Behaviour Research and Therapy 45 (2007) 1471–1483 Neuropsychological impairment associated with compulsive hoarding Jessica R. Grisham a, , Timothy A. Brown b , Cary R. Savage c , Gail Steketee b , David H. Barlow b a University of New South Wales, Australia b Boston University, MA, USA c University of Kansas, KS, USA Received 21 September 2006; received in revised form 19 December 2006; accepted 19 December 2006 Abstract A group of patients with compulsive hoarding (n ¼ 30) was compared to a mixed clinical group (n ¼ 30) and a nonclinical community group (n ¼ 30) on laboratory tests of information-processing features hypothesized to be central to hoarding (memory, attention, and decision-making). Hoarding patients demonstrated slower and more variable reaction time, increased impulsivity, greater difficulty distinguishing targets and nontargets, and worse spatial attention relative to comparison groups. Multiple regression analyses demonstrated that slower reaction time and increased impulsivity were significantly related to hoarding symptoms over and above the effect of depression, schizotypy, and other obsessive- compulsive disorder (OCD) symptoms. There were no group differences on a test of emotion-based decision-making. Results are discussed in terms of previous findings and theoretical models of compulsive hoarding. r 2007 Elsevier Ltd. All rights reserved. Keywords: Compulsive hoarding; Obsessive-compulsive disorder; Saving; Attention; Executive functioning Neuropsychological impairment associated with compulsive hoarding syndrome Compulsive hoarding is characterized by the accumulation of and failure to discard a large number of seemingly useless possessions, resulting in living spaces too cluttered to be used for their intended purposes (Frost & Hartl, 1996). Hoarding has been reported in a variety of psychiatric disorders and its diagnostic classification is controversial. Although it is listed as one of the eight criteria for obsessive-compulsive personality disorder (OCPD) in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorder (DSM-IV; American Psychiatric Association, 1994), research suggests that the defining features of OCPD are not strongly nor specifically associated with the personality characteristics of those with compulsive hoarding (Frost, Steketee, Williams, & Warren, 2000; Mataix-Cols, Baer, Rauch, & Jenike, 2000; Winsberg, Cassic, & Koran, 1999). ARTICLE IN PRESS www.elsevier.com/locate/brat 0005-7967/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.brat.2006.12.008 Corresponding author. Tel.: +61 2 8382 1727; fax: +61 2 8382 1721. E-mail address: [email protected] (J.R. Grisham).
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Behaviour Research and Therapy 45 (2007) 1471–1483
Neuropsychological impairment associated with compulsive hoarding syndrome
Compulsive hoarding is characterized by the accumulation of and failure to discard a large number ofseemingly useless possessions, resulting in living spaces too cluttered to be used for their intended purposes(Frost & Hartl, 1996). Hoarding has been reported in a variety of psychiatric disorders and its diagnosticclassification is controversial. Although it is listed as one of the eight criteria for obsessive-compulsivepersonality disorder (OCPD) in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorder
(DSM-IV; American Psychiatric Association, 1994), research suggests that the defining features of OCPD arenot strongly nor specifically associated with the personality characteristics of those with compulsive hoarding(Frost, Steketee, Williams, & Warren, 2000; Mataix-Cols, Baer, Rauch, & Jenike, 2000; Winsberg, Cassic, &Koran, 1999).
e front matter r 2007 Elsevier Ltd. All rights reserved.
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Most contemporary investigators conceptualize hoarding as a symptom or subtype of obsessive-compulsivedisorder (OCD) due to significant frequencies of hoarding symptoms among OCD patients, ranging from 18%to 33% (Frost, Krause, & Steketee, 1996; Rasmussen & Eisen, 1989; Samuels et al., 2002). Wu and Watson(2005), however, argued against the inclusion of hoarding within OCD after finding strong intercorrela-tions for classic OCD symptoms such as checking, rituals, and contamination and only moderate correlationsbetween these symptoms and hoarding. In addition, hoarding is associated with poor treatment responseto pharmacological and behavioral treatments that are efficacious for OCD (Abramowitz, Franklin,Schwartz, & Furr, 2003; Black et al., 1998; Mataix-Cols, Marks, Greist, Kobak, & Baer, 2002; Winsberg et al.,1999).
Improved understanding of neural and neuropsychological characteristics of compulsive hoarding willinfluence its placement within the DSM nosology and guide efforts to improve treatment for hoarding. Severalcase reports have described cases of pathological collecting and saving that began after a brain injury, typicallyalong with other changes in personality and social functioning (Eslinger & Damasio, 1985; Hahm, Kang,Cheong, & Na, 2001). In addition, two recent studies have investigated a possible neural basis of compulsivehoarding. In the first study using positron emission technology (PET) to examine compulsive hoarding,Saxena et al. (2004) found that compared to nonhoarding OCD patients, OCD patients with compulsivehoarding had significantly lower glucose metabolism in the dorsal anterior and posterior cingulate gyrus. Inanother study conducted by Anderson, Damasio, and Damasio (2005), 13 of 86 patients with focal lesionsexhibited abnormal collecting behavior. All 13 of these patients had damage to the mesial frontal region of thebrain, including the anterior cingulate.
