The onset, prevalence, and developmental course of personality disorders: Towards assessing and fostering personality functioning

Background: Personality disorders (PDs) are among the most severe forms of mental disorders, characterized by an enduring, pervasive, and inflexible pattern of inner experience and behavior that deviates distinctly from general cultural expectations and causes significant distress or impairment. Yet, cumulative findings clearly challenge this notion, suggesting considerable improvement over time. In addition, the conceptualization of PDs is currently in transition, shifting from a categorical to a dimensional approach. As such, research is lagging behind, and clinical translation has yet to take place.
Aims: This thesis adds to the heterogenous body of literature by looking at the prevalence, onset, and course of PDs and PD symptoms over time. Moreover, the current thesis adds to the conceptualization of PDs by examining the extent to which impaired personality functioning mediates the pathogenic effect of childhood maltreatment. In line with the current shift in paradigm, this thesis incorporates both the categorical (Studies 1 and 2) and the dimensional model of PDs (Study 3).
Method: Following a systematic review and meta-analysis of the stability of PDs and PD symptoms over time (Study 1), the current thesis investigates data from a high-risk sample of young adults with a history of child welfare and juvenile-justice placements in Switzerland to examine a) the prevalence, onset and stability of PDs and PD symptoms from adolescence into adulthood (Study 2) and b), to investigate the pathogenic effect of impaired personality functioning between different types of childhood maltreatment and self-reported mental health problems (Study 3).
Results: Findings from Study 1 revealed that PDs, either assessed categorically or in terms of more dimensional symptom counts, decrease significantly over time, thus suggesting a notable trend towards improvement. Nevertheless, between-study heterogeneity is high, and stability itself depends on several methodological factors. Findings from Study 2 indicated that prevalence rates significantly increased from adolescence into adulthood, the onset of PDs occurred in late adolescence, and the stability of PD and PD symptoms was comparable to that in adulthood. Findings from Study 3 finally suggested overall childhood maltreatment and emotional neglect to be particularly relevant in the context of personality functioning, especially in relation to self-functioning. As such, impaired personality functioning, predominantly self-functioning, was found to significantly mediate the pathogenic effect of overall childhood maltreatment and emotional neglect.
Discussion: The stability of PDs and PD symptoms depends on multiple factors which challenge our methodological understanding for capturing stability over time considerably. Future work should, thus, focus on how to redefine ‘stability’ in the context of PDs, and whether the new conceptualization will clarify some of the issues related to the stability of PDs. Nevertheless, it is of the utmost importance to acknowledge that a symptomatic remission is not necessarily accompanied by a full recovery, with most PD patients never managing to fully participate in society despite considerable remission. Specifically targeted intervention methods are, therefore, needed to enable participants to fully engage in society. In addition, more sophisticated analyses, especially person-centered approaches, hold promise for improving our understanding of individual patterns of change and, thus, elucidate the complex nature of mechanisms of change by focusing on protective factors. From a developmental lens, maladaptive PD traits already manifest in early childhood, although the more severe forms of PDs only become clinically apparent in (late) adolescence when adolescents become emotionally, cognitively, and socially able to integrate knowledge about themselves and others into a coherent whole. PDs should, thus, be diagnosed prior to the age of 18 in order to provide the best possible outcomes. The new conceptualization enables clinicians to target unique difficulties by drawing an individualized picture of the patient. This might contribute to developing specifically targeted prevention and treatment methods. Children and adolescents involved in the child welfare and/or juvenile-justice system should, moreover, be systematically assessed for childhood maltreatment, personality functioning, and other mental health problems. Combining interventions designed for personality functioning with trauma-informed practices might counteract the psychopathological outcomes.
Conclusion: The present thesis argues in favor of the new conceptualization by leaving the rather artificial PD categories behind and reintroducing the idea of self and interpersonal functioning as the core feature of PDs. This may enable clinicians to perceive the patient more holistically, with specific traits helping to identify individual problems. This, eventually, may contribute to more personalized and tailor-made treatments. As a matter of fact, we have ignored the individual for far too long and it is time to look at the patient behind the disorder by bringing back into focus the original meaning of personality, namely “the subjective experience of what it means to be human” (Sharp & Wall, 2021, p. 1).