6 - (IOP 38) Personalizing Exposure and Response Prevention for OCD: A Domain-specific Analysis of Treatment Outcomes

Exposure and Response Prevention (EX/RP) is a first-line treatment for Obsessive-Compulsive Disorder (OCD), yet up to one-third of patients do not achieve optimal symptom remission. OCD symptom domains influence treatment outcomes, with contamination and responsibility-for-harm obsessions responding more favorably than unacceptable thoughts and less-studied obsessions, such as those classified as "other." Prior studies examining the relationship between OCD symptom domains and EX/RP outcomes have yielded mixed findings, possibly due to methodological limitations. This study investigates EX/RP outcomes across primary obsession domains, hypothesizing that unacceptable thoughts and "other" obsessions will respond less favorably than contamination, responsibility-for-harm, and symmetry domains.
Data were analyzed from 137 adults with OCD in a randomized controlled trial of EX/RP. Participants received eight weeks of standard EX/RP, with the option for up to eight additional sessions if symptoms remained clinically significant. Independent raters categorized participants’ primary obsession domains into five groups. The primary outcome was post-treatment symptom severity, measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), with statistical analyses examining differences in treatment response and the need for extended EX/RP.
After eight weeks of EX/RP, Y-BOCS scores significantly differed across obsession domains, F(4, 132) = 5.73, p < .001. Patients in the contamination (M = 12.0, SD = 3.1) and responsibility-for-harm (M = 11.8, SD = 3.4) groups had significantly lower post-treatment Y-BOCS scores than those in the unacceptable thoughts (M = 16.2, SD = 4.0, p = .002) and "other" (M = 16.1, SD = 4.2, p = .001) groups. The symmetry group (M = 14.3, SD = 3.7) exhibited intermediate outcomes. The proportion of participants requiring additional treatment sessions also differed by obsession domain, χ2(4, N = 137) = 10.07, p = .039. Patients in the contamination (37%) and responsibility-for-harm (42%) groups were significantly less likely to require additional sessions than those in the unacceptable thoughts (64%) and "other" (70%) groups, while the symmetry group (62%) fell in between.
Findings suggest that contamination and responsibility-for-harm obsessions respond more favorably to EX/RP, while unacceptable thoughts and less-studied obsessions exhibit poorer outcomes. This "other" category included obsessions related to somatic concerns, a need to know or remember, intrusive images, nonsensical sounds or words, distress from noises, and illness-related fears that were not contamination-related. These findings highlight an opportunity to identify domain-specific barriers to EX/RP, including cognitive mechanisms, mental rituals, variability in exposure adherence, and differences in the violation of fear expectations. Future research should refine and personalize EX/RP strategies to improve outcomes for harder-to-treat OCD subtypes, particularly those characterized by unacceptable thoughts and "other" obsession categories.