A review of etiologies of depression in COPD

There is significant evidence supporting an increased prevalence of depression in patients with COPD, but that depression is not a homogenous entity because there are multiple contributing etiologies for the depressive symptoms. Additionally the relationship between COPD and depression is neither exclusively linear, nor unidirectional. "Early onset" depression is defined as depression that develops prior to the diagnosis of COPD, often during an individual's youth. This is often reflective of a genetic vulnerability to depression which increases adolescents' risk for developing addiction to nicotine, setting up a life-long exposure to tobacco--the single greatest risk factor for the development of COPD. When COPD does develop it brings with it attendant losses, particularly in level of independent function and self image that contribute to a "reactive" depression that is not distinct from the losses experienced by those suffering with other chronic illnesses. Lastly there is increasing evidence through magnetic resonance imaging (MRI) and biochemical markers that systemic, physiologic changes associated with COPD have direct effects on the brain's vasculature that have also been associated with depression in the elderly, termed "late onset" depression. The conclusion is that the presence of depression in a COPD patient does not reflect a single pathologic pathway. Rather the two disorders each contribute to the morbidity of the other. This review discusses the evidence supporting each of these contributors and suggests that an understanding of these varying elements can direct healthcare interventions.