ABSTRACT
One of the most enduring core concepts in understanding clinical depression or major depressive disorder (MDD) and how it differs from other types of depression are the so-called concepts of vegetative signs and symptoms as comprising the essential features of MDD: lethargy, sleep disturbances, concentration problems, and somatic preoccupations that are not associated with observable or detectable physical abnormalities. Aches, pains, and “u-like” symptoms are common complaints among depressed people, as is the admission: “I just do not feel that I am myself anymore.” These same signs and symptoms are reproducible in situations where patients receive interferon therapy such as when they are in treatment for hepatitis C and certain forms of cancer.1 Other symptoms in interferon therapies for these disorders can rapidly develop, such as pain, sleep disorders, and appetite problems, along with suicidal thinking. These adverse effects are considered major side effects of these treatments. Psychiatric involvement is often required or highly recommended. Interferon is a glycoprotein, in a class of compounds termed cytokines. It has functions in the human immune system that range from antiviral to the activation of natural killer cells and macrophages.2 Disorders characterized by heightened activity of the immune system such as systemic lupus erythematosus, other connective tissue disorders, and coronary artery disease are associated with a high prevalence of depression.
