Impact of medical comorbidity in biomarker discovery for major depressive disorder

The interaction between major depressive disorder (MDD) and other medical conditions is increasingly recognized as an important factor for clinical management and for biomarker development. Many common medical conditions have a bidirectional epidemiologic relationship with MDD that may have roots in shared pathophysiologic, environmental, and psychosocial factors. Furthermore, depression is increasingly recognized as a systemic disease. Understanding this relationship is challenging because of the immense variability between patients with MDD and also within other medical disorders themselves. This includes not only specific symptoms, but also disease severity, duration, disability, and treatment resistance.