Study design was a multicenter, randomized, rater-blind clinical trial. There were two-parallel arms (1:1) to evaluate functional, clinical and cognitive efficacy of a specific cognitive rehabilitation group intervention (CR) compared with a psychoeducational group intervention (PE) in subjects with Borderline Personality Disorder (BPD).

To ensure the reliability among centers regarding the evaluation and the treatment fidelity, two meetings were organized before the start of the study to train therapists in the evaluations and interventions.

Clinical and neuropsychological evaluations before interventions were administered in different days since they lasted in general more than one hour each one and the effect of fatigue or boredom might affect the results. Clinical interviews were performed by experienced psychiatrists and psychologists during 3 months to ensure the follow-up of all participants prospectively. The following sociodemographic and clinical variables were collected: age at recruitment, gender, education level, occupational status, and pharmacological treatment. All participants were then randomized to receive CR or PE in a 1:1 ratio stratified by center, age, and education level. Randomization was accomplished with the use of computer-generated sequence.

During the study, subjects did not receive any other individual or group psychotherapy. All patients continued pharmacological treatment if it had been initiated prior to inclusion. Type and doses of medication could not be modified during the study period. Both interventions were applied in a group format and were conducted by two psychologists with experience in managing patients with BPD. Subjects were instructed not to disclose any information about the intervention to maintain blind conditions. Participants were evaluated at baseline, after completion of the intervention, and six months after the end of the interventions.

The study was conducted in accordance with the ethical principles of the Declaration of Helsinki and the approval of the Ethical Committee for this study was obtained. All subjects received extensive information about the study and provided written informed consent before they were enrolled in the study.

Inclusion Criteria:

• Outpatients aged 18 to 45 years;
• Diagnoses of BPD according to Diagnostic and Statistical Manual for Mental Disorders (4th version Revised) (DSM-IV-TR) criteria and evaluated by two semi-structured diagnostic interviews
• Structured Clinical Interview for DSM-IV Axis II Disorders (SCID-II) and the Revised Diagnostic Interview for Borderlines (DIB-R)
• Clinical severity measured with Clinical Global Impression for BPD (CGI-BPD) higher than 4;
• Functional impairment measured with a Global Assessment Functioning (GAF) lower than 65.

Exclusion Criteria:

• No severe physical conditions, such as organic brain syndrome or neurological disease that could affect neuropsychological performance;
• Intelligence Quotient (IQ) < 85;
• Major Depression Disorder (MDD) or substance misuse within the last 6 months;
• Schizophrenia, severe psychotic disorder or bipolar disorder;
• Previous participation in any psychoeducation or cognitive rehabilitation intervention.