Conduct a pilot, single-center, randomized controlled 2-arm study aimed to evaluate the impact of an in-depth 3rd wave CBT program targeting correct self-identification (3rd level of 3rd wave CBT), compared to a control group receiving an acceptance and commitment therapy (ACT; (1st level of 3rd wave CBT, a well-known psychotherapy). Main judgment criteria : Therapeutic response (reduction ≥ 50% between pre and immediate post-treatment), and rate of relapse at 6 months post-therapy. Secondary objectives: Evaluate psychological processes involved in the reduction of moral pain, diligence, ruminations, suicidal ideas, self-concept and alterations in functioning (mental and social), psychological skills.

According to the World Health Organization (WHO), depression is one of the health problems most prevalent mental health issues of the 21st century. Currently available treatments are insufficient to treat effectively combat depression, prevent relapse, and provide a care offer accessible to all people. requiring. Self-identification is at the heart of the dimensional understanding of this disorder, including moral pain inherent is associated with excess suicide mortality. From altered relationships to negative affectivity and affectivity positive are central psychological processes that maintain depression and promote relapse. Cognitive and behavioral psychotherapies (CBT) are the reference in addition to medications. The paramedical team (nurses and psychologists) of the Therapies Center (CHU Montpellier) has created a program targeting correct Self-Identification (SIP; 3rd level of 3rd wave CBT), allowing the reestablishment of functional relationships. This notable innovation was welcomed by the World Health Organisation, which requested its presentation during the meeting of the United Nations in Geneva in June 2021 (international exhibition on resilience).

Main objectives: Conduct a pilot, single-center, randomized controlled 2-arm study aimed to evaluate the impact of an in-depth 3rd wave CBT program targeting correct self-identification (3rd level of 3rd wave CBT), compared to a control group receiving an acceptance and commitment therapy (ACT; (1st level of 3rd wave CBT, a well-known psychotherapy). Main judgment criteria : Therapeutic response (reduction ≥ 50% between pre and immediate post-treatment), and rate of relapse at 6 months post-therapy. Secondary objectives: Evaluate psychological processes involved in the reduction of moral pain, diligence, ruminations, suicidal ideas, self-concept and alterations in functioning (mental and social), psychological skills.

Statistical analysis: A descriptive analysis of the initial characteristics of the patients will be carried out in each of the groups to check initial comparability. The analyzes of the judgment criteria will be carried out with an intention-to-treat analysis.

Feasibility: Paramedical team (nurses and psychologists) specialized in 3rd wave CBT (200 patients/week), coordinated by Dr Ducasse (internationally recognized in the field).

Outcomes/prospects: This program should 1) reduce the frequency and intensity of mental illnesses symptoms, and the associated mental pain, 2) prevent the negative consequences of mental illnesses (poor quality of life, isolation, self-damaging behavior), 3) reduce the mental illness stigma.

3rd wave CBTs constitute programs that can be delivered in group sessions by both nurses and psychologists, with appropriate training. This ensures its potential for wide distribution, where France faces a shortage of psychotherapeutic offerings.

Such a program will undeniably constitute an important contribution on the dimensional understanding of mental illnesses, and the implementation of innovative transnosographic psychotherapeutic care.

Inclusion Criteria:

• Patients aged 18 to 70 years, presenting a current major depressive episode (according to DSM 571), as part of unipolar or bipolar depressive disorder

Exclusion Criteria:

• Patients with a psychotic disorder
• Patients with active thoughts of suicide with intention to carry out the act (C-SSRS "ideation suicidal" in the last week ≥ 4)
• Inability to receive informed information about the study
• Exclusion period determined by a previous study
• Adult protected by law or patient under guardianship or curatorship
• Not be affiliated to a French social security scheme or beneficiary of such a scheme
• Not being able to give informed written consent
• Pregnant or breastfeeding women
• Patients under judicial protection