70 couples (married or cohabiting) will be recruited across 5 countries (12-18 in each country: Argentina, Costa Rica, Guatemala, México, and Spain). After their entry into the study is confirmed, couples will be randomly allocated into one of two groups: intervention or control (no intervention). In each country, both groups will have equal number of couples.

Couples in the intervention group will receive 20 sessions of Emotionally Focused couple Therapy (EFT). Couples in the control group will receive no intervention during the study period (they will receive a shorter intervention after the trial is over). Participants of both groups will fill questionnaires before allocation, during the intervention period and after the intervention period.

The main outcomes will be couple attachment, couple satisfaction and dyadic adjustment.

The original timeline for the study was to start in Argentina and Guatemala in February 2020, and the remaining countries in September 2020. The study started in February 2020 for Argentina and Guatemala, but in April 2020 the process was postponed due to mobility constrains during covid-19 crisis. During these two months, the process remained in the recruitment phase. Therefore, couples were not randomly assigned. Due to an improvement in the pandemic situation, the study started in Spain in September 2021.We expect the remaining countries will start during 2022.

The study period for each couple will be around 6 months.

A detailed description about the procedure of this clinical trial will be available on an open access study protocol document or paper upon request.

Some more details about therapists, supervision during treatment phase, implementation checking and research team, is offered below.

Participating therapists were chosen based on a rigorous criterion focused on excellence in the adherence to the EFT model. There therapists also had to meet the following prerequisites: (1) Meet all legal requirements necessary to practice therapy in the country and region in which the therapist is located (licensure, insurance, etc.); (2) Have a video recording device; (3) Have completed the Externship, Core Skills and at least 10 hours of EFT supervision by the 1st of June, 2019; (4) Have experience applying the EFT model in couples therapy; and (5) be a licensed therapist or actively participating in case supervision. Additionally, candidates for participating therapists must send a video of at least 20 minutes of a session of actual couples therapy recorded in the last three months, to the principal investigator (MR-G) with their application. The couple in the recording was asked for their consent to have this video be reviewed by two supervisors who are participating in the study. Each video was shared through a secure channel with Martiño Rodríguez, who then sent said video to two EFT certified therapists and/or supervisors from a list of six therapists provided by Samuel Jinich, PhD and Certified EFT Trainer. Each evaluator submitted their evaluation independently to the principle investigator. In the event that a discrepancy arose, a third evaluation was sought from a separate evaluator. In some cases, a second video was requested to resolve doubts regarding a candidate's suitability. A total of 26 therapists sent in an application to participate, of those 11 applications were considered insufficient, and 15 met the requirements of the evaluation. This application and evaluation process took place between January and September, 2019.

All sessions will be videotaped and/or audio-taped for supervision and research purposes.

Supervision of the therapy process will be offered biweekly, in an individual meeting (one therapist, one supervisor) of one hour. Participating supervisors are required to speak Spanish and to certified as a supervisor by the International Center for Excellence in Emotionally Focused Therapy; Ottawa, Canada (ICEEFT), or to be certified by ICEEFT as a therapist and actively be in the process of becoming an ICEEFT certified supervisor.

In order to ensure the therapists in this study are implementing EFT faithfully, two different procedures will be carried out. First, during the supervision meetings with participating therapists, the supervisor will review video recording segments of therapy to determine if EFT is being conducted with adherence to the model. Second, once the study ends, two independent raters will be asked to rate at least 5 sessions of each therapist's taped sessions to ensure that at least 80% of the therapists' interventions can be coded as adherent to the model.

The research team, with their relevant experience, includes the following individuals: Martiño Rodriguez-Gonzalez, Ph.D. (Principal Investigator, Certified Couple Therapist in Spain and Researcher at the Institute for Culture and Society (ICS), Universidad de Navarra, Spain), Shayne Anderson, Ph.D., (Co-Principal investigator; Associate Professor at the Brigham Young University (BYU), USA, and Psychotherapist at the BYU Comprehensive Clinic, USA), Marie-France Lafontaine, Ph.D., (Director of the Couple Research Laboratory, Full Professor at the University of Ottawa and a certified psychologist in Ontario and Quebec, Canada), Paul Greenman, Ph.D. (Full Professor and Chair of the Department of Psychoeducation and Psychology at the Université du Québec en Outaouais, and a certified psychologist in Ontario and Québec, Canada), Alfonso Osorio, Ph.D. (Associate Professor at the School of Education and Psychology and researcher at the Institute for Culture and Society, ICS, Universidad de Navarra, Spain), Jonathan Sandberg, Ph.D. (Full Professor School of Family Life at the Brigham Young University, USA), Jokin de Irala, PhD. (Associate Professor at the School of Medicine and Principal Investigator of the Research group "Educación de la afectividad y de la sexualidad humana" (EASH) at the Institute for Culture and Society, ICS, Universidad de Navarra, Spain), Patrick Steffen, Ph.D. (Full Professor in the Psychology Department at the Brigham Young University, USA), María Calatrava, Ph.D. (Researcher at the Institute for Culture and Society, ICS, Universidad de Navarra, Spain), Maria del Pilar Martínez, PhD. (Full Professor at the School of Social sciences, Department of Psychology, Universidad Pontificia Comillas, Madrid, Spain).

Inclusion Criteria:

• Each couple has to be exclusive in their courtship and been living together for at least 1 year. Participants must be willing to participate in all of the study components (questionnaires, videotaping, therapy, and follow-up once therapy is finished). Each member of the relationship must speak Spanish as a native language and have lived in the country where the study is going to be conducted (Argentina, Costa Rica, Guatemala, Mexico, Spain) for at least 5 years. Couple's average score on the Dyadic Adjustment Scale (DAS; Spanier, 1976) must classify the relationship as mildly to moderately distressed (80-100).

Exclusion Criteria:

• Either partner of the couple is receiving current psychotherapeutic (psychological or psychiatric) treatment or anticipates receiving this type of treatment (not directly involved with this study) within the next 6 months.
• Either member has been previously diagnosed with any psychotic, somatoform or dissociative disorder.
• Either partner is currently taking any medication known to treat psychosis, somatoform, dissociative or psychotic disorders or is taking any psychotropic medication, has a diagnosis of a neurodevelopmental (e. g., autism spectrum disorder), neurocognitive, personality or paraphilic disorder.
• Either partner reports having been arrested or in prison in the past 3 months due to driving drunk or any other legal problem related to alcohol or other drugs, reports having been fired from her/his job due to alcohol or substance use/abuse, reports an episode (as a victim and/or perpetrator) of a sexual assault during the past 2 years, reports current physical or sexual violence in their relationship, or is currently involved in an affair which he/she will not end or requests that the affair remains secret.
• Either partner has a condition or anticipates having a condition that may make attending therapy sessions unlikely (e.g., major surgery expected in the next 3 months, or moving to a new area in the near future, etc.), is misusing/abusing drugs or alcohol, is a psychotherapist active in clinical practice and/or has a direct knowledge of the model because he/she is in training or trained in EFT.