According to the cognitive-behavioral model of hoarding (Frost & Gross, 1993; Frost & Hartl, 1996),individuals who hoard may have information processing problems in the areas of attention, categorization,memory, and decision-making ability. The attention problems and inability to sustain motivation commonlyexhibited by individuals with compulsive hoarding may result from impaired executive functioning. Poor self-regulation and difficulty suppressing responses evoked by the environment may contribute to excessiveacquisition and saving behavior, while problems with planning and executing complex, goal-directed motorresponses and controlling interference may limit these individuals’ ability to effectively organize and discardtheir possessions.
Despite myriad neuropsychological studies of OCD (for a review, see Greisberg &McKay, 2003), only a fewstudies have examined neuropsychological difficulties specifically associated with compulsive hoardingsymptoms. These studies have provided initial support for the hypothesized deficits. Hartl et al. (2004) foundthat hoarding participants were impaired relative to comparison participants on organization and delayedrecall of visual information on the Rey-Osterrieth Complex Figure Test (RCFT; Osterrieth, 1944) and onshort and long-delayed recall measures of verbal information on the California Verbal Learning Test (CVLT;Delis, Kramer, Kaplan, & Ober, 1987). Other studies have found that hoarding is associated with increasedsymptoms of Attention Deficit Hyperactivity Disorder (ADHD; Hartl, Duffany, Allen, Steketee, & Frost,2005) and deficits in the categorization and organization of information (Wincze, Steketee, & Frost, 2007).Finally, Lawrence et al. (2006) found that compared to OCD patients without hoarding symptoms, OCDpatients with hoarding symptoms demonstrated impaired decision-making on the Iowa Gambling Test (IGT;Bechara, Damasio, Damasio, & Anderson, 1994). In contrast with these positive findings, Simpson et al.(2006) found that self-reported OCD symptom dimensions, including hoarding, were not significantly relatedto performance on neuropsychological tasks of executive functioning, nonverbal memory, and motor speed.No laboratory study thus far, however, has used laboratory procedures to investigate proposed attention anddecision-making impairment among a group of individuals whose primary psychiatric symptom is compulsivehoarding.
In the current study of compulsive hoarding, the specific cognitive abilities of interest were verbal andnonverbal attention, working memory, response inhibition, and decision-making. Because of the controversialdiagnostic status of hoarding, we recruited participants whose most severe psychiatric symptom wascompulsive hoarding and allowed other comorbid psychiatric symptoms, including other OCD symptoms, tonaturally covary. Individuals without any anxiety or mood disorders served as a community comparisongroup. In addition, because anxiety and depression are known to interfere with cognitive functioning(Eysenck, 1991), a clinical comparison group of individuals with anxiety and mood disorders (excluding OCD
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and hoarding) was included to clarify whether any performance deficits demonstrated by the hoarding groupwere associated with anxiety and mood disorders in general.
The present study sought to test a model of impaired executive functioning associated with compulsivehoarding in a relatively inclusive sample of hoarding patients using self-report measures and laboratory tests.We hypothesized that certain neuropsychological deficits would contribute to hoarding behavior. Our primaryhypotheses were that (a) despite demonstrating comparable intelligence, individuals with hoarding problemswould report more symptoms of ADHD and perform more poorly on tests of verbal and nonverbal sustainedattention, memory, and response inhibition than clinical and community comparison participants, (b) poorperformance on the neurocognitive tasks would predict greater severity of hoarding symptoms, over andabove the effects of other psychiatric symptoms, and (c) compulsive hoarding participants would performmore poorly than clinical and community comparison participants on a test of reasoning and decision-making, the IGT.
Method
Participants
A total of 90 participants were recruited for this study from the community and from an anxiety and mooddisorders specialty clinic. Diagnoses for participants recruited from the anxiety clinic were established bytrained clinicians using the Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV; Brown, Di Nardo,& Barlow, 1994).
The primary group of interest consisted of 30 individuals whose most prominent, distressing, and impairingpsychiatric symptom was compulsive hoarding. Because no DSM-IV criteria exist for compulsive hoarding,hoarding participants were required to meet the criteria proposed by Steketee and Frost (2003): (a) a largeamount of clutter (possessions kept in a disorganized fashion) in the majority of living areas of the home, (b)difficulty discarding items, even those of apparently useless or limited value, (c) current or past compulsiveacquiring through excessive buying or collecting free items that are not needed and/or not affordable, (d) thebehaviors or clutter caused either marked distress or interference with functioning (e.g., occupational/school,family and social activities, or significant health or safety risk), (e) clutter persisting for at least 6 months, and(f) hoarding behaviors not better accounted for by another mental disorder (e.g., dementia, bipolar disorder,major depressive disorder).
