Companies and countries are appropriately obsessed with bending the curve of healthcare costs. 

Starbucks paid more for health insurance than for coffee, and the three domestic automakers spent more on healthcare than on steel.

What is less recognized is that stress and depression increase not just the costs associated with treating behavioral health problems but also the incidence of other costly physical diseases. At least two mechanisms help explain this connection between mental and physical health.

First, psychological well-being and social determinants of health can directly affect the likelihood of an individual engaging in healthful behaviors and self-care such as eating and drinking alcohol in moderation, regular exercise, and avoiding smoking and drug use. People with mental and substance use disorders, as well as those who have experienced psychological trauma, are at higher risk for chronic diseases such as diabetes, heart disease, and musculoskeletal problems.

Second, research shows that stress and depression cause physiological changes, such as metabolic, endocrinal, and inflammatory shifts, that are markers and predictors of disease. The idea that the mind affects the body is scarcely new, but the emerging science of psychoneuroimmunology is revealing in detail the pathways that link changes in the brain to effects on the immune system (see sidebar, “The promise of precision psychiatry”).

A paper linking stress, depression, the immune system, and cancer noted that “many studies” showed “that psychological stress can down-regulate various parts of the cellular immune response. Communication between the CNS [central nervous system] and the immune system occurs through chemical messengers secreted by nerve cells, endocrine organs, or immune cells, and psychological stressors can disrupt these networks.”1