Recent advances in research on personality disorders

Personality disorders are highly prevalent in clinical practice. With the introduction of the Diagnostic Statistical Manual - 5th Edition (DSM-5) the multi-axial system of diagnosis for mental disorders has disappeared, which has led to an increase in research on personality disorders (e.g. Emmelkamp & Meyerbröker, 2020). In this Special Issues, several recent developments are discussed. In the first article (Crisan et al., 2023) in this Special Issue, a meta-analysis is reported investigating the results of studies on the association between adverse childhood events and cluster C personality disorders including avoidant personality disorder, dependent personality disorder and obsessive–compulsive personality disorder. Adverse childhood events included cumulative adverse experiences, childhood maltreatment, dysfunctional parental behaviours, household dysfunction and peer bullying. This meta-analysis found a strong association between childhood adversity and each specific cluster C personality disorder across studies with larger effect sizes in studies that used clinical interviews, compared to studies that used self-report questionnaires. Interestingly, this association decreased with age. Results of a systematic review of Fanti et al. (2023) revealed that paranoia may be transdiagnostic in a variety of personality disorder diagnoses. They found evidence of mild-to-severe paranoia not only in paranoid personality disorder and schizotypal personality disorder but also in borderline personality disorder as well. In addition, they also found evidence of paranoia in a number of patients with antisocial personality disorder, avoidant personality disorder and narcissistic personality disorder. In a study by van der Linde et al. (2023), who investigated complex dissociative disorders, questionnaires measuring personality disorder traits, schema modes and coping styles were completed by patients with avoidant personality disorder, borderline personality disorder and complex dissociative disorder. Results revealed that patients with the complex dissociative disorder—in contrast with patients with avoidant personality disorder and borderline personality disorder—were characterized by specific schizoid, schizotypal, borderline and avoidant personality traits. Interestingly, patients with complex dissociative disorder reported early maladaptive schemas in the domains of disconnection and rejection, and over-vigilance and inhibition. Risky, self-destructive impulsivity and emotion dysregulation are core features of borderline personality disorder (Waite et al., 2024). Two studies in this Special Issue investigated altered emotional patterns in borderline personality disorder. Pyszkowska et al. (2023) studied in patients with borderline personality disorder and in patients with depression whether internalized stigmatization and emotional dysregulation may enhance avoidance strategies, including maladaptive daydreaming. Maladaptive daydreaming was associated with emotional dysregulation and negative attitudes towards oneself. Results revealed further significant differences between borderline personality disorder and depression with higher scores reported by patients with borderline personality disorder in areas of negative affect and emotional dysregulation. Lopez-Villatoro et al. (2023) investigated—using the International Affective Picture System—whether an altered emotional pattern in borderline personality disorder patients was associated with traumatic experiences and attachment bonds towards their primary caregivers. As concluded, the authors' results of this study highlight the relevance of treatment focused on traumatic attachment events for the improvement of emotional instability in patients with borderline personality disorder. The following articles in this Special Issue are focused on evidence-based psychotherapy on patients with personality disorders. In the first study (Nielsen et al., 2023), a scoping review was conducted to identify relevant existing psychotherapy research with patients with schizotypal personality disorder. Unfortunately, very few relevant studies have been conducted with this group of patients and results are inconclusive. Schema therapy is one of the evidence-based psychotherapies for personality disorders (Emmelkamp & Meyerbröker, 2020), but most studies have involved individual schema therapy. Wibbelink et al. (2023) investigated in a large multicentre open trial the effectiveness of group schema therapy for cluster C personality disorders. Results revealed that 30 sessions of group schema therapy resulted in significant improvements with medium to large effect sizes after 2 years for avoidant and dependent personality disorder, but results for obsessive–compulsive personality disorder are inconclusive. In the study of Khasho et al. (2023), the effectiveness of schema therapy was investigated in older adults with borderline personality disorder using a multiple baseline case series design. Results revealed that schema therapy led to a significant decrease in negative core beliefs. In addition, patients no longer fulfilled the criteria of borderline personality disorder. Few studies have investigated the treatment of borderline problems in adolescents (e.g. Schuppert et al., 2012). In the next article in this Special Issue (Gilbey et al., 2023), 6 months of mentalization-based therapy is investigated in a therapeutic community setting with adolescents with borderline personality problems. Results indicate that participants show a reduction in self-harm and internalizing symptoms. High rates of dropout have been widely reported in evidence-based psychotherapies for patients with borderline personality disorder. In the following study published in this Special Issue, De Freixo Ferreira et al. (2023) investigated drop-out in published randomized controlled trials in which patients with borderline personality disorder were treated with evidence-based psychotherapy. Results revealed that patients with weaker therapeutic alliance scores and higher hostility presented with higher dropout rates. Last but not least, comorbid personality disorder has been studied as a predictor for treatment efficacy and dropout in treatments, especially with patients treated for post-traumatic stress disorder (e.g. Snoek et al., 2021). In the last study in this Special Issue, van den End et al. (2023) investigated whether co-morbid personality disorder had negative effects on treatment outcomes for post-traumatic stress disorder. Interestingly, the results were negative: personality disorder did not predict change in post-traumatic stress disorder.