Epigenetics of Metabolic Syndrome as a Mood Disorder

Mood disorders comprise major depressive disorder (MDD), bipolar disorder (BD) and the milder forms of these two disorders. Reccurring MDD is also known as unipolar disorder. The distinction between unipolar and bipolar disorders was first suggested in 1957 by Leonard and was made official after support by several studies in 1980. Indeed, in 150 AD, Aretaeus of Cappadocia wrote "It seems to me that melancholia is the beginning and a part of mania". Additionally, Kraepelin, who proposed the first medical disease model in psychiatry a century ago, considered recurrent unipolar depression cases under the category of bipolar disorder and conceptualized spectrum disorders. Because today's classification systems conduct cross-sectional diagnosis, they do not consider family history, long-term characteristics and multidimensional approaches on symptoms. This method prioritizes reliability over validity and it rules out psychiatric disorders in etiology. Actually, a spectrum model which covers physical diseases is conceivable. The concept of epigenetics considers mood disorders, Alzheimer's disease, attention deficit and hyperactivity disorder, Carney syndrome, multiple endocrine neoplasia type I and II, breast and prostate cancers, carsinoid tumors, cerebrovascular and cardiovascular diseases and metabolic syndrome together. This review addressed the relationship between metabolic syndrome and mood disorders in this context along with genetic, clinical and environmental factors such as climate, geographic factors, migration and changeable lifestyles. Genetic and clinical variables are affective temperament, childhood trauma and use of antidepressants and antipsychotics.