Old diseases, posing new problems. That’s how Prof Licinio, Director of Translational Medicine and Head of the Mind and Brain Theme at the South Australia Health and Medical Research Institute, Flinders University in Adelaide Australia, introduced depression and obesity.

He highlighted multiple reasons why these conditions merit joint consideration and common study. The diseases frequently coexist and there can be a two-way causal relationship: being obese can lead to depression and having depression can lead to obesity. Brain circuitry controlling mood and food intake are intimately linked, and indeed Prof Licinio said he believes that many of the pathways important to these disorders are one and the same.

Much in common

Prof Licinio reminded the audience of the prominence of these conditions in modern society. He said headlines frequently draw attention to skyrocketing rates of obesity, and he pointed out that depression is increasingly seen and diagnosed at younger and younger ages.

According to Prof Licinio, obesity and depression are far more intertwined than is widely appreciated. While sedentary-life-styles and an obesogenic food environment are facts known to contribute to the obesity epidemic, Prof reminded the audience that over-eating is often a form of self-medication for mood disorders such as depression.

Prof Licinio said both conditions may be a consequence or manifestation of chronic stress, where hypothalamic control on glucocorticoid and cortisol levels becomes deranged.

Prof Licinio described some of clinical and scientific research that is trying to piece together common mechanisms in order to understand relationships between depression and obesity. He has studied the so-called “satiety” hormone leptin - produced by adipose cells and involved in moderating food intake – looking at families with rare genetic conditions of leptin deficiency and showing that leptin replacement therapy can reverse the severe obesity that characterizes these cases. He described studies in animal models which suggest that leptin may help down-regulate chronic stress and support neurogenesis in the hypothalamus. The audience also heard about research into the role of cortisol and immune mediators in mood disorders.

Prof Licinio said that pharmacogenetic studies looking at phenotypes and genotypes in different diseases not only help identify potential new drug targets but may help highlight common ground between depression and obesity. And he added his hopes that genomics and exon genotyping will provide clues that can be used to mount what he called a “multifrontal” war on psychiatric illnesses.