Because hoarding is listed as an OCD symptom in the ADIS-IV, all of the hoarding participants received aprincipal diagnosis of OCD according to this interview, with hoarding endorsed as the most severe symptom.Among these participants, 56.7% (n ¼ 17) reported at least one clinically significant obsession or compulsionin addition to compulsive hoarding. Two-thirds of the compulsive hoarding sample received one or moreadditional axis I diagnoses: 33.3% (n ¼ 10) received a diagnosis of social phobia, 26.7% (n ¼ 8) received adiagnosis of major depressive disorder, 13.3% (n ¼ 4) received a diagnosis of generalized anxiety disorder, and10% (n ¼ 3) received a diagnosis of panic disorder with agoraphobia. In addition, 6.7% (n ¼ 2) were assignedthe following diagnoses: posttraumatic stress disorder, dysthymic disorder, bipolar disorder, or specificphobia. Finally, 3.3% of the sample (n ¼ 1) were assigned the following diagnoses: impulse control nototherwise specified, agoraphobia without panic, somatoform disorder not otherwise specified, or cyclothymicdisorder.
A community comparison group and a clinical comparison group were also recruited. The communitycomparison group comprised 30 individuals without a current mood or anxiety disorder. The clinicalcomparison group consisted of 30 individuals with a current mood or anxiety disorder other than OCD.Principal diagnoses for the clinical comparison group were as follows: 43.3% (n ¼ 13) received a diagnosis ofsocial phobia, 16.7% (n ¼ 5) received a diagnosis of major depressive disorder, 13.3% (n ¼ 4) received adiagnosis of panic disorder with agoraphobia, 10% (n ¼ 3) received a diagnosis of generalized anxietydisorder, and 6.7% (n ¼ 2) received a diagnosis of posttraumatic stress disorder. Finally, 3.3% (n ¼ 1) of thesample received the following diagnoses: panic disorder without agoraphobia, agoraphobia without panic,and anxiety disorder not otherwise specified.
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The exclusionary criteria for all groups included active psychosis, current substance or alcohol abuse ordependence, past alcohol or substance dependence, current suicidality, and current homicidality. Individualsin the clinical comparison group were not excluded for subclinical hoarding symptoms, allowing for a fullrange of hoarding and other Axis I symptoms when the clinical and hoarding groups were combined forstatistical analyses.
Persons recruited to participate in the comparison groups were matched to the hoarding group with respectto age, gender, and handedness due to the potential effect of these characteristics on neuropsychologicalperformance. The three groups did not differ significantly on other relevant demographic characteristics,including race, employment status, years of education completed, marital status, or religion. See Table 1 forbasic demographic information by group.
Diagnostic assessment
Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV; Brown et al., 1994): The ADIS-IV is a semi-structured interview designed to diagnose anxiety, mood, somatoform, and substance use disorders and toscreen for the presence of other conditions (e.g., psychosis). Compulsive hoarding is listed as a compulsionwithin the OCD section of the ADIS-IV. In addition, five questions specifically addressing the compulsivehoarding criteria (Frost, Steketee, Tolin, & Renaud, under editorial review) were added as a supplement to theADIS-IV. The ADIS-IV has produced good-to-excellent reliability estimates for the majority of anxiety andmood disorders (e.g., r ¼ .84 for the clinical severity rating of OCD; Brown, Di Nardo, Lehman, & Campbell,2001). All of the diagnosticians who participated in this study underwent extensive training and met strictcertification criteria in the administration of the ADIS (see Brown et al., 2001 for a detailed description ofthese procedures).
Self-report questionnaires
ADHD Symptom Checklist (ADHD-CL; Barkley & Murphy, 1998): This adult symptom checklist is a self-report questionnaire on which respondents rate the intensity of ADHD symptoms on a 4-point Likert scale,ranging from 0 (never or rarely) to 3 (very often). Checklist scores include the sum of ratings on the total scale,inattention items, and hyperactive-impulsive items. Internal consistency (coefficient alpha) of the checklist is.97 (Barkley & Murphy, 1998).
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Beck Anxiety Inventory (BAI; Beck, Epstein, Brown, & Steer, 1988): The BAI is a 21-item self-reportinventory of symptoms of anxiety. The BAI’s reliability, convergence with other anxiety measures, anddiscriminant validity have been well supported (Beck & Steer, 1993).
Beck Depression Inventory (BDI; Beck, 1987): The BDI is a widely used measure of depression that hasbeen shown to be internally consistent, reliable, and valid in both psychiatric and normal populations (Beck,Steer, & Garbin, 1988).
