Implications of obesity and medical illness for major depression – a different endophenotype of major depression in obese patients?

We examined the prevalence of medical comorbidity in depression compared with healthy controls and evaluated the association between obesity and HPA axis function and treatment response in depression. The data was evaluated from a 1000/1000 case-control study for unipolar recurrent depression and from the Munich Antidepressant Response Signature (MARS) project with 350 inpatients, who were followed by psychopathological, somatic and HPA system function measurements during their hospitalization. The patients in the unipolar depression group showed higher rates of hypertension, type 2 diabetes mellitus and obesity compared with psychiatric healthy controls. Depressed patients additionally had a higher body-mass-indexes, waist-to-height ratios, heart rates, creatine and urea levels and lower iron and HDL cholesterol levels. The obese depressed patients showed a different depression phenotype, as determined by less severe psychopathology, lower cortisol levels after dexamethasone and a blunted cortisol response after hCRH in the Dex/CRH-test on admission and discharge; they also showed a slower response to antidepressants and reduced weight gain during psychopharmacological therapy compared with non overweight patients. The results suggest, that depression is associated particularly with components of the metabolic syndrome and obesity. Obese depressed patients show a different phenotype of depression with respect to psychopathology, HPA axis and treatment response.