Clinical features and classification The term depression describes a spectrum of mood disturbance ranging from mild to severe and from transient to persistent. Depressive symptoms are continuously distributed in any population but are judged to be of clinical significance when they interfere with normal activities and persist for at least two weeks, in which case a diagnosis of a depressive illness or disorder may be made. The diagnosis depends on the presence of two cardinal symptoms of persistent and pervasive low mood and loss of interest or pleasure in usual activities. Criteria for major depression* Five or more of the following symptoms during the same two week period representing a change from normal View this table: In this window In a new window Adjustment disorders are milder or more short lived episodes of depression and are thought to result from stressful experiences. Major depressive disorder refers to a syndrome that requires the presence of five or more symptoms of depression in the same two week period. View larger version: In this window In a new window “Neurotic” symptoms, including depression, are continuously distributed in the UK population View larger version: In this window In a new window The association between depression and mortality after myocardial infarction Dysthymia covers persistent symptoms of depression that may not be severe enough to meet the criteria for major depression, in which depressed mood is present for two or more years. Such chronic forms of depression are associated with an increased risk of subsequent major depression, considerable social disability, and unhealthy lifestyle choices such as poor diet or cigarette smoking. Manic depressive (bipolar) disorder relates to the occurrence of episodes of both major depression and mania. Further reading Kessler RC, McGonagle KA, Zhao S, Nelson CB, Hughes M, Eshleman S, et al. Lifetime and 12-month prevalence of DSM-IIIR psychiatric disorders in the United States: results of the national comorbidity surveyArch Gen Psychiatr 1994;518–19 Rodin G, Craven J, Littlefield C Depression in the medically ill: an integrated approach New York NY: Brunner/Mazel 1991 Royal College of Physicians, Royal College of Psychiatrists The psychological care of medical patients: recognition of need and service provision London: RCP, RCPsych 1995