Nasal spray and kindness training aim to quiet inner critic in BPD

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

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.