, mounting evidence began to suggest that hoarding was distinct from other OCD symptom dimensions. Most factor analyses of OCD symptoms found that hoarding constituted a separate factor from other obsessions and compulsions. Furthermore, hoarding behavior has been reported in a variety of psychiatric disorders besides OCD, including schizophrenia, organic mental disorders, eating disorders, brain injury, and dementia. Finally, hoarding is typically a poor predictor of treatment outcome in both psychological and pharmacological treatments for OCD, although several recent studies have not confirmed this association. In light of the conflicting evidence regarding the diagnostic status of hoarding, Wu and Watson examined the relationship between OCD and hoarding in two large samples. They found that hoarding correlated only modestly with other OCD symptoms, which reliably correlated with each other. Furthermore, hoarding was not more strongly associated with OCD symptoms than other dimensions of psychopathology, such as depression. Subsequently, large epidemiological studies have demonstrated that hoarding difficulties are more prevalent than first thought, and are not definitively associated with one particular disorder. Together, this research led to the development of criteria for hoarding disorder, which were included in the DSM-5.

It is notable for the present discussion that not all individuals who hoard have comorbid symptoms reflective of typical OCD. In addition, hoarding beliefs and behaviors do not always fit the OCD model. Steketee and Frost noted that hoarding thoughts may not always impel the associated compulsive behaviors, may not be as intrusive as typical obsessions, and are not always viewed as ego-dystonic by the individual. In addition, many individuals who hoard lack insight into the severity of the consequences of their behaviors and can experience attenuated levels of distress compared with OCD clients. The lack of insight and ego-syntonic nature of hoarding is similar to that observed in some addictive and impulse control disorders, suggesting some overlap in phenomenology between hoarding and many behavioral addictions.

Hoarding and Impulse Control Disorders

Most relevant to the current chapter is the association between hoarding and the spectrum of impulse control disorders. Impulse control disorders are positively reinforcing to the individual and are associated with a wide variety of emotional states, including pleasure or gratification. They are characterized by repetitive behaviors and impaired inhibition of these behaviors, and include pathological gambling, skin picking, and trichotillomania. Researchers have suggested that impulse control disorders may best be conceptualized as part of an obsessive compulsive spectrum, as the urges and subsequent behavioral responses observed in impulse control disorders appear, at least superficially, similar to the excessive rituals observed in OCD. Problems removing unwanted thoughts and deficits in decision making may also represent commonalities between OCD and impulse control disorders.

A key difference between impulse control disorders and OCD, however, is that an individual with an impulse control disorder experiences feelings of pleasure and gratification while engaging in the target behavior, in contrast to the anxiety experienced when individuals with OCD engage in a compulsion. For example, the repetitive and often harmful rituals performed in OCD may appear similar to the wagering behaviors of compulsive gamblers. When significant monetary losses fuel chasing behavior, a compulsive gambler may feel compelled to gamble to avoid negative consequences in much the same way that rituals in OCD are performed in an effort to alleviate negative emotional states such as anxiety, shame, and guilt. However, gambling behaviors are clearly pleasurable and reinforcing. Individuals who hoard also derive a sense of pleasure and gratification from their acquisition behaviors, which may suggest that hoarding fits better among the impulse control disorders than its common conceptualization as a subtype of OCD.

Hoarding has been linked to poor impulse control in a variety of studies, suggesting the possibility of a common diathesis underlying both hoarding and certain impulse control disorders. Samuels et al. ⁸³ reported a greater frequency of trichotillomania and skin picking among hoarding compared with nonhoarding individuals with OCD. Rasmussen et al. found that hoarding individuals displayed poor response inhibition on standardized laboratory tasks relative to individuals with anxiety disorders, despite reporting similar levels of impulse control.

Frost et al. found that pathological gamblers reported significantly more hoarding symptoms than light gamblers and speculated that both hoarding individuals and gamblers may share similar concerns about the loss of potential opportunities. Hoarding individuals believe that items may be needed for some future use and, therefore, fear discarding items as this would represent a lost opportunity for the item’s use, with some research suggesting that even the sight of a possession can trigger this fear. Frost and colleagues have suggested that pathological gamblers may have difficulty refraining from purchasing chances because of similar beliefs and fears about losing an opportunity to gain financial benefit. Although Grant et al. found a low prevalence of impulse control disorders overall among individuals with OCD, OCD participants with a lifetime and current impulse control disorder were more likely to report hoarding symptoms. In addition, some research suggests that beliefs about possession and about buying are similar to the beliefs of those with compulsive hoarding. The association between hoarding and impulse control disorders is consistent with McElroy and colleagues’ conceptualization of a compulsive-impulsive spectrum but requires further exploration.

