An investigation of delay and probability discounting in hoarding disorder

Behavioral impulsivity may be a mechanism of hoarding disorder (HD). A commonly used and well-validated measure of impulsivity is the delay and probability discounting task, which consists of making decisions about receiving monetary rewards after varying delay intervals and delivery probabilities. We compared delay and probability discounting and self-reported behavioral impulsivity in 81 patients with a primary diagnosis of HD and 45 nonclinical controls. HD participants completed the impulsivity measures before and after 16 weekly sessions of cognitive-behavioral therapy (CBT), whereas control group participants completed the measures before and after a 16-week waiting period. Despite the fact that self-reported impulsivity was greater in the HD group than the control group, delay and probability discounting did not differ between groups. Additionally, while self-reported behavioral impulsivity improved over the course of CBT in HD participants, delay and probability discounting did not change during treatment. Furthermore, higher delay discounting scores (i.e., greater preference for immediate rewards, indicating greater impulsivity) were associated with lower hoarding symptom severity. The findings suggest that self-reported impulsivity, but not objective performance on a behavioral impulsivity task, may be impaired in HD, and are discussed in terms of cognitive and affective factors in decision-making.