The occurrence of both obesity and type 2 diabetes mellitus is rapidly increasing; according to WHO data, this can be considered as a worldwide epidemic. The obesity is one of the components of metabolic syndrome, the cluster of several risk factors of atherosclerosis such as dyslipidemia, hypertension, impaired glucose homeostasis, pro-thrombotic state and subclinical inflammation. The importance of the metabolic syndrome is confirmed by findings of the several times increased risk of both the type 2 diabetes mellitus and cardiovascular disease. Similarly, as in the case of obesity and diabetes, the incidence and prevalence of depressive disorder are still increasing and depressive disorder belongs to the most important causes of disability. The interrelations between depressive disorder and diabetes are known for a long time. Diabetics very often suffer from depression and vice versa, the depressive disorder is a significant risk factor of type 2 diabetes mellitus development and worsens the survival of diabetics. Those relationships have been recently intensively studied. Our paper reviews genetic, nutritional, metabolic and hormonal factors, contributing to the above mentioned syndrome.

        Key words: metabolic syndrome, diabetes mellitus type 2, genetic polymorphisms, oxidative stress, hyperhomocysteinemia, n-3 polyunsaturated fatty acids.