Hoarding and Compulsive Acquisition

Compulsive acquisition is a central component of hoarding, and is of particular significance when considering hoarding as a behavioral addiction. The compulsive acquisition component of hoarding consists, in part, of compulsive buying, which is classified as an impulse control disorder. Compulsive buying has been defined as chronic, repetitive purchasing behavior in response to negative events and or/feelings that is difficult to stop and results in harmful consequences. Similar to other impulse control disorders, compulsive buying is associated with a pattern of tension, pleasure, and subsequent feelings of guilt and remorse. A high level of compulsive buying has been found among individuals who hoard, and, conversely, a high level of hoarding symptoms have been found in compulsive buyers. A study comparing compulsive buyers with noncompulsive buyers found that compulsive buyers scored higher on both OCD and hoarding symptoms, but the relationship between buying and OCD was mainly mediated by hoarding. Of interest, this study found that while not all compulsive buyers suffer from compulsive hoarding, nearly all hoarding participants suffer from compulsive acquisition. Compulsive acquisition in hoarding, however, is not limited to buying, but includes collecting free things that are being given away or that have been discarded by others. However, Frost et al. found that these behaviors were related; a measure of compulsive buying behavior was associated with a compulsive acquisition of free items.

The relationship between hoarding and compulsive buying may be accounted for by shared cognitive deficits and emotional dysregulation. Both hoarding and compulsive buying appear to be closely related to impaired mental control and fears about decision making. In addition, evidence suggests that similar cognitive biases about the meaning of possessions exist in both hoarding individuals and compulsive buyers. Although O’Guinn and Faber suggested that compulsive buyers may derive more emotional pleasure from the process of acquiring items, in contrast to hoarding individuals, who retain a sense of satisfaction from items even once ownership has been established, Kyrios et al. found that compulsive buyers did hold beliefs about possession similar to those reported by hoarding participants. These beliefs included fears over lost opportunities to obtain objects, erroneous beliefs about the inherent value of possessions, and beliefs about personal responsibility for objects. Research on hoarding has suggested that the sight of a possession activates the fear of losing an opportunity.

Compulsive buying and hoarding also share problems with regulating emotions. Individuals who buy compulsively report difficulties accepting and coping with negative emotions, similar to the difficulties in managing emotional distress that hoarding individuals report, both in response to their objects and in day-to-day life. Compulsive buying and hoarding both appear to be driven by negative urgency—a tendency to react impulsively when experiencing negative emotion—which, in hoarding, intensifies emotional attachment to possessions. Compulsive buying and hoarding difficulties are also related to low distress tolerance, in particular a low perceived ability to cope with distress, and the tendency to become absorbed or overwhelmed by the experience of distress. Collectively, these findings suggest a diagnostic overlap between hoarding disorder and impulse control disorders.

Etiology/Biobehavioral Underpinnings of Hoarding

Over the past decade, much new evidence has emerged regarding the biological/neural underpinnings of hoarding. Several case reports have described cases of pathological collecting and saving that began after a brain injury, typically along with other changes in personality and social functioning. These cases suggest that hoarding may be related to frontal lobe dysfunction. Other evidence for the biological correlates of hoarding has come from three domains of research: neuroimaging, electrophysiology, and genetics.

Cognitive-Behavioral Theory and Evidence

Current cognitive-behavioral conceptualizations specify a multidimensional model to explain the core manifestations of compulsive hoarding. Hoarding is posited to develop as a result of conditioned emotional responses associated with certain thoughts and beliefs concerning items or possessions. Acquisition and failure to discard possessions represent avoidance of the anxiety associated with discarding and decision making. In addition, similar to other behavioral addictions, excessive saving behavior is positively reinforced because the possessions attain a pleasurable or comforting quality. The prominent model of compulsive hoarding proposed by Steketee and Frost consists of four main components: information-processing deficits, beliefs about and emotional attachments to possessions, and emotional distress and avoidance behaviors that develop as a result.

