4 - (SYM 115) Processes of Change in Web-based Acceptance and Commitment Therapy for Hoarding: An Investigation of Mediators and Moderators in a Randomized Waitlist-controlled Trial

Many individuals do not experience clinically significant change even after receiving the gold-standard treatment for hoarding disorder, cognitive-behavioral therapy (CBT). Alternative treatments for hoarding have been evaluated in recent years in hope of identifying both effective treatment options and novel processes of change that can reduce hoarding symptoms. Acceptance and commitment therapy (ACT), which theoretically reduces symptoms and improves well-being by decreasing psychological inflexibility (i.e., the tendency for rigid responses to emotions and thoughts to dominate over one’s behavior) has been investigated in two recent trials and found to be overall efficacious for decreasing hoarding symptoms (Krafft et al., under review; Ong et al., 2021). However, processes of change in ACT for hoarding have not previously been investigated. This presentation will discuss results of a secondary analysis of a randomized waitlist-controlled trial of web-based ACT for hoarding problems.

We examined whether theorized processes of change (psychological inflexibility, mindful awareness, and self-stigma) were related to hoarding symptoms at baseline, and the impact of potential mediators and moderators on ACT for hoarding, in a sample of 73 adults living in the U.S. with clinically significant hoarding symptoms. At baseline, hoarding severity was significantly correlated with hoarding-related psychological inflexibility (r = .52, p < .01), mindful awareness (r = -0.40, p < .01), and self-stigma (i.e., the belief that people who hoard are different from others; r = .31, p < .01). Longitudinal analyses investigating whether hoarding-related psychological inflexibility, mindful awareness, and components of self-stigma at posttreatment mediated hoarding symptoms at follow-up found no significant indirect effects. However, change in hoarding-related psychological inflexibility (r = .73, p < .01) and change in mindful awareness (r = -.69, p < .01) were significantly correlated with change in hoarding symptoms over time. Age, gender, and baseline hoarding-related psychological inflexibility did not significantly moderate the effects of condition. Overall, these findings suggest that hoarding symptoms are related to psychological inflexibility, mindful awareness, and self-stigma; however, it is unclear if these processes mediate the impact ACT for hoarding. Limitations of this study will be discussed, such as the lack of a mid-treatment assessment and use of a symptom cutoff rather than a diagnostic interview.