BACKGROUND: Psychosocial maturity is one of the key factors for understanding the course of criminal offences in juveniles and young adults. Until recently, forensic-psychiatric assessments to diagnose a severe disorder of personality development remained mostly unguided because validated instruments were not available. A new tool, the Young Adult Personality Development (YAPD) instrument, was introduced in 2021 and consists of three dimensions related to psychosocial maturity: YAPD environmental, YAPD pathology and YAPD developmental tasks failure. The current study tested the reliability (internal consistency, interrater reliability) and concurrent validity of these dimensions. METHODS: We analysed files of a consecutive sample of young adults in the Canton of Zurich (2007 to 2020, n = 234, mean age: 21.33 years, SD: 1.74 years), who were either assigned to specialised institutional treatment for young adults (Swiss Penal Code SPC Article 61) or outpatient treatment (SPC Article 63). Intraclass correlation coefficient (ICC) agreements were used to analyse interrater reliability of YAPD dimensions across three independent raters. In the absence of a gold standard, we analysed concurrent validity by measuring the associations of the YAPD dimensions with expert opinion and sample status (judicial decisions on measures) using multiple logistic regressions. RESULTS: Expert-rated personality development disorder was found to be highly prevalent in both samples. The YAPD dimensions showed adequate-to-good interrater reliability (ICC: 0.74–0.92). In logistic regression models, YAPD developmental tasks failure was related to diagnoses of severe development disorder and juridical decision on a measure for young adults according to SPC Art. 61. YAPD environmental was related to the diagnosis of a severe development disorder. YAPD pathology was found to be unrelated to the diagnosis of severe personality development disorder. CONCLUSIONS: Our findings support the YAPD developmental tasks failure dimension and to a lesser degree the YAPD environmental dimension as valid dimensions to diagnose severe personality development disorder. Structured assessment instruments such as the YAPD may further improve diagnostic decision-making in forensic psychiatry and psychology.
Aebi et al. (Fri,) studied this question.