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Acquisition in hoarding appears to have impulsive features likely to be evident in behavioral impulsivity and response inhibition. This study used a multi-dimensional model of impulsivity to examine this construct in participants with hoarding (n=32) and anxiety disorders (n=32) who received a diagnostic assessment and completed self-report forms and neuropsychological tasks measuring impulsivity. A diagnosis of hoarding predicted higher levels of self-reported urgency, as well as greater difficulties with response inhibition and lowered adaptive and maladaptive risk taking, independent of social phobia, generalized anxiety disorder and major depressive disorder. However, when age was controlled, hoarding ceased to predict these outcomes independent of other psychiatric diagnoses. Although specific symptoms of hoarding appeared significantly related to some aspects of impulsivity, analyses indicated that age accounted for these findings. In the present study, as in other studies, hoarding participants averaged approximately 25 years older than those with anxiety disorders, rendering examination of response inhibition and risk taking in hoarding versus anxiety disorders more difficult. Further research on other aspects of impulsivity (e.g., reward delay, planning/foresight) in hoarding and other psychiatric conditions with age matched comparison samples can advance understanding of these disorders and potentially lead to innovative treatments.

Hoarding is a condition characterized by significant difficulty discarding ordinary possessions, as well as excessive clutter in one's home that frequently results in impairment and/or distress (Frost et al., 2011 and Tolin et al., 2010). Until recently, it had been assumed that hoarding was a subtype of obsessive–compulsive disorder (OCD) (Abramowitz et al., 2008, Coles et al., 2003 and Pertusa et al., 2008). However, hoarding has often predicted limited or poor treatment response to traditional interventions for OCD (Abramowitz et al., 2003, Mataix-Cols et al., 1999 and Mataix-Cols et al., 2005). Studies of hoarding have shown a phenomenological, neurobiological, and genetic profile separate from OCD, and experts in the field have recently proposed criteria for the possible inclusion of hoarding as an independent disorder in the upcoming DSM-5 (Abramowitz et al., 2008, Frost et al., 2011, Mataix-Cols et al., 2010, Pertusa et al., 2008 and Pertusa et al., 2010). Diagnostic classification and treatment development would be aided by continued investigation into the distinctive core aspects of hoarding that are not well understood. One such understudied area is excessive acquisition, a characteristic of hoarding that appears to be highly prevalent and have debilitating effects (Frost, Tolin, Steketee, Fitch, & Selbo-Bruns, 2009). Previous studies have suggested that up to 15% of those with hoarding problems deny having difficulties with excessive acquisition (Frost et al., 2009) accordingly, excessive acquisition has been proposed as a specifier as opposed to a diagnostic criterion for hoarding disorder (Frost, Steketee, & Tolin, 2012). Additionally, excessive acquisition in hoarding has been associated with a greater severity of hoarding symptoms, as well as higher levels of impairment (Frost et al., 2009). In a recent study of 216 hoarders, Frost et al. (2011) found 78.3% of the sample met criteria for one or more acquisition related impulse control problems including buying, acquisition of free items, and kleptomania. More women than men with hoarding met criteria for compulsive buying (64.8 versus 48%), although the odds ratio for acquisition related impulse control disorders was larger in men versus women (Frost et al., 2011). The undeniable presence of excessive acquisition in hoarding has led to the suggestion that there is considerable diagnostic overlap between hoarding and impulse control disorders (Steketee & Frost, 2003). It has been noted that excessive acquisition in hoarding frequently appears to be ego-syntonic and driven by negative and pleasurable emotional states, similar to other disorders on the impulse control spectrum (Steketee & Frost, 2003). Researchers have proposed that a number of disorders (including OCD, Tourette's, Body Dysmorphic Disorder, trichotillomania, attention deficit hyperactivity disorder, pathological gambling. and substance addictions) are composed of both core impulsive and compulsive characteristics (Fineberg et al., 2010). Impulsive and compulsive disorders have typically been conceptualized at opposite ends of a spectrum with impulsive disorders focused on reward seeking and compulsive disorders focused on harm avoidance (Fineberg et al., 2010 and Hollander and Wong, 1995). However, more recently these disorders have been proposed as having similarities in the dysregulation of fronto-striatal circuits that result in behavioral disinhibition (Fineberg et al., 2010 and Van de Huevel et al., 2010). It has also been suggested that a number of these disorders may be characterized by reward processing difficulties stemming from abnormal meso-limbic dopaminergic functioning (Fineberg et al., 2010). Subsequently, it has been suggested that impulsivity and compulsivity may be orthogonal to one another and present themselves in these disorders in differing levels (Fineberg et al., 2010). While several studies of hoarding have investigated the presence of impulsive features, none of the studies using clinical hoarding samples have assessed facets of impulsivity using a multi-dimensional model. A multi-dimensional model of impulsivity encompasses several factors of the construct at the same time, allowing for an assessment in which potentially important aspects are not overlooked. The majority of studies in hoarding have examined deficits in response inhibition, constituted generally by an inability to inhibit an already activated motor response (Aron & Poldrack, 2005) as well as reward processing difficulties using a Go/No-Go task and a form of the Iowa Gambling Task (IGT). Grisham, Brown, Savage, Steketee, and Barlow (2007) found that individuals with hoarding had greater difficulty