Introduction: Borderline personality disorder (BPD) is a severe condition related to emotion, self-image and relationships instability, feelings of abandonment and emptiness, marked impulsivity, self-harm behaviors and suicide ideation. Patients with BPD often show decreased quality of life and well-being, and present one of the highest suicide rates of mental disorders. This disorder has a developmental path that often begins in childhood and the onset usually occurs in late adolescence or early adulthood. Identifying marked borderline features at early ages would be valuable to refer adolescents for appropriate treatment and prevent these features’ growth. Moreover, research on psychological processes in adolescence is scarce but crucial to understand the development of BPD and sustain and design psychotherapeutic interventions. Thus, this doctoral dissertation aimed (1) to provide valid and adapted instruments for early assessment of borderline symptoms in the Portuguese population, (2) to describe and characterize youth borderline features in Portugal, identify internal risk and protective factors and examine the relationships between them and finally, (3) to longitudinally explore different trajectories of borderline features and test the influence of self-disgust and self-compassion over time.
Methods: This research included ten studies, of which four are psychometric, four cross-sectional and two longitudinal. Most studies were conducted with convenience adolescent samples from the general population. In one study was used a sample of parents, in two studies were used panels of experts in mental health, and in another was used a sample of adolescents with non-suicidal self- injury (NSSI) history. Data were collected in schools and online, mostly through self-report questionnaires. Additionally, data from parent-rated questionnaires and a clinical interview was also collected. Statistical analyses were conducted using the SPSS (and PROCESS Macro), AMOS and MPLUS.
Results: The psychometric studies indicated that (I) the Borderline Personality Features Scale for Children (BPFS-C) and for Parents (BPFS-P) are valid, reliable and brief questionnaires to assess borderline features in youth; (II) the Multidimensional Self-Disgust Scale for Adolescents (MSDS-A) showed good psychometric quality, with good convergent validity and also temporal stability; (III) the Clinical Interview for Borderline Personality Disorder for Adolescents (CI-BOR- A) was accepted by youth and the expert panel classified the instrument as generally good, providing important suggestions and comments to improve its quality; (IV) and the English version of the CI-BOR-A was approved by English experts and is now also available to be used in other countries. In turn, cross- sectional studies showed that (V) the more prevalent borderline features amongst Portuguese youth were feelings of abandonment, emotional intensity, and an unstable self-image; and that impulse, suicide ideation, stress and depression were significant predictors of borderline features; (VI) girls exhibited higher borderline features and self-disgust than boys, and lower self-compassion; (VII) mindfulness, isolation, and self-judgement were the self-compassion factors that mediated the relationship between memories of subordination and threat in childhood and borderline features; (VIII) self-compassion stood in the way of self-disgust and borderline features, highlighting the mediating role of self-compassion. Longitudinal studies revealed that (IX) self-compassion protected adolescents with NSSI from developing borderline features over six months; and (X) adolescents who already had higher borderline features seem to present a gradually rising trajectory, and feelings of self-disgust increased borderline features over one year.
Conclusions: Early assessment of borderline features, BPD and related constructs is essential to identify adolescents that need appropriate treatment. The BPFS-C, BPFS-P, MSDS-A, and the CI-BOR-A can now be used for this purpose in the Portuguese population. Self-disgust increases the risk of adolescents growing borderline symptoms and self-compassion might counter this effect and evolution. Targeting self-disgust and cultivating self-compassion in adolescents with subthreshold BPD symptoms could mitigate the development of borderline features, decreasing BPD occurrence in adulthood, with significant implications for patients, families, communities, and society.
Keywords: borderline features, adolescence, self-compassion, self-disgust, non-suicidal self-injury, developmental trajectories, assessment, prevention