Obsessive-Compulsive Inventory (OCI; Foa, Kozak, Salkovskis, Coles, & Amir, 1998): The OCI is a 42-itemself-report measure of OCD symptoms containing 7 subscales: doubting, checking, hoarding, neutralizing,obsessing, ordering, and washing. Symptom frequency is scored on a 5-point Likert-type scale that rangesfrom 0 (never) to 4 (almost always). Subscale scores range from 0 to 4 and represent the mean rating for thatsubscale. Coefficient alphas for these seven subscales ranged from .74 to .85 in the original control sample; thetotal score alpha was .94. Subscales showed good test-retest reliability and convergent validity with othermeasures of OCD symptoms in a clinical sample (Foa et al., 1998).
Personality Disorder Questionnaire-4, Schizotypal Personality Disorder Subscale (PDQ-4 SPD; Hyler, 1997):The PDQ-4 is a self-report inventory with a true/false response format that assesses the personality disordersincluded in the DSM-IV. The Schizotypal Personality Disorder subscale is comprised of 9 items from the PDQthat assess schizotypal personality disorder. This measure was included due to findings suggesting thatneurocognitive deficits, particularly working memory deficits, are associated with schizotypy (for a review, seePark & Lee, 2002), as well as findings of increased Axis II pathology associated with compulsive hoarding(Frost et al., 2000).
Saving Inventory-Revised (SI-R; Frost, Steketee, & Grisham, 2004): The SI-R is a 23-item questionnairewith 3 factor analytically defined subscales for difficulty discarding, excessive clutter, and compulsiveacquisition. It has shown good internal consistency and test–retest reliability, as well as known-groups validityand concurrent and divergent validity in clinical and nonclinical samples (Frost et al., 2004).
Neuropsychological tests
Digit Span (DS; Wechsler, 1997): DS is a test from the Wechsler Adult Intelligence Scale-Third Edition(WAIS-III; Wechsler, 1997). It is considered to be a test of short-term auditory memory and attention ofsimple information. The participant must recall and repeat auditory information in the proper sequence(forwards and backwards). For DS backwards, the participant must hold the memory longer and transform itprior to making a restatement. DS has a test–retest reliability of .83 and a split-half reliability of .90 (Wechsler,1997).
Visual Memory Span (VMS; Wechsler, 1987): VMS is a test of spatial attention and working memory fromthe Wechsler Memory Scale-Revised (WMS-R; Wechsler, 1987). The participant must repeat tappingsequences of increasing length backwards and forwards. VMS has an average internal consistency of .81(Wechsler, 1987).
Wechsler Abbreviated Scale of Intelligence Subtests (WASI; Psychological Corporation, 1999): WASIsubtests were used to provide estimates of verbal and nonverbal intelligence. WASI Vocabulary: This subtest isa 42-item task similar to the Vocabulary subtest of the WAIS-III (Wechsler, 1997). The reliability coefficientsfor the Vocabulary subtest range from .90 to .98 (Psychological Corporation, 1999). WASI Matrix Reasoning
(WASI-MR): WASI-MR is comprised of 35 incomplete visual patterns that are used to assess nonverbal fluidreasoning and general intellectually ability. The reliability quotient for WASI-MR ranges from .88 to .96(Psychological Corporation, 1999).
The Conners’ Continuous Performance Test II (CPT-II; Conners, 2000): The CPT-II is a computer-basedtest of sustained attention that measures consistency of performance and the ability to suppress impulsiveresponses. The CPT-II has demonstrated highly satisfactory test-retest reliability, as well as known-groupsvalidity (Conners, 2000). Participants observe letters that appear rapidly on a computer monitor and press amouse button for every target (letter that is not an X). The CPT-II measures errors of omission, errors ofcommission, signal detectability (d prime), response style (Beta), and hit reaction time (HRT). The CPT-IIsoftware applies a discriminant function analysis to provide an overall indication as to whether the profileobtained from the respondent best fits a clinical or nonclinical pattern of ADHD or neurological impairment
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and calculates a Confidence Index to estimate the degree of fit. For example, an ADHD Confidence Index of65% indicates that the fit to a clinical ADHD profile is made with 65% confidence.
IGT (Bechara et al., 1994): This computerized card playing game designed by Bechara and colleagues wasused to assess emotion-based decision-making. The player is instructed to try to win as much money aspossible over 100 selections from one of four decks. The task attempts to simulate the decisions made in reallife in terms of reward, punishment, and uncertainty of outcomes. The decks are labeled A, B, C, and D at thetop end of each deck. The participant should learn that two of the decks are ‘‘high risk’’ (i.e., intermittentlyproduce large rewards but in the long term produce significant losses), whereas two decks lead to small butconsistent gains. Individuals who can use information flexibly to make decisions learn to avoid the risky decks.
