Efficacy of "DBT-LIVE", an Identity Skills Training Program, for Borderline Personality Disorder.

• DBT LIVE (Behavioral): Identity disturbance skills based on DBT
• TAU (Behavioral): Treatment as usual

Primary outcomes

• Self-concept and Identity Measure (SCIM) (Kaufman et al., 2015) [baseline; immediately after the intervention; 6 months]: It is a 27-item self-report instrument designed to evaluate identity consolidation and clinically significant identity disturbance. The SCIM items were created to assess key components of identity, as well as the presence or absence of disturbances in these areas. These components include: a) the continuity of self-concept and roles across different settings and interpersonal contexts, b) the consistency of personal values and interests, c) self-esteem, d) differentiation between oneself and others, and e) self-cohesion, understood as the feeling of being whole or complete. Participants were asked to rate the extent to which they agreed or disagreed with 27 statements. Responses were provided on a 7-point scale ranging from 1 to 7 (1 = strongly disagree, 2 = disagree, 3 = somewhat disagree, 4 = neither agree nor disagree, 5 = somewhat agree, 6 = agree, and 7 = strongly agree). Subscale scores were computed according to the direction of the construct being measured.
• Difficulties in Emotion Regulation Scale (Gratz & Roemer, 2004); Spanish validation of Hervás & Jódar (2008). [baseline; immediately after the intervention; 6 months]: It adapted into Spanish by Hervás \& Jódar (2008), comprises 28 items that assess difficulties in several domains of emotion regulation, including emotional non-acceptance, emotional neglect, everyday interference, emotional confusion, and emotional dyscontrol. Responses are given on a 5-point Likert scale (1 = almost never; 5 = almost always), with higher scores indicating greater difficulties in emotion regulation. The Spanish version demonstrated high internal consistency .93 and acceptable psychometric properties, as well as convergent and incremental validity in both cross-sectional (N = 254) and longitudinal (N = 60) samples. This makes it a suitable and validated instrument for assessing difficulties in emotion regulation in Spanish-speaking adult populations.

Secondary outcomes

• Self-compassion Scale (SCS) (Neff, 2003); Spanish validation of García-Campayo et al. (2014). [baseline; immediately after the intervention; 6 months]: Adapted into Spanish by García-Campayo et al. (2014), comprises 26 items (long form) designed to assess self-compassion across six components: self-kindness, self-judgment, common humanity, isolation, mindfulness, and over-identification. Items are rated on a 5-point Likert scale (1 = almost never; 5 = almost always), with higher values indicating greater self-compassion. The Spanish version demonstrated good internal consistency .87 and adequate psychometric properties, including test-retest reliability and construct validity, supporting its use in Spanish-speaking populations. The authors also validated a short form (12 items, SCS-SF), which showed .85 for the total score and acceptable subscale reliability, as well as stability over time and strong correlation with the full version.
• Meaning in Life Questionnaire (MLQ) (Steger et al., 2006); Spanish validation of Marco et al. (2022). [baseline; immediately after the intervention; 6 months]: In its Spanish version by Marco et al. (2022), measures two core dimensions of meaning in life: presence of meaning and search for meaning. The MLQ is composed of 10 items (five per dimension), rated on a 7-point Likert scale (1 = false; 7 = true), with higher scores indicating greater presence or search of meaning. In the Spanish adaptation, two-factor structure (Presence / Search) was confirmed via confirmatory factor analysis, with good internal consistency (Presence .86; Search .87). Test-retest reliability (one-month interval) was moderate (≈ .70 for Presence; ≈ .73 for Search), and the Spanish MLQ showed adequate convergent validity with measures of purpose, well-being, anxiety, and depression. Therefore, the Spanish MLQ is a valid and reliable instrument for assessing meaning in life in adult Spanish samples.
• Suicide Behaviors Questionnaire-Revised (SBQ-R) (Linehan, 1981); Spanish validation of García-Nieto et al. (2013). [baseline; immediately after the intervention; 6 months]: It's a brief self-report instrument consisting of 4 items, designed to assess past and current suicidal thoughts and behaviors, as well as the likelihood of future suicide. In the Spanish adaptation, administered to a sample of 325 undergraduates, the SBQ-R showed good internal consistency .81 and temporal stability (test-retest ICC = .88). A confirmatory factor analysis supported the construct's validity of the scale, and criterion-related validity was demonstrated via correlations with other psychological measures. Thus, the Spanish SBQ-R appears to be a reliable and valid tool for identifying individuals - especially among young adults - at elevated risk of suicidal behavior.
• Level of Personal Functioning Scale (LPFS) (Bender et al., 2011); Spanish validation of Schetsche, (2021). [baseline; immediately after the intervention; 6 months]: It was translated and adapted into Spanish by Schetsche (2021). The Spanish LPFS-BF 2.0 retains the conceptual structure of the original, assessing personality functioning along two correlated domains: self-functioning and interpersonal functioning, and allowing for a general functioning score. In the adaptation study (N = 361), confirmatory factor analysis supported a bifactorial structure (self-vs. interpersonal functioning plus a general factor), internal consistency was found to be acceptable, and convergent validity was demonstrated through significant correlations with personality trait measures. Therefore, the Spanish LPFS-BF 2.0 constitutes a valid and reliable instrument for assessing personality functioning in Spanish-speaking populations.
• Acceptability of Intervention Measure (AIM), Intervention Appropriateness Measure (IAM), and Feasibility of Intervention Measure (FIM) (Weiner et al., 2017). [baseline; immediately after the intervention; 6 months]: It's a brief (4-item) self-report instrument designed to assess key implementation outcomes: perceived acceptability, appropriateness, and feasibility of an intervention or implementation strategy. Each item is rated on a 5-point Likert scale ranging from 1 = "completely disagree" to 5 = "completely agree," and higher scores indicate greater perceived acceptability, appropriateness, or feasibility. Psychometric evaluation demonstrated good internal consistency (α between .85 and .91 in the 4-item forms), structural validity (three-factor confirmatory factor analysis with acceptable fit: CFI ≈ 0.96, RMSEA ≈ 0.08), test-retest reliability (coefficients between .73 and .88 after \~7 weeks), known-groups validity, and sensitivity to change across time. Given their brevity, general wording (not tied to specific contexts), and robust psychometric properties, these measures are suitable for use across diverse settings, stakeholder groups, and intervention types.

Sex: All, ages: 16 Years to any

Inclusion Criteria:

* Being 16 years old or more.
* Having the diagnosis of Borderline Personality Disorder.
* Currently receiving treatment or follow-up care at the recruitment center mentioned above.
* Signing the informed consent form to participate in the study; in the case of minors, consent must be provided by parents or legal guardians.

Exclusion Criteria:

* Individuals with severe conditions that may interfere with participation in the research-such as psychosis, schizophrenia, or intellectual disability.
* Individuals with high substance use who are not in optimal condition to follow the treatment program.
* Individuals who present an imminent risk of suicide or who are not in adequate psychological condition to participate in the program.