Definitions and factors associated with subthreshold depressive conditions: a systematic review

A Medline search was conducted of the published literature between January 2001 and September 2011. Bibliographies of the retrieved papers were also analysed.There is a wide heterogeneity in the definition and diagnostic criteria of minor and subthreshold depression. Minor depression was defined according to DSM-IV criteria. Regarding subthreshold depression, also called subclinical depression or subsyndromal symptomatic depression, between 2 and 5 depressive symptoms were required for the diagnosis, and a minimum duration of 2 weeks. Significant impairment associated with subthreshold depressive conditions, as well as comorbidity with other mental disorders, has been described.Depression as a disorder is better explained as a spectrum rather than as a collection of discrete categories. Minor and subthreshold depression are common conditions and patients falling below the diagnostic threshold experience significant difficulties in functioning and a negative impact on their quality of life. Current diagnostic systems need to reexamine the thresholds for depressive disorders and distinguish them from ordinary feelings of sadness.Despite the relevance of Major Depression (or Depressive Episode) as a highly prevalent condition in clinical practice and community settings, its subthreshold forms that do not meet current classificatory thresholds have been less studied. This in large part is due to current diagnostic systems which set the boundary of the disorder based on the presence of a certain number of symptoms. Consequently, persons falling below the threshold are not recognized in primary care settings or community surveys and often not included in biological (imaging and genetic) studies as they are considered to be distinct from those meeting the clinical threshold defined by these systems. Thus, the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition [1] requires the presence of 5 or more symptoms of depression, out of a list of 9, during at least