Interaction Between Depression, Obesity, and Type 2 Diabetes: A Complex Picture.

Depression plays an important role in the pathogenesis and treatment of obesity and type 2 diabetes (T2D). However, its relevance is frequently unrecognized by clinicians and researchers. The purpose of this review is to present a critical analysis of the evidence linking depression and metabolic disorders and to highlight the practical implications of this complex relationship. Evidence obtained from epidemiological, basic, clinical and controlled studies demonstrate that the association goes beyond a random phenomenon. Epidemiological studies have rendered controversial results due to the lack of control of the confounding variables and the bidirectional relationship that exists between the outcomes and the conditions that modulate the association (i.e. socioeconomic status). Animal and human studies have been useful to define the anatomic substrates and physiologic processes that participate in the association, but, the evidence is preliminary in many areas (i.e gene × environmental interactions). Controlled studies have shown the strong impact that treatment of depression has on body weight and the large effect that has the correction of excess body weight on the depression-related symptoms. Practical implications of the depression-obesity duet include the training of the health providers to assess and treat these conditions in a concomitant manner, the need for translational medicine projects and the application the systems biology approach to fill the existing gaps of knowledge.