Information-Processing Deficits

The cognitive-behavioral model of hoarding suggests that individuals who hoard may possess information-processing deficits that result in confusion or misinterpretation about the value of possessions and difficulty organizing and discarding. Several neuropsychological studies of compulsive hoarding support the notion that there are cognitive deficits associated with this syndrome.

Grisham et al. compared a compulsive hoarding group with a mixed clinical group and a community control group on a number of measures for attention, working memory, and verbal and nonverbal intelligence. They found that those in the hoarding group had intact verbal intelligence and working memory but were impaired on measures of attention and nonverbal intelligence. They also were slow to initiate responses and had difficulty inhibiting impulsive responses. Similarly, Hartl and colleagues found that hoarding adults displayed symptoms consistent with attention-deficit/hyperactivity disorder on a self-report measure. Weaknesses in these neuropsychological domains of attention and nonverbal intelligence may, therefore, limit a hoarding individual’s ability to sustain attention during a task (e.g., when deciding what possessions to save or discard) and to organize their possessions and reduce clutter. Other studies have found evidence for indecisiveness and deficits in verbal and nonverbal memory. Mackin et al. compared 78 HD individuals to a healthy comparison group across multiple neuropsychological tests examining memory, reasoning, decision-making and speed-of-processing. Relative to healthy participants, HD individuals displayed impairment in detecting, remembering, and categorizing visual information. However, when test-by-test comparisons were made within groups, HD displayed relative cognitive strengths in abstract reasoning using both verbal and visual information.

Hoarding behavior also appears to be associated with specific deficits in organizing and categorizing common objects. Wincze et al. compared the performance of hoarders with the performances of nonhoarders who had OCD and control participants on a sorting task. They found that participants in the hoarding group were underinclusive (i.e., they sorted the objects into a larger number of categories) compared with control participants. They also took a longer time than the controls to decide in what category the objects belonged, and they reported more distress during the sorting task. This was only true, however, when they were sorting personally relevant objects. These results suggest that the information-processing deficits due to an underinclusive categorization style are not global but are specific to relevant objects. Wincze at al. suggested that a hoarding individual’s difficulty categorizing objects may be due to the meaning attached to objects, which influences what features of the object are attended to during a sorting task. Luchian et al. replicated this study with nonclinical hoarding and control participants and found similar results.

There are some inconsistencies in the research on hoarding and associated neuropsychological deficits. Although Grisham et al. found that hoarding individuals displayed relatively intact decision making on a gambling task, Lawrence and colleagues found that hoarding symptoms were associated with specific decision-making impairments on the same gambling task, in addition to poor set shifting on a sorting task. Lawrence et al. suggested that hoarding individuals have difficulty deciding whether to save or discard a possession due to these difficulties in decision making. In addition, the risky behaviors exhibited by hoarding participants suggest that problems with impulse control may contribute to difficulties in decision making. Grisham et al. did observe greater impulsivity in the hoarding group on measures of attention. The discrepancies between these studies are likely due to differences in the samples selected. In the Grisham et al. study, the hoarding group consisted of participants who met the then proposed criteria for HD, regardless of whether they had OCD, while the hoarding group in Lawrence et al. comprised individuals with OCD who also displayed hoarding behaviors.

The recent findings on specific neuropsychological characteristics associated with hoarding may elucidate the relationship between hoarding and addictions. Addictive disorders are characterized by repeated behaviors that are pleasurable to perform. Hoarding may similarly be associated with a pleasurable state upon acquisition of new items, but hoarding behaviors are also viewed as an attempt to avoid the emotional distress associated with discarding. Although the motivations behind the behaviors (pleasure seeking versus distress avoiding) may vary, there is a degree of overlap that may be accounted for by similar neuropsychological deficits. Lubman et al. argued that problematic drug use is associated with decreased inhibitory control, thus compromising decision-making ability. The poor inhibition and decision making are also evident in compulsive hoarding. The deficits observed in hoarding participants on the gambling task have also been found with drug-addicted individuals. Furthermore, these individuals show behavioral responses similar to the hoarding participants observed by Lawrence et al. and individuals with lesions to the orbitofrontal cortex, the same region implicated in positron emission tomographic studies of hoarding individuals. Drug-addicted individuals also show deficits in response inhibition similar to those observed by Grisham et al. with hoarding participants.

