Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycemia, which is caused by failure in insulin secretion and/or action and it triggers various acute and chronic complications in patients. The central nervous system complications of diabetes are known as "diabetic encephalopathy". The complications due to chronic hyperglycemia and impaired insulin functions are designated "primary diabetic encephalopathy", other complications due to vascular diseases or hypoglycemic episodes, which depend on intense insulin treatment are named "secondary diabetic encephalopathy". Diabetes was shown to be associated with several cerebrovascular, neurochemical and electrophysiologic changes on the central nervous system. Increase in depression and anxiety levels, disorders in cognitive functions like problem solving, attention, information interpreting and saving and changes in pain perception have been reported in experimental diabetic animals. On the other hand, there are some clinical reports which indicated the sleeping disorders, somatization, nervous and depressive mood, defects in cognitive functions like learning, memory, problem solving hyperalgesia and allodynia in Type-I diabetic patients and impaired cognitive functions, decreased discrete reasoning and complex psycomotor activity, and higher dementia risk in Type-II diabetic patients. Reports suggested that insulin could not prevent the mentioned psychiatric and cognitive disorders alone, because such disorders also developed in Type-I diabetic patients who used insulin regularly. Considering the increase in the rate of diabetes pravelance, approaches to treat psychiatric and cognitive disorders which decrease the life quality of diabetic patients gain more importance.