This chapter describes how clinical psychologists work with medical professionals to treat disorders, help patients to cope with the stress of medical conditions, and to adhere to medical treatment recommendations. It also describes factors that contribute to disease, focusing on relationships between psychosocial factors (such as stress and unhelpful patterns of thinking) and physical factors (such as nervous system activity, circulation, and immune system functioning). The chapter also includes a description of behavioral and psychological risk factors that enhance the likelihood of illnesses such as cardiovascular disease, chronic pain, and cancer. Also discussed are programs for preventing or minimizing the impact of those risk factors.

Suicide is a complex public health problem driven by a multitude of biopsychosocial factors and is the result of gene–environment interactions. Psychosocial variables like chronic stress and trauma have biologic ramifications and can contribute to various forms of pathophysiology, dysregulation, and degradation, represented by allostatic load (AL). AL is the wear and tear that stress exerts on the body, and it has been associated with mental health problems and suicide. Fortunately, there are pharmacological and non-pharmacological interventions that may be effective at reducing AL and reversing its effects. Incorporating AL into efforts to promote early risk identification, prevention, and treatment of suicide is an important consideration. Critical next steps are identifying which AL biomarkers are most malleable, which effective treatments reduce AL, and if these reductions of AL are associated with decreased suicide.