Procedure
Compulsive hoarding and clinical comparison participants were recruited shortly after they completed adiagnostic intake assessment or follow-up assessment at an anxiety and mood disorders specialty clinic.Community participants were recruited through newspaper advertisements in several local newspapers andthrough internet advertisements on a free community website. After undergoing a brief phone screeningprocess, participants who agreed to participate were mailed questionnaires and a consent form to completeprior to the day of the study. All participants performed a series of neuropsychological tests. To control fororder effects, a partially counterbalanced design was employed. The entire battery took about 2–3 h tocomplete, plus approximately 1 h to complete the self-report questionnaires.
Results
Self-report questionnaires
The three groups were tested together using ANOVA. Follow-up tests were conducted using Student-Newman-Keuls (SNK) post hoc testing. Table 2 summarizes the results from the self-report questionnaires. Asexpected, the compulsive hoarding group reported significantly more hoarding symptoms than the
Table 2
Means and standard deviations for self-report questionnaires (N ¼ 90)
Variable Hoarding M (SD) Clinical M (SD) Community M (SD) F
ADHD-CL: Total 20.0a (11.71) 10.8b (7.74) 4.9c (3.26) 24.99***
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comparison groups on the SI-R. The score of the hoarding group on the SI-R was similar to mean scores (53.7and 62.0) for other samples reporting compulsive hoarding problems (Frost et al., 2004). The hoarding groupalso reported significantly more OCD symptoms than both comparison groups (F(2,87) ¼ 28.17, po.001,Z2 ¼ .39), although the OCI total score of the hoarding group (53.60) appeared somewhat lower than the totalOCI score (66.3) reported in a previously published OCD clinical sample (Foa et al., 1998).
In addition to the hoarding and OCD questionnaires, groups were tested on measures of anxiety,depression, and schizotypy, all of which are known to affect performance on neuropsychological tests(Eysenck, 1991; Park & Lee, 2002). ANOVA revealed a significant main effect of groups on the BAI,F(2,87) ¼ 22.5, po.001, Z2 ¼ .34, the BDI, F(2, 87) ¼ 20.59, po.001, Z2 ¼ .32, and the PDQ-4 SPD,F(2, 87) ¼ 13.88, po.001, Z2 ¼ .24. Post hoc tests indicated that the hoarding and clinical comparison groupsdid not differ with respect to self-reported level of anxiety and that both groups reported significantly moreanxiety than the community comparison group. With respect to depression and schizotypy, post hoc testsrevealed significant differences between each of the three groups on the BDI and the PDQ-4 SPD. On both ofthese measures the hoarding group was the most symptomatic, followed by the clinical comparison group andthe community comparison group.
As predicted, the hoarding group reported significantly more symptoms of ADHD than the comparisongroups on the ADHD-CL. There were significant main effects of groups on the ADHD-CL total score,F(2, 87) ¼ 24.99, po.001, Z2 ¼ .37, the inattention subscale, F(2, 87) ¼ 28.84, po.001, Z2 ¼ .40, and theimpulsivity subscale, F(2, 87) ¼ 13.03, po.001, Z2 ¼ .23. Post hoc tests demonstrated that the hoarding grouphad significantly higher mean scores on the ADHD-CL total score and both subscales than the clinicalcomparison group, which in turn had significantly higher mean scores than the community comparison group.
Neuropsychological tests
Intellectual performance: The three groups were compared on WASI Vocabulary and the WASI–MR.Although ANOVA revealed no significant overall effect of groups on WASI Vocabulary, there was asignificant overall effect of groups on WASI-MR, F(2, 87) ¼ 3.21, po.05, Z2 ¼ .07. A post hoc test (SNK)indicated that individuals in the hoarding group performed significantly worse on WASI-MR than individualsin the community comparison group. There was also a nonsignificant trend (p ¼ .09) indicating that thehoarding group performed worse than the clinical comparison group.
Attention and memory: ANOVA was utilized to compare the three groups on DS, forward and backward,and VMS, forward and backward. There was no significant overall main effect of groups for DS, forward orbackward, or for VMS backward. There was a significant main effect of groups, however, for VMS forward,F(2, 87) ¼ 8.86, po.01, Z2 ¼ .17. Post hoc tests revealed that the hoarding group performed significantly worseon VMS forward than both comparison groups, which suggests decreased spatial attention in this group.
The three groups were also compared on their performance on several indices of attention provided by theCPT-II (see Table 3). ANOVA yielded a significant main effect of groups for both the Confidence Indexfor ADHD, F(2, 87) ¼ 3.69, po.05, Z2
¼ .08 and the Confidence Index for neurological impairment,F(2, 87) ¼ 5.21, po.01, Z2 ¼ .11. Post hoc tests suggested that, as predicted, the hoarding group hadsignificantly higher Confidence Indices for ADHD and neurological impairment than both of the comparisongroups at po.05. There was not a significant difference between the clinical and community comparisongroups on either Confidence Index.
