(PS9-69) Relationship Between HiTOP Spectra and ACT Processes in Adults with Schizophrenia-Spectrum Disorders

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a novel transdiagnostic framework developed to dimensionalize psychopathology (Kotov et al., 2017). It was proposed to enhance clinical utility over traditional classification methods in treatment formulation and communication with patients (Balling et al., 2023; Ruggero et al., 2019). However, HiTOP’s integration into existing evidence-based treatments, such as Acceptance and Commitment Therapy (ACT), remains largely unexplored. ACT is a process-focused therapy that is empirically supported as a transdiagnostic intervention (Dindo et al., 2017). Thus, ACT may be an ideal treatment for integrating HiTOP into clinical practice. This study examined the relationship between HiTOP spectra (internalizing, detachment, thought disorder, and externalizing) and ACT processes (psychological flexibility [PF], mindfulness [MF], value progress [VP], and value obstruction [VO]) among adults (n = 81) diagnosed with schizophrenia-spectrum disorders (SSD) and recruited during psychiatric hospitalization. Constructs were measured at baseline and 4-month post-discharge follow-up.

Initially, subscales of the Brief Psychiatric Rating Scale (BPRS) and items from the Clinical Outcomes in Routine Evaluation (CORE) were mapped onto each HiTOP spectrum using the current HiTOP model and self-report measure (HiTOP, 2025). The hypothetical framework was further refined through internal consistency (Cronbach's alpha) testing and referencing a previous transdiagnostic factor analysis of the BPRS (Hofmann et al., 2022).

Separate linear regressions were conducted with each ACT process as the predictor and HiTOP spectrum as the outcome at baseline. All ACT processes (PF, MF, VO: p < .001) predicted the internalizing (VP: p </em>= .04) and detachment (VP: p = .03) spectra. When predictors were combined into a multiple linear regression, only PF (p = .002) predicted internalizing, and both VP (p = .01) and VO (p = .003) predicted detachment. Similar regressions were conducted using changes in constructs from baseline to 4 months post-discharge. Changes in PF, MF, and VO (p < .001) predicted changes in internalizing and detachment, and changes in MF and VO predicted changes in thought disorder (MF: p = .02; VO: p = .03) and externalizing (MF: p = .006; VO: p = .005). In a multiple linear regression model, only change in VO predicted changes in detachment (p < .001) and externalizing (p = .03). Significant findings demonstrated consistent directions of association, with PF, MF, and VP showing negative associations with outcomes, while VO was positively associated.

Overall, these findings suggest that ACT processes could predict internalizing and detachment profiles cross-sectionally, and changes in ACT processes—except VP—could predict changes in HiTOP spectra. Notably, VO may be a critical target for interventions that aim to address multiple dimensions of psychological dysfunction in this population. The small sample and lower internal consistencies for some constructs limit the generalizability of these findings. However, exploratory approaches of this nature may promote the integration of emerging transdiagnostic or dimensional models of psychopathology, such as HiTOP, into ACT.