Oxytocin Plus Self-compassion Training in Borderline Personality Disorder

Inclusion Criteria: * Diagnosis of Borderline Personality Disorder (BPD) according to two semi-structured interviews: the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II) and the Revised Diagnostic Interview for Borderlines (DIB-R). * Aged between 18 and 50 years, inclusive. * Pharmacological treatment stability maintained throughout the intervention period. * Previous treatment for BPD, specifically Standard Dialectical Behavior Therapy (DBT) or DBT Skills Training. * High levels of self-criticism, defined as scores \> 12 on the Inadequate Self (IS) subscale of the Forms of Self-Criticizing/Attacking \& Self-Reassuring Scale - Short Form (FSCRS-SF). Exclusion Criteria: * Presence of comorbid psychiatric disorders, including: Schizophrenia, Psychotic Disorders, Bipolar Disorder, Current Major Depressive Disorder (MDD), Substance Dependence, Organic Brain Disease, or Intellectual Disability, as determined by medical examination and clinical assessment using the SCID-I (Structured Clinical Interview for DSM-IV Axis I Disorders). * History of severe endocrine disorders. * History of medical conditions, specifically: Epilepsy, Renal Insufficiency (Kidney Failure), or Heart Failure. * Concurrent participation in any other psychotherapy or psychological treatment during the study period. * Women of childbearing potential who are unwilling or unable to use highly effective contraception (e.g., oral contraceptives, intrauterine device \[IUD\], partner's vasectomy, tubal ligation, or sexual abstinence) throughout the entire duration of the study. * Intention to become pregnant or planning a pregnancy during the course of the study. * Current pregnancy or breastfeeding at the time of enrollment or during the study. * Concomitant medical treatment that is incompatible with the administration of intranasal oxytocin.