With respect to the specific indices, ANOVA revealed a significant main effect of groups for HRT, F(2, 87) ¼3.37, po.05, Z2 ¼ .07, HRT standard error, F(2, 87) ¼ 4.44, po.05, Z2 ¼ .09, commission errors (responses tostimuli other than the target), F(2, 87) ¼ 4.21, po.05, Z2 ¼ .09, and d prime (signal detectability), F(2, 87) ¼ 3.93,po.05, Z2 ¼ .08. There was no significant main effect of groups for omission errors, perseverations, or Beta(response style). Post hoc testing revealed that the hoarding group had the slowest HRT, which was significantlyslower than the clinical comparison group, although the difference between the hoarding group and thecommunity comparison group did not reach significance at po.05. HRT standard error and commission errors ofthe hoarding group were significantly higher than both comparison groups, suggesting that the hoarding grouphad more variable reactions and were more impulsive. Finally, post hoc tests indicated that individuals in thehoarding group had a significantly lower mean value for d prime than those in the clinical comparison group,
Mean scores on Conners’ Continuous Performance Test by group (N ¼ 90)
Variable Hoarding Clinical Community F
Reaction time
HRT 424.4a 382.6b 399.8a,b 3.37*
HRT SE 7.4a 5.5b 5.9b 4.44*
Variability of SE 10.9 8.5 7.4 1.84
Response style (Beta) .8 2.0 1.2 .95
Accuracy
d prime .8b 1.1a .9a,b 3.93*
Perseverations 1.0 .3 .3 2.63
% Omissions 2.7 1.3 .8 1.66
% Commissions 33.5a 21.5b 24.9b 4.18*
Confidence indices
CI for ADHD 57.1a 48.3b 46.5b 3.69*
CI for NEURO 54.5a 40.1b 41.4b 5.21**
Note: Student-Newman-Keuls post hoc testing was conducted to examine group differences. HRT ¼ Hit Reaction Time; SE ¼ Standard
Error; CI for ADHD ¼ Confidence Index for ADHD; CI for NEURO ¼ Confidence Index for neurological impairment. Means with
different superscripts differ significantly in magnitude (po.05).
*po.05, **po.01.
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suggesting that the hoarding group had poorer detectability of the target stimuli. The difference between thehoarding group and the community comparison approached significance at p ¼ .07.
Given the rate of comorbidity found in the hoarding group, it was important to determine whetherattentional deficits could be attributed to the group as a whole or whether they were only accounted for bythose participants with hoarding who had clinically significant nonhoarding OCD symptoms, schizotypy, anddepression. Further, because the hoarding group had lower spatial intelligence than the community group,additional analyses were necessary to determine if group differences in CPT-II performance were due todifferences in spatial intelligence. Because individuals were not excluded from the clinical comparison groupfor endorsing subclinical hoarding symptoms, the hoarding and clinical comparison groups were combined torepresent a range of hoarding symptoms. Multiple regression analyses were conducted on the combinedclinical sample of compulsive hoarding and clinical comparison participants (n ¼ 60) to evaluate the relationof poor performance on the CPT-II, VMS forward, and WASI-MR to increased hoarding severity controllingfor the effects of clinical variables that may affect performance on neuropsychological tasks, such asdepression, other OCD symptoms, and schizotypy. HRT, commission errors, and omission errors wereselected from the CPT-II as indicators of sustained attention and response inhibition. The CPT-II variable d
prime was excluded due to multicollinearity (multiple R4.80).As a measure of severity of OCD symptoms excluding hoarding, a total score of the 39 OCI items minus the
3 hoarding items was computed (hereafter OCI-NH). The SI-R was entered as the dependent variable andHRT, commission errors, omission errors, VMS forward, WASI-MR, BDI, OCI-NH, and PDQ-4 SPD wereentered simultaneously as independent variables. See Table 4 for zero-order correlations. The modelcontaining all of these variables explained 52% of the variance in SI-R scores (F(8, 51) ¼ 6.80, po.001). HRT(B ¼ .10, Beta ¼ .29, t ¼ 2.29, po.05) and commission errors (B ¼ .87, Beta ¼ .24, t ¼ 2.10, po.05)significantly added to the prediction of hoarding severity, and VMS forward approached significance as apredictor of hoarding (B ¼ �3.00, Beta ¼ �.24, t ¼ 1.98, p ¼ .05). Of the clinical variables, OCI-NH wasfound to be a significant predictor of hoarding (B ¼ .32, Beta ¼ .32, t ¼ 2.25, po.05). Omission errors,WASI-MR, BDI, and the PDQ-4 SPD did not contribute significantly to the model. These results suggestedthat although nonhoarding OCD symptoms are significantly related to hoarding severity, the impulsivity, slowreaction time, and decreased spatial attention in the hoarding group could not be attributed solely todepression, OCD, schizotypy, or lower nonverbal intelligence.
