The problem of quality of life in chronic somatic diseases is becoming increasingly important. To solve this, there is a need for the fundamentally new approach to understanding a relationship between somatic and mental disorders, which follows from the concept of multimorbidity. This approach is based upon the unity of the pathological process manifested in nosogenetically diverse, but pathogenetically complementary disorders. According to this position, psychopathological conditions are considered not so much to be random and independent comorbidities as manifestations of abnormal behavior caused by changes in the functional systems involved in the synchronized pathological processes. This statement calls for a radical revision of a set of professional competencies that are of paramount importance for practitioners. In particular, there is an urgent need to raise the attention and qualification of general practitioners in the treatment of mental disorders in patients with somatic diseases. A situation has been arisen, in which under chronic psychosocial stress and the significant prevalence of mental disorders in the healthcare system, there is a shortage of qualified mental health professionals, a lack of equipment, and serious limitations of the legal framework. The paper considers the determinants of the relevance of expanding general practitioners’ professional competencies in the mental health of patients.