Acceptance and commitment therapy (ACT): the foundation of the therapeutic model and an overview of its contribution to the treatment of patients with chronic physical diseases.

Nowadays, treatment of chronic illnesses, such as stroke, cancer, chronic heart and respiratory diseases, osteoarthritis, diabetes, and so forth, account for the largest part of expenses in western countries national health systems. Moreover, these diseases are by far the leading causes of mortality in the world, representing 60% of all deaths. Any treatment aimed at targeting them might engage an individual for a large portion of his/her life so that personal and environmental factors can play a crucial role in modulating the person's quality of life and functioning, on top of any medical cure. Anxiety, depression, and distress for examples are not rare in patients with chronic diseases. Therefore, Cognitive and Behavior Therapy research has largely contributed in the last decades in identifying and programming interventions on such aspects as real and perceived social and family support, coping abilities, locus of control, self-efficacy that might help patients living with their chronic disease. More recently, third generation Cognitive-Behavior-Therapies, such as Dialectical Behavioral Therapy (DBT), Mindfulness Based Cognitive Therapy (MBCT), Functional Analytic Psychotherapy (FAP) and Acceptance, and Commitment Therapy (ACT) focused their attention and research efforts on developing intervention models targeting the needs of patients with a chronic disease. This paper has three aims. First is to briefly introduce ACT epistemological (Functional Contextualism) and theoretical (Relational Frame Theory) foundations as a stand point for understanding the peculiarity of ACT as a modern form of Clinical Behavior Analysis. The second aim is to introduce ACT clinical model and its six core processes (acceptance, defusion, present moment, self as a context, values and committed action) as both accountable, in their continuum, for psychological flexibility and inflexibility. Third, to present a brief overview of studies and outcomes of ACT intervention protocols and assessment tools that have been investigated in patients with chronic physical diseases, and namely: diabetes, obesity, epilepsy, and chronic pain.