ABSTRACT
This chapter focuses on a variety of biological mechanisms that have also been implicated in the production of depression in some patients. It also focuses on the difficulties involved in isolating biological from other depressogenic mechanisms. The chapter summarizes the evidence to support a direct relationship between specific physical illnesses and depression and consider the biological mechanisms that have been implicated. It emphasizes the illnesses in which specific mechanisms have been postulated to account for their association with depression. Biological mechanisms that have been implicated in the production of depression in the medically ill include the effects of pharmacologic agents and metabolic disturbances associated with specific medical disorders. The chapter determines whether biological disturbances associated with a medical illness are specifically linked to depression. Biological mechanisms again may be suspected when depression is more prevalent in one illness than in others with a similar prognosis, severity, or level of disability.
