Prevalence of depression and depressive symptoms among outpatients: a systematic review and meta-analysis.

Depression and depressive symptoms are common mental disorders that have a considerable effect on patients' health-related quality of life and satisfaction with medical care, but the prevalence of these conditions varies substantially between published studies. The aim of this study is to conduct a systematic review and meta-analysis to provide a precise estimate of the prevalence of depression or depressive symptoms among outpatients in different clinical specialties.