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Table 4
Correlations between hoarding, clinical characteristics, and neuropsychological performance (N ¼ 60)
HRT COM OMI VMS FWD WASI-MR BDI OCI-NH PDQ-4 SPD SI-R
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Additional comparisons were conducted to further investigate whether the hoarding group’s poorperformance on the CPT-II, WASI-MR, or VMS forward was due to depression or nonhoarding OCDsymptoms. The hoarding group was divided into those with a clinical mood disorder (n ¼ 11) and without aclinical mood disorder (n ¼ 19). A t-test revealed no significant between-group differences on any of the CPT-II indices, WASI-MR, or VMS forward. In addition, participants were divided into those with clinicallysignificant nonhoarding OCD symptoms (n ¼ 17) and those without clinically significant nonhoarding OCDsymptoms (n ¼ 13). Again, a t-test revealed no significant between-group differences on the CPT-II indices,WASI-MR, or VMS forward.
Decision-making: To compare the groups’ performance on the IGT, a two-way ANOVA with repeatedmeasures design for the three groups (between group comparison) � total number of cards selected from theadvantageous (C+D) minus the disadvantageous decks (A+B) in each of the five blocks (within comparison)was conducted. Positive numbers indicate advantageous performance and negative numbers indicatedisadvantageous performance. The overall mean net scores and standard errors of the hoarding group, clinicalgroup, and community group were 5.28 (SE ¼ 1.20), 4.73 (SE ¼ 1.20), and 4.30 (SE ¼ 1.20), respectively. Thetwo-way ANOVA revealed a significant effect of blocks, F(4, 85) ¼ 14.42, po.001, but no significant maineffect of groups, F (2, 87) ¼ .14, p ¼ .87. Thus all three groups improved their performance over time byselecting more cards from the advantageous decks, with no significant between-group differences.
Discussion
The primary hypothesis of the current study, that compulsive hoarding patients would exhibit difficultieswith attention and response inhibition compared to clinical and nonclinical comparison participants, waslargely confirmed. The results of this study suggest that compulsive hoarding may be associated with bothdifficulty initiating response (slow, variable reaction time) and inhibiting prepotent responses (morecommission errors). The pattern of results of the hoarding group on the CPT-II also suggests they haddecreased ability to develop a consistent strategy relative to the other groups. In addition, the worseperformance of the hoarding group on some spatial/nonverbal tasks (VMS forward and WASI-MR), withunimpaired performance on DS, VMS backward, and WASI Vocabulary suggested that hoarding may beassociated with decreased nonverbal intelligence and attention, despite intact working memory and verbalintelligence. Neuropsychological weaknesses in sustained attention and spatial ability may contribute to thedifficulties that hoarding patients have staying focused on specific tasks, as well as their difficultiescategorizing and organizing their possessions.
Although there are numerous comparisons in the current study, the consistency with which the hoardinggroup performed more poorly than comparison groups on multiple measures of neuropsychological
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functioning, as well as the medium-to-large effect sizes of group differences, argues against the possibility ofType I error. On measures of spatial ability, sustained attention, response inhibition, and self-report ofADHD symptoms, the hoarding group demonstrated impairment relative to comparison groups. In contrast,there were no measures on which the hoarding group performed better than either of the other two groups.Group differences in sustained attention and impulsivity persisted when controlling for other relevantvariables, including symptoms of OCD, depression, and schizotypy. These results provide preliminaryevidence of an association between hoarding and specific neurocognitive deficits, although they do not allowinference as to whether these deficits are a cause or a consequence of the disorder.
Contrary to hypotheses, the hoarding group had an equivalent performance to both comparison groups onthe IGT. One possible reason for the lack of group differences on the gambling task may have been a ceilingeffect, where the task was not sufficiently difficult to detect group differences in a fairly intelligent and well-educated sample. In addition, the IGT is sensitive to risk-taking, and groups that are known for risk-taking(e.g., substance dependent individuals, psychopaths) are known to perform poorly on the task (e.g., Bechara etal., 2001). Although many hoarding patients demonstrate problems with response inhibition and impulsecontrol, they appear excessively cautious when they report saving a wide variety of items to prevent against anunlikely future event where they may need a certain item. Therefore, it is plausible that once they ascertainedwhich deck was ‘‘risky,’’ they were inclined to stay away from that deck and save their hypothetical money justas they save their possessions.
The findings of the present study regarding decision-making were inconsistent with the finding of Lawrenceet al. (2006) that individuals with OCD with additional hoarding symptoms were impaired on the IGT. Onepossible reason for the discrepancy is differences in study recruitment and sample selection: individuals in thecurrent study reported hoarding as their principal (and in some cases only) OCD symptom, whereas Lawrenceet al. (2006) selected a subgroup of patients with additional hoarding symptoms from a group of patientsdiagnosed with OCD. Although a slight majority of hoarding patients in the current study reported clinicalOCD symptoms in addition to hoarding, a significant portion of them did not. It is possible that patientswhose primary psychiatric symptom is compulsive hoarding have a somewhat different etiology and clinicalpresentation than OCD patients with additional hoarding symptoms.
