Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Robbert Langwerden (Donders series 594)

15 February 2023

Promotors: prof. dr. Jos I.M. Egger , prof dr. Paul T. van der Heijden
Copromotor:prof. dr. Jan J.L. Derksen

The normalcy of individual differences: Investigating dimensional and hierarchical psychopathology using the MMPI-2-RF

Psychopathology is a complex and multifaceted concept. Dimensional approaches to psychopathology, such as the Hierarchical Taxonomy of Psychopathology (HiTOP), can be the foundation of a more inclusive, person-centered, reliable, valid, and comprehensive assessment. By relying on dimensional approaches, a more complex and nuanced impression can be realized, emphasizing individual differences and the normalcy of this variance. The studies in my dissertation focused on multiple facets of dimensional operationalization of psychopathology, assessed using the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF). The results demonstrated that (1) the maladaptive personality traits measured by the PSY-5-r showed moderate to strong rank-order stability over 20 years in adults, (2) all five personality psychopathology traits measured by the PSY-5-r show content unipolarity, indicating the PSY-5-r scales measure the outer psychometric ends of maladaptive personality trait spectra, such that symptomatology and functional impairment are linearly associated with the trait level, (3) the HiTOP dimensional and hierarchical structure can be replicated when using a purely data-driven, bottom-up, Bayesian approach, indicating structural validity of dimensional hierarchical models, (4) the autism spectrum disorder and cluster C personality trait symptom and trait profiles were comparable, suggesting that the MMPI-2-RF and dimensional approach might not be sufficient to assess each of these categorical phenotypes in clinical practice and research as well as the significant symptom-overlap between these two DSM-type categories. Finally, (5) a broader context framework was developed to place multidimensional traits and symptoms in context of identity, environment, culture, and other factors that are important for health. Multidimensional measurement of many of these factors could allow for inclusive and comprehensive research and clinical interventions. The findings from these studies taken together provide further support for dimensional assessments of individual differences in symptoms and traits by demonstrating the versatility, reliability, and validity of dimensional constructs. In this research, I applied a variety of methodologies and statistical methods to distill clinical results. Further, this dissertation makes the case for a person- in-the-environment approach, urging for psychology researchers to incorporate environmental factors that are determinants of mental health. These factors include but are not limited to environmental factors (e.g., zip code, proximity to (quality) education and (quality) health care), social factors (e.g., racism, discrimination, microaggressions, intersectional identities), as well as strengths (e.g., cultural, and individual, such as community connectedness and resilience).