Prevalence of depression in patients with chronic obstructive pulmonary disease: a systematic review

Background-Patients with chronic obstructive pulmonary disease (COPD) have repeatedly been characterised as a population of chronically ill patients w ith a higher than normal prevalence of depression. Susceptibility for depre ssion has been noted in patients with certain other chronic conditions. Thi s systematic review was conducted to achieve a more definite answer to the question: do patients with COPD show a higher than normal prevalence of dep ression? Methods-Studies in English language journals were retrieved by an electroni c search over the period from 1966 to December 1997 and by an extended sear ch of reference Lists, and were included or excluded according to a system of diagnostic and methodological criteria. Results-Ten studies were included, of which only four had a case-control de sign. Three of the case-control studies reported an increased prevalence of depression among patients with COPD which was statistically significant in only one. The fourth controlled study found a significantly increased depr ession score among COPD patients. Of the remaining six uncontrolled studies three found a high baseline prevalence of depression among their study gro up. Conclusions-An association between COPD and depression was found in the fou r controlled studies. The two methodologically best conducted studies that did not detect a statistically significant higher prevalence lacked power. The two studies that did find a significant association used a questionable depression measure. The prevalence of depression was high compared with ge neral population figures in three of six non-controlled studies. The empiri cal evidence for a significant risk of depression in patients with COPD rem ains inconclusive, due to the poor methodological quality of most of the pu blished studies, the lack of studies with an adequate sample size, and vari ability in instruments and cut off scores used to measure depression.