For instance, chronic non-infectious diseases such as diabetes mellitus (54), coronary artery disease (55), hypertension (56), and chronic obstructive pulmonary disease (57) are known to lead to increased levels of cytokines (e.g., interleukin-2, tumor necrosis factor), which can induce depressive symptoms (58, 59). Here, TNF is linked to chronic obstructive pulmonary disease.