The concept of mental disorders is defined as health conditions characterized by various changes in individuals' emotions, thoughts, behaviors, and cognitive processes. The most significant feature of mental disorders is the frequent recurrence and persistence of psychiatric symptoms. Due to their widespread prevalence in society and their substantial contribution to disability, mental disorders are among the groups of diseases requiring early intervention, particularly due to their chronic nature. Chronic mental disorders are associated with hallucinations, delusions, self-stigmatization, and reduced quality of life. Chronic conditions such as schizophrenia, bipolar disorder, and schizoaffective disorder are reported in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to be linked with impairments in occupational and social functionality.

In the literature, these chronic mental disorders are often referred to as "severe," "persistent," or "serious" mental illnesses due to their destructive effects on cognitive, executive, and social skills. Chronic mental disorders, which cause significant disability, are considered a public health issue. Even when the symptoms of diseases such as schizophrenia, bipolar disorder, and schizoaffective disorder are treated, the resulting functional impairments often persist for an extended period, posing a significant burden on both individuals and society. Studies conducted in hospital and community mental health centers have indicated that individuals diagnosed with schizophrenia and bipolar disorder experience impairments in social functioning and significant disabilities.

Research highlights various challenges faced by individuals with chronic mental disorders, such as deterioration in social relationships, stigmatization, lack of motivation, insufficient self-care, and challenges in daily living skills like financial management, communication, and shopping. Another critical issue in individuals with chronic mental disorders is self-stigmatization, which is closely related to social disadvantage and functionality. Studies examining the self-stigmatization levels of these individuals have reported an increase in such behaviors, identifying self-stigma as a significant global concern in the literature.

Consequently, it is evident that psychosocial interventions addressing functionality, insight, and self-stigmatization levels, which are thought to be interrelated, should be prioritized for individuals with chronic mental disorders. Addressing these issues underscores the importance of psychiatric rehabilitation activities designed for this population.

While pharmacotherapy is the first choice in the treatment of chronic mental disorders, research indicates that medications alone do not achieve clinically significant improvements in negative and cognitive symptoms, nor do they produce the desired outcomes in functionality. Current guidelines emphasize that the inclusion of psychosocial interventions alongside pharmacotherapy can yield more favorable outcomes in the prognosis of psychotic disorders. Treatment of chronic mental disorders should not only focus on mitigating psychotic symptoms but also aim to improve quality of life, social, and occupational functioning.

Acceptance and Commitment Therapy (ACT), a relatively new psychotherapy, incorporates psychopathological hypotheses and interventions grounded in contextual behavioral sciences and Relational Frame Theory. Limited studies have shown that ACT applied to patients with psychosis reduces levels of depression and anxiety, enhances psychological resilience, facilitates independent daily living, and thereby improves functionality. In light of these findings, psychosocial interventions for individuals with chronic mental disorders are deemed highly valuable. It is anticipated that ACT applied to these individuals may positively alter the course of the illness, reduce self-stigmatization and internalized shame, contribute to improved functionality, and ultimately enhance quality of life. Conducting research to explore the significance and effectiveness of these interventions is of utmost importance.

Inclusion Criteria:

• Being registered with a Community Mental Health Center (CMHC).
• Providing consent to participate in the study, either personally or through a legal guardian.
• Being between the ages of 18 and 65. Being literate.
• According to the treatment team and records, having been in a stable condition for at least six months.

Exclusion Criteria:

• Being under 18 years of age.
• Presence of an organic psychotic disorder.
• Experiencing an episode during the intervention process.
• Refusing to participate in the study.