Emotional Attachment to Possessions

Maladaptive beliefs and excessive emotional attachment to possessions are also posited to play a central role in the maintenance of compulsive hoarding. Research suggests that object-related beliefs cluster into four basic types: emotional attachment to possessions, memory-related concerns, responsibility for possessions, and control over possessions. The beliefs and cognitions associated with excessive saving range from exaggerations of common beliefs, for example, “I need these sentimental possessions to remind me of important events in my life” to more idiosyncratic reasons for saving, for example, “These used Band-Aids are a part of me because they contain my blood.” The individual’s unrealistic beliefs about possessions are associated with excessive emotional attachment to objects, which leads to delaying or avoiding the process of making decisions and discarding. Being particularly sensitive to anxiety or prone to rash decision-making appears to intensify beliefs about emotional attachment to possessions, which, in turn, exacerbates hoarding behavior.

Excessive attachment to possessions can lead to a sense of grief and loss when individuals with compulsive hoarding are forced to discard items. These reactions can even be comparable to the grief experienced due to the death of a loved one, a finding that accords with a tendency for hoarding individuals to imbue their possessions with human qualities, thereby anthropomorphizing them. As these reactions can inevitably provoke anxiety, avoidance of discarding is negatively reinforced because it prevents the experience of these emotions. Anxiety can also arise when others attempt to arrange or utilize a hoarding individual’s possessions. Control over possessions appears to be partly related to a heightened sense of responsibility for keeping objects intact and to a sense of personal responsibility for being prepared in the event that an object is required at some point in the future.

Assessment of Compulsive Hoarding

In early hoarding research, many studies used measures of OCD that included hoarding subscales, such as the Yale-Brown Obsessive Compulsive Scale, the Obsessive Compulsive Inventory, and the Obsessive Compulsive Inventory-Revised. Some researchers raised concerns about using these items due to questions about the definition of a hoarding obsession and the inability of these two items to assess many crucial aspects of hoarding behavior. One study of hoarding used the Dimensional version of the Yale-Brown Obsessive Compulsive Scale. This version was designed to assess OCD dimensions (contamination, cleaning, harm, hoarding, symmetry, sexual/religious, and miscellaneous obsessions and compulsions). The Dimensional version of the Yale-Brown Obsessive Compulsive Scale includes a series of clinician-administered scales that can be used to assess the presence and severity of each symptom dimension.

The Obsessive Compulsive Inventory and Obsessive Compulsive Inventory-Revised comprise several symptom subscales including Washing, Checking/Doubting, Obsessing, Mental Neutralizing, Ordering, and Hoarding. Both measures are somewhat better than the Yale-Brown Obsessive Compulsive Scale at assessing hoarding; however, the Hoarding subscales of both the original and revised Obsessive Compulsive Inventory can be problematic. This subscale failed to distinguish clinical from nonanxious controls adequately in the original Obsessive Compulsive Inventory, and the revised inventory has demonstrated weak internal consistency. In addition, Abramowitz and Deacon found that the Obsessive Compulsive Inventory-Revised hoarding subscale correlated only weakly with the other Obsessive Compulsive Inventory-Revised subscales and did not correlate with the Yale-Brown Obsessive Compulsive Scale in a clinical sample of anxious participants. A recent adaption of the Obsessive Compulsive Inventory-Revised added three hoarding questions that better reflect the current DSM-5 criteria for HD, resulting in the OCI-HD. The OCI-HD demonstrated significantly greater diagnostic specificity than the original measure, correctly classifying 93% of clinically significant hoarding cases. Although some concerns remain about the appropriateness of utilizing OCD measures to index hoarding thoughts and behaviors, the new OCI-HD instrument seems to provide a robust identifier of clinically significant hoarding in OCD samples.