inhibiting prepotent responses on the Connors Continuous Performance Test, as compared to those with non-hoarding OCD and anxiety disordered controls. These results were significant even after controlling for depression, other OCD symptoms, and schizotypy. However, Grisham et al. (2007) failed to find group differences on performance on the IGT. In another study by Grisham, Norberg, Williams, Certoma, and Kadib (2010) there failed to be significant differences in impulsivity on an Affective Go/No Go task (response inhibition) and on the Cambridge Gambling Task (CGT) (risk taking) between 19 hoarding, 17 clinical anxiety and mood disorder, and 20 healthy control participants. Tolin, Villavicencio, Umbach, and Kurtz (2011) also found no significant differences on the number of commission errors made on the CPT across hoarding (n=27), OCD non-hoarding (n =12) and healthy control (n=26) groups. After subjective distress, impulsivity is perhaps the most common diagnostic criterion found across disorders in the DSM-IV and has been frequently cited as an etiological factor in many models of psychopathology ( Gay et al., 2008 and Whiteside and Lynam, 2001). However, conceptualization of impulsivity as a psychological construct has been inconsistent, and research examining impulsivity has differed widely in definition and measurement across studies. A broad definition of impulsivity is action without foresight ( Winstanley, Eagle, & Robbins, 2006) and a more specific definition has been, “a range of actions that are poorly conceived, prematurely expressed, unduly risky, or inappropriate to the situation and that often result in undesirable consequences ( Daruna & Barnes, 1993).” Commonly used self-report measures suggest that there are multiple dimensions of impulsivity that reflect general themes of poor inhibitory control, inability to delay for reward and lack of planning/foresight when making decisions ( Winstanley et al., 2006). One of the more comprehensive and accepted models of impulsivity, Barratt's (1959) model postulates three higher order facets of impulsivity (attentional, motor and non-planning) based on the integration of medical, behavioral, psychological and social models (Whiteside & Lynam, 2001). Whiteside and Lynam (2001) examined the relationship of impulsivity to elements in the Five Factor Model: impulsiveness, excitement seeking, self-discipline, and self deliberation. Factor analysis produced a four-factor solution: Urgency, (lack of) Perseverance, (lack of) Premeditation, and Sensation Seeking, labeled the UPPS Impulsive Behavior scale which is frequently used in impulse control disorder samples (Whiteside and Lynam, 2003 and Whiteside et al., 2005). The scale's four facets successfully predicted differential outcomes of impulsivity in a community sample, including aggression (urgency), antisocial behavior (sensation seeking, lack of premeditation), substance use (lack of premeditation), inattention (lack of perseverance), hyperactivity/impulsivity (premeditation), and attention-deficit hyperactivity disorder and eating disorder symptoms (urgency) (Whiteside & Lynam, 2003). The scale has also been used in a variety of samples including substance abuse, pathological gambling, obesity, personality disorders, and neuropsychiatric conditions such as Alzheimer's disease (Gay et al., 2008). Urgency, defined as the tendency to respond with strong impulses under the condition of negative affect and associated with the impulsiveness facet of the Neuroticism Extraversion Openness-Personality Inventory-Revised (NEO-PI-R), has stood out in particular for its association with various impulse control psychopathologies including bulimia, insomnia, substance abuse and compulsive buying (Billieux et al., 2010 and Gay et al., 2008). A recent cross-cultural investigation by Timpano et al. (2013) found that a multi-dimensional model of impulsivity predicted hoarding in two separate non-clinical samples. The Barratt Impulsivity Scale total score (BIS-11) predicted self-reported hoarding symptoms (acquisition and clutter) in a non-clinical US sample, even after controlling for comorbid mood, anxiety and substance use symptoms. Timpano et al. (2013) also found that Urgency and lack of Perseverance on the UPPS Impulsive Behavior scale predicted hoarding severity in a separate German non-clinical sample. The Urgency subscale was associated with all three symptoms of hoarding (e.g. clutter, difficulties discarding and acquisition) and (lack of) Perseverance predicted difficulty discarding. This study emphasizes the need for further investigation of impulsivity in clinical samples of hoarding with the use of a multi-dimensional model. Age is a potentially important variable in such investigations as previous research indicates that normal aging processes are associated with cognitive decline (West, 1996). Older age has been associated with greater deficits in response inhibition (Treitz et al., 2007 and Wecker et al., 2000). Research on risk taking has been less clear with some research showing no age differences on cognitive paradigms (Dror et al., 1998 and Zamarian et al., 2008) and others demonstrating that older age is associated with more conservative strategies (Deakin, Aitken, Robbins, & Sahakian, 2004). The present study explored impulsive features among people with clinically significant hoarding using a multi-dimensional assessment to examine whether some aspects of impulsivity are more strongly associated with hoarding symptoms than others. A comprehensive understanding of impulsive features could improve diagnostic classification and contribute to the advancement of etiological and intervention research. The present investigation compared hoarding and mixed-anxiety disorder samples on self-report and neuropsychological measures, taking age into account. Those with hoarding were hypothesized to score significantly higher than those with anxiety disorders on all dimensions of impulsivity including Urgency, (lack of) Premeditation, (lack of) Perseverance and Sensation Seeking, as well as on neuropsychological measures associated with the constructs of Urgency, (lack of) Perseverance and Sensation Seeking.