Diabetes mellitus is a disease with complex neuro-endocrine pathogenesis, in which the main role is played by a decrease in insulin production by islet cells of the pancreas (absolute insulin deficiency). However, along with this, it is also necessary to reckon with a possible increase in the need for insulin, which develops as a result of damage to the central nervous system, pituitary gland and adrenal glands (relative insulin deficiency). The consequence of a lack of insulin is deep metabolic disorders, and primarily carbohydrate metabolism. The incidence of diabetes, very low in childhood and adolescence, gradually increases over the years and mainly occurs in people between 50-60 years of age. Diabetes is more often affected by women. When analyzing the causes of the development of diabetes mellitus, it is rarely possible to establish some external point with which the occurrence of the disease could be reliably associated. In some cases, when the development of the disease was directly preceded by a psychological trauma, we can assume its primary and main etiological significance. This assumption is confirmed by long-known clinical observations that showed a worsening of diabetes with the addition of negative emotional factors (for example, fright, death of loved ones, troubles in the service, etc.). However, with the development of diabetes mellitus after mental trauma, we usually cannot solve the question of whether it was the primary and main etiological factor, or whether it contributed only to the identification of the latent disease. The much more convincing etiological significance of mental factors – long-term mental stress and massive mental trauma – was manifested in the increase in the incidence of diabetes after the end of World War II. Another indicator of the role of mental overstrain and repeated mental trauma is the very high incidence of diabetes in the United States of America. So, according to recent years, the number of patients with diabetes in the United States exceeds 1 million people, and mortality from it took 8th place among other diseases. We do not currently have data on the incidence of diabetes in other capitalist countries, but according to materials available until the last war, the incidence in England and Germany was also very high, although it did not reach the figures observed in the United States. In a small part of cases, a possible cause of the disease are infections (for example, flu, tonsillitis), leading to the development of infectious toxic lesions of the islet apparatus. However, it is always necessary to reckon with the possibility of having an already existing, latent insufficiency of the insular apparatus, and the infection should be considered as an additional etiological factor that revealed this insufficiency. In very rare cases, diabetes mellitus develops after the surgical removal of a significant part of the pancreas produced due to adenoma or carcinoma of the islets with symptoms of hyperinsulinism. There are a number of clinical and experimental data supporting the assumption of the etiological significance of overeating, and especially carbohydrate-rich foods, in the development of diabetes. So, with insufficiency of the islet apparatus caused by the removal of part of the pancreas (dog) or alloxap (rats), but in the absence of obvious diabetes, overfeeding with carbohydrates can cause the development of diabetic disorders. Currently, the parenteral administration of large amounts of glucose in cats caused the development of persistent diabetes as a result of damage to their islet apparatus. The clinic also has to observe the development of diabetes after applying large amounts of glucose for other diseases, which is consistent with the well-known facts of the deterioration of existing diabetes from excessive consumption of carbohydrates. High incidence of diabetesobesity, in which the inevitably arrival of energy material exceeds consumption, is an additional confirmation of the probable auxiliary role of overeating, which is often combined with the influence of insufficient muscle work.