Beyond Traits and Categories: The SWAP-200 as a Hybrid Approach to Personality Assessment

Personality is a central determinant of psychological functioning, shaping the onset, course, and treatment outcomes of mental disorders. Reliable personality assessment, however, remains challenging, as traditional methods such as self-report questionnaires and (structured) interviews are vulnerable to bias and limited in capturing dynamic interpersonal processes. The Shedler-Westen Assessment Procedure (SWAP-200) offers an empirically grounded, dimensional, and clinically rich alternative, based on structured clinical observations.This dissertation examines the psychometric properties and clinical utility of the Dutch version of the SWAP-200 in complex mental health populations. Across four empirical studies and a methodological overview, interrater reliability, factor structure, convergent and criterion validity, and differential diagnostic value in individuals with mild intellectual disability (MID-BIF) were investigated. Findings indicate high agreement across raters (ICC = .82), a robust four-factor structure consistent with contemporary dimensional models, and significant overlap between SWAP-200 scales and maladaptive personality traits (PSY-5-r scales). The SWAP-200's clinical utility in complex populations (forensic and MID-BIF) is shown by it's capability to differentiate and measure relevant constructs in populations where reliance on self-report measures is limited and where standard instruments often fall short. Overall, this dissertation demonstrates that the SWAP-200 is a valid, clinically meaningful, and scientifically robust instrument, with particular added value for personality assessment in complex clinical populations.