A recent review commissioned by the DSM-5 Anxiety, Obsessive-compulsive Spectrum, Post-traumatic, and Dissociative Disorders Work Group recommended the addition of Hoarding Disorder (HD) as a separate diagnostic entity (1
). Hoarding is characterized by excessive acquisition of and difficulty discarding possessions, resulting in severely cluttered living spaces (2
). It has a high prevalence rate of 2–5% (3
), and the resulting cluttered home environment can lead to health code violations, eviction, fire, family strain, significant cost to the community, and even death (6
Because hoarding has previously been considered a subtype of OCD, much of the research on hoarding has used samples drawn from patients seeking treatment at OCD specialty clinics. However, reviews of accumulating evidence have led to conclusions that the two are distinct disorders (1
). Since most large sample studies are of hoarding within the context of OCD, our understanding of the diagnostic placement and comorbidity of hoarding is limited. To underscore this concern, in the few studies in which participants were solicited for hoarding rather than OCD symptoms, non-hoarding OCD was diagnosed in only a small number of cases (5
). Because of the small number of cases in these studies, the prevalence of OCD in people with hoarding disorder is not yet clear.
An additional limitation in the research on hoarding is the reliance on inadequate definitions and measures of the construct (8
). Not surprisingly, the variability in assessment has resulted in wide variability in reported comorbidities. Several studies failed to find increased risk for any axis I disorder in OCD patients who reported hoarding (11
), while the majority of studies have shown increased comorbidity for selected disorders.
Recent advances in definition (1
) and measurement (9
) provide the ability to more reliably diagnose and assess comorbidity in HD; however, studies using these improved assessment strategies have used small samples. The majority of studies of hoarding comorbidity have reported very high rates of depression, often significantly greater than among OCD comparison groups (13
). Hoarding behaviors have been observed in anxiety disorders other than OCD, especially generalized anxiety disorder (GAD) and social phobia (22
). Among hoarding patients with OCD, rates of these disorders have exceeded nonhoarding OCD in some studies (16
), while the opposite pattern has been found in studies of patients solicited for hoarding and not OCD (13
). Interestingly, Pertusa et al. (17
) reported higher rates of GAD in OCD cases (with or without hoarding) compared to HD cases without OCD, whereas higher rates of social phobia occurred in all HD cases, regardless of accompanying OCD. That is, GAD seemed more strongly associated with OCD, whereas social phobia was more strongly associated with hoarding. Despite apparently elevated rates of traumatic events in hoarding cases (15
), rates of comorbid posttraumatic stress disorder (PTSD) among patients reporting hoarding have been equal to or lower than rates for other anxiety disorders in most studies, ranging from 0–23% (13
Hoarding has been thought to be associated with impulse control problems, particularly those characterized by acquisition such as compulsive buying, kleptomania, and the excessive acquisition of free things (4
). Frost et al. (26
) found that over half of hoarding cases had clinically significant compulsive buying, and when the tendency to excessively acquire free things was included, 86% had at least moderate acquisition problems. Similarly, Mueller et al. (4
) found that nearly two-thirds of hoarding individuals suffered from compulsive buying. To date, however, there are no data on acquisition problems in a large, carefully-diagnosed sample of people with HD. While kleptomania has been reported anecdotally among people with hoarding problems (27
) and found to be associated with hoarding behaviors in a nonclinical sample (28
), as yet, no data have linked the two clinical conditions. Rates of attention deficit-hyperactivity disorder (ADHD) among hoarding samples have exceeded that of nonclinical groups (29
) and often exceeding that of people with OCD and other clinical comparison groups (29
). Tolin and Villavicencio (32
) reported that inattentive ADHD symptoms, but not hyperactivity, predicted severity of hoarding after controlling for negative affect.
Hoarding has been associated with a wide variety of personality disorders as well. The most frequent finding has been that hoarding is associated with obsessive compulsive personality disorder (OCPD), and in some cases even when the hoarding criterion is excluded (5
). However, studies using hoarding samples not drawn from OCD patients have failed to find elevated rates of OCPD when the hoarding criterion was excluded (17
). Other personality disorders have sometimes, but not routinely, been found to be associated with hoarding.
Reports of gender differences in hoarding comorbidity have been mixed. Labad et al. (34
) found no gender differences in hoarding frequency among OCD patients, whereas Wheaton et al. (21
) reported greater OCD symptom severity among women with versus without hoarding, although no such differences emerged among men. In contrast, Samuels et al. (23
) found higher frequencies of most types of obsessions and several compulsions in men with hoarding-related OCD compared to men with non-hoarding OCD. Among women, only symmetry obsessions and ordering compulsions were more frequent in hoarding than non-hoarding OCD patients. No studies have reported on gender differences in samples recruited for hoarding. Because of the inconsistencies in the findings and the narrow population from which these samples were drawn (OCD patients), no clear hypotheses regarding gender can be made with respect to comorbidity.
The present study employs the largest sample to date of participants solicited solely for hoarding symptoms and using diagnostic criteria for hoarding disorder that match those currently proposed for DSM-5 (1
). This study also solicited participants regardless of their interest in treatment and utilized well-validated measures of hoarding and other symptoms. Comorbidity was compared across participants with HD and participants with OCD without hoarding. Based on previous research, we predicted that:
- A minority of individuals with HD will be diagnosed with OCD.
- Major depressive disorder will be the most frequent diagnosis in both groups and significantly more frequent in HD than OCD participants.
- GAD and social phobia will be diagnosed in HD participants at least as frequently as OCD.
- Frequency of traumatic events but not PTSD will be greater among HD than OCD participants.
- Acquisition-related impulse control problems (compulsive buying, excessive acquisition of free things, kleptomania) will be more frequent in HD than OCD participants.
- Inattentive ADHD, but not hyperactivity, will occur more frequently in HD than OCD participants.
- OCPD will occur more frequently in HD than OCD, but not when the hoarding criterion is removed.
No gender differences were hypothesized, but exploratory analyses of gender were conducted.