Therapists
SPD
Therapists were included as participants in this study. Inclusion criteria for all the therapists were the following: (a) being 18 years or older, (b) being a clinical psychologists who had completed a 4-year formal psychotherapy training, (c) having at least 5 years of experience in treating PDs. More specifically, study therapists must have had at least 5 years of experience in either CBT or metacognitively oriented therapy plus CFT for control or experimental group, respectively. Therapists also had to have the (d) availability to provide psychotherapy to clients diagnosed with SPD, and (e) availability to engage in 90-min of supervision every two weeks. Considering the limited sample size of the RCT and the novelty of the experimental treatment, we opted for minimizing the variance of therapists skills and competences and maximizing the adherence to an ideal curriculum of a training program that has not been implemented yet. Therefore, we found just two therapists who could provide SPD-tailored psychotherapy, one for each arm of the study.