Due to growing interest and research in hoarding, several measures have been developed to assess hoarding symptom severity and establish an HD diagnosis. The first systematic attempt to design a scale solely to measure hoarding symptoms was the Hoarding Scale, a 22-item self-report questionnaire that assessed discarding behaviors, emotional reactions to discarding, problems with decisions regarding discarding, concerns over future use of discarded items, and sentimental attachment to possessions. The Hoarding Scale was found to be both reliable and valid in college, clinical, and community samples. In addition, it could discriminate between individuals who reported experiencing hoarding tendencies and community controls. Although it possessed sound psychometric properties, the Hoarding Scale had inherent limitations, as subsequently identified by the primary author. Given the limited information about hoarding behaviors at the time of its development, the Hoarding Scale did not assess all of the components that are now known to be important facets of hoarding, such as excessive acquisition. The scale also confounded beliefs about possessions with behavioral symptoms and included items about specific types of possessions that were not applicable to every individual with hoarding tendencies. In addition, the Hoarding Scale did not adequately assess distress or impairment at the clinical/severe level.

The recognition of the Hoarding Scale’s limitations led to the development of a revised measure to address these concerns, the Saving Inventory-Revised —a 23-item self-report questionnaire with three subscales assessing: (1) excessive acquisition of purchased and free items, (2) saving and discarding behaviors, and (3) excessive clutter as a result of these behaviors. The Saving Inventory-Revised has been shown to discriminate between identified hoarders and both nonhoarding controls and nonhoarding OCD cases. The subscales have been shown to correlate with additional indices of hoarding interference, such as activity dysfunction and both self- and observer ratings of clutter in the home.

There are several other self-report measures of hoarding. One commonly used measure, the Saving Cognitions Inventory, is a 24-item self-report inventory that assesses beliefs and attitudes experienced when a person is trying to discard possessions. On a 7-point Likert scale, participants rate the extent to which a thought influences their decision about whether to discard a possession. The four subscales assess emotional attachment to objects, beliefs about objects as memory aids, responsibility for not wasting possessions, and the need for control over possessions, respectively. In addition, a few studies have employed the Yale-Brown Obsessive Compulsive Scale: Acquisition and Saving Version, a 10-item self-report measure that is modeled on the Yale-Brown Obsessive Compulsive Scale. The Acquisition and Saving Version indexes the severity of hoarding thoughts and behaviors and the subsequent interference and avoidance. Questions address time spent, distress, interference, and effort and success in resisting thoughts and hoarding behaviors. Finally, the Activities of Daily Living-Hoarding Subscale is a 16-item inventory designed to assess interference in daily activities such as bathing, dressing, and preparing and cooking food due to clutter within the home. Items also assess general conditions within the home such as the presence of rotten food and associated safety/health issues (fire hazard, unsanitary conditions). The Activities of Daily Living-Hoarding Subscale is particularly useful when completed by two raters (e.g., by the hoarder and family member or clinician), as discrepancies between the two ratings can be indicative of poor insight.

Poor insight poses a problem for the assessment of hoarding when using measures that rely on self-disclosure of beliefs and behaviors. As noted previously, individuals with compulsive hoarding demonstrate limited recognition of the problem, with up to 50% failing to recognize their behaviors as being problematic. The validity of self-report inventories may, therefore, be compromised. In an effort to address this concern, Frost et al. developed a pictorial measure to index the extent of clutter within the home. The Clutter Image Rating includes nine pictures that vary in rating from 1 (no clutter) to 9 (severe clutter) for a kitchen, a living room, and a bedroom, with a mean composite score calculated across the three rooms (range 1–9). Respondents select the picture that most closely matches the amount of clutter in the corresponding room of their home.

In line with the development of criteria for HD, researchers have developed two diagnostic interviews for HD. The Hoarding Rating Scale (HRS) is a brief 5-item measure that can be administered in interview or questionnaire format. Individuals are asked to rate the severity of acquiring, clutter, difficulty discarding, emotional distress, and life impairment on a scale ranging from 0 (not difficult) to 8 (extremely difficult). The HRS demonstrates good convergent validity with DSM-5 criteria for HD. The Structured Interview for Hoarding Disorder is a comprehensive diagnostic instrument that assesses the extent to which an individual meets each of the DSM-5 criteria and specifiers. The Structured Interview for Hoarding Disorder provides an algorithm for differentiating HD from hoarding related to neurological disease or lesion, OCD, or autism spectrum disorder (ASD), and also contains a risk assessment framework to help the assessor identify immediate threats to health and safety in the individual’s home.