Mechanisms of Change in Day Treatment Group Schema Therapy for Severe Personality Disorders: A Multiple Baseline Single‐Case Study

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Main Authors: Joska van Houten, Samantha Bouwmeester, Nathan Bachrach
Format: Artículo Open Access
Published: Wiley 2026
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author Joska van Houten
Samantha Bouwmeester
Nathan Bachrach
author_facet Joska van Houten
Samantha Bouwmeester
Nathan Bachrach
Joska van Houten
Samantha Bouwmeester
Nathan Bachrach
collection Wiley Open Access
contents Mechanisms of Change in Day Treatment Group Schema Therapy for Severe Personality Disorders: A Multiple Baseline Single‐Case Study Joska van Houten Samantha Bouwmeester Nathan Bachrach Clinical Psychology & Psychotherapy ABSTRACT Although schema therapy (ST) is an effective intervention for individuals with personality disorders (PDs), its mechanisms of change are not yet well delineated. Understanding these mechanisms is essential for determining the key processes that optimize treatment efficacy. This study investigated mechanisms of change in day treatment group ST (DT‐GST) for patients with severe PDs. PD severity was the primary outcome in a multiple‐baseline single‐case design, assessed before and after DT‐GST, alongside idiosyncratic negative core beliefs measured weekly over 30 weeks. Secondary outcomes were early maladaptive schemas (EMS) and schema modes (SMs), measured pre‐ and post‐treatment. Mechanisms of change were examined through visual inspection, correlations and randomization tests. Changes in PD severity moderately correlated with changes in negative core beliefs ( r  = 0.57), but not with SMs. Negative core beliefs correlated positively with the Vulnerable Child ( r  = 0.76), Punitive Parent ( r  = 0.78), Demanding Parent ( r  = 0.61) and Detached Self‐Soother ( r  = 0.58) modes and negatively with the Happy Child ( r  = −0.77) and Healthy Adult ( r  = −0.57) modes. Meaningful change occurred across all treatment phases, with the greatest therapeutic progress in the second and third phases. This study highlights the central role of idiosyncratic negative core beliefs in reducing PD severity while also underscoring the importance of changes in SMs. Findings suggest that ST should prioritize reducing the Vulnerable Child mode and its associated EMS while reinforcing adaptive Healthy Adult and Happy Child modes and diminishing maladaptive Parent and detachment‐related coping modes. Further longitudinal research with repeated assessments is needed to clarify mechanisms of change in ST. 10.1002/cpp.70289 http://creativecommons.org/licenses/by-nc-nd/4.0/
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spellingShingle Mechanisms of Change in Day Treatment Group Schema Therapy for Severe Personality Disorders: A Multiple Baseline Single‐Case Study
Joska van Houten
Samantha Bouwmeester
Nathan Bachrach
Clinical Psychology & Psychotherapy
Mechanisms of Change in Day Treatment Group Schema Therapy for Severe Personality Disorders: A Multiple Baseline Single‐Case Study Joska van Houten Samantha Bouwmeester Nathan Bachrach Clinical Psychology & Psychotherapy ABSTRACT Although schema therapy (ST) is an effective intervention for individuals with personality disorders (PDs), its mechanisms of change are not yet well delineated. Understanding these mechanisms is essential for determining the key processes that optimize treatment efficacy. This study investigated mechanisms of change in day treatment group ST (DT‐GST) for patients with severe PDs. PD severity was the primary outcome in a multiple‐baseline single‐case design, assessed before and after DT‐GST, alongside idiosyncratic negative core beliefs measured weekly over 30 weeks. Secondary outcomes were early maladaptive schemas (EMS) and schema modes (SMs), measured pre‐ and post‐treatment. Mechanisms of change were examined through visual inspection, correlations and randomization tests. Changes in PD severity moderately correlated with changes in negative core beliefs ( r  = 0.57), but not with SMs. Negative core beliefs correlated positively with the Vulnerable Child ( r  = 0.76), Punitive Parent ( r  = 0.78), Demanding Parent ( r  = 0.61) and Detached Self‐Soother ( r  = 0.58) modes and negatively with the Happy Child ( r  = −0.77) and Healthy Adult ( r  = −0.57) modes. Meaningful change occurred across all treatment phases, with the greatest therapeutic progress in the second and third phases. This study highlights the central role of idiosyncratic negative core beliefs in reducing PD severity while also underscoring the importance of changes in SMs. Findings suggest that ST should prioritize reducing the Vulnerable Child mode and its associated EMS while reinforcing adaptive Healthy Adult and Happy Child modes and diminishing maladaptive Parent and detachment‐related coping modes. Further longitudinal research with repeated assessments is needed to clarify mechanisms of change in ST. 10.1002/cpp.70289 http://creativecommons.org/licenses/by-nc-nd/4.0/
title Mechanisms of Change in Day Treatment Group Schema Therapy for Severe Personality Disorders: A Multiple Baseline Single‐Case Study
topic Clinical Psychology & Psychotherapy
url https://onlinelibrary.wiley.com/doi/10.1002/cpp.70289