The finding of increased symptoms of SPD within the compulsive hoarding group is intriguing in light of theevidence of associations between schizotypy and neuropsychological impairment, specifically attentionaldysfunction (Kendler et al., 1991), poor executive functioning (Aycicegi, Dinn, & Harris, 2002), and spatialdeficits (Park & Lee, 2002). Several studies have found that positive SPD symptoms are predictors oftreatment failure in OCD (Baer et al., 1992; Jenike, Baer, Minichiello, Schwartz, & Carey, 1986; Moritz et al.,2004). Further, Matsunaga et al. (2002) found that SPD was more common among OCD patients whoseinsight remained poor even after treatment. Increased schizotypy among hoarding patients may partiallyaccount for their poor insight and inadequate treatment response. Symptoms of SPD would also be consistentwith the increased difficulty with social perceptions and interpersonal relationships that has been observedamong compulsive hoarding patients. In the current study, however, hoarding was significantly associatedwith slower reaction time and increased commission errors over and above the effect of SPD. Future studiesshould further evaluate whether neuropsychological deficits associated with compulsive hoarding are relatedto the increased prevalence of SPD in this population.
Treatment implications
One of the most important conclusions that may be drawn from the current study is that treatmentapproaches to compulsive hoarding should be supplemented with strategies that address co-occurringneuropsychological deficits, such as impaired attention. The most common treatment of ADHD is stimulantmedications, and a recent study found that stimulant treatment improves response inhibition among adultswith ADHD (Aron, Dowson, Sahakian, & Robbins, 2003). Moreover, a recent case study of an individualwho presented with compulsive hoarding along with ADHD and SPD responded well to a treatment regimenof fluvoxamine, amphetamine salts, and risperidone, in addition to behavior therapy (Kaplan & Hollander,2004). The authors suggested that augmentation with stimulants may provide benefits in cases of hoardingwith comorbid ADHD, particularly for symptoms of procrastination. If medication or behavioral treatment is
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successful in ameliorating the cognitive problems that confront hoarding patients, these patients may be betterable to benefit from specific hoarding-related treatment strategies and assignments.
Limitations and future directions
One limitation of the current study was the lack of a screening questionnaire to assess for any history ofneurological problems or medical conditions that may have impacted cognitive function (e.g., Parkinson’sdisease). In addition, we did not include a nonhoarding OCD comparison group, which limits our ability todraw conclusions regarding whether weaknesses in this group are associated with hoarding specifically orOCD more generally. Given the emphasis in this study on a model of neuropsychological deficits contributingto hoarding pathology, we aimed to maintain clinical realism by including hoarding patients with comorbidAxis I conditions or other OCD symptoms. OCD symptoms in the hoarding group were significantly higherthan in the two comparison groups and may have contributed to group differences. Moreover, consistent withfindings that compulsive hoarding is associated with high rates of comorbid mood and anxiety disorders(Frost et al., 2000), many hoarding participants met criteria for secondary Axis I disorders.
A related issue is that we did not assess for Axis II comorbidity other than SPD. It is therefore possible thatdifferences observed between the hoarding and clinical comparison groups are accounted for by the presenceof personality disorders. In addition, although validity studies suggest that the PDQ-4 is a useful screeninginstrument, it should ideally be used in conjunction with a structured interview assessment of personalitydisorders (Trull & Larson, 1994). Because the PDQ-4 SPD was not followed by a clinical interview in thepresent study, our conclusions regarding the presence of SPD are tentative and require replication. Futurestudies would benefit from a complete clinical assessment of Axis II disorders, particularly OCPD and SPD.
Despite these limitations, we made several attempts to address the potential confounding effects ofpsychiatric comorbidity in the hoarding group, particularly secondary anxiety and mood disorders. First, inaddition to the community comparison group, we recruited a mixed clinical comparison group that did notdiffer from the hoarding group with respect to mean anxiety level or prevalence of comorbid disorders. Inaddition, we examined the potential impact of comorbid psychiatric symptoms that differed between groupsby statistically controlling for depression, OCD, and schizotypy severity scores in regression analyses. Theseanalyses demonstrated that the relationship between hoarding and attention problems remained significantover and above the effect of comorbid psychiatric symptoms.
Various lines of evidence strongly suggest that compulsive hoarding is a multifactorial condition that islikely to have multiple etiological pathways and maintaining factors. Further investigation of possiblecognitive deficits associated with this disorder will be crucial to achieving clearer diagnostic conceptualization.Additional research is also needed to investigate whether problems with attention and response inhibition arecontributing to the poor treatment response of hoarding patients and to develop more effective treatment forthis complex syndrome.
References
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Aron, A. R., Dowson, J. H., Sahakian, B. J., & Robbins, T. W. (2003). Methylphenidate improves response inhibition in adults with
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