C chronic physical pain. The comorbidity of chronic pain and chronic depression is so common and the conditions are so interwoven that it is difficult to pinpoint which usually comes first or whether one causes the other; still, the correlation is clear. Almost half of all people with depression experience comorbid somatic symptoms of pain and discomfort. 1, 2 Depression is often correlated with headaches, back pain, chest pain, gastrointestinal discomfort, and other chronic aches and pains. Depression that accompanies chronic pain disorders only worsens the condition, contributing more disability and impairment of daily functioning. 3 The presence of a chronic pain disorder may also complicate or even preclude diagnosis of depression, or vice versa.

Although the exact relationship between pain and depression is undefined, their comorbidity often operates in 3 different ways. 4 Comorbid pain and depression may be attributed to a heightened susceptibility to both physical and psychological dysphoria and a tendency for psychological stress to magnify physical dysphoria. The connection between pain and depression may also manifest as a maladaptive psychological or behavioral response to pain experienced in the early stages of a condition that has since resolved; in this situation, the dysfunctional psychological and behavioral responses continue despite the cessation of physical pain. Another way that pain and depression function together occurs when pain becomes a significant physical and psychological stressor and produces or aggravates a psychological condition. When treating depression, it is important that both the physical and psychological aspects be addressed. Full re-