Understanding the heterogeneity of depression through the triad of symptoms, course and risk factors: a longitudinal, population-based study

Background: There is an ongoing research effort to test if depression is a homogeneous clinical syndrome and to identify valid and useful subtypes bas ed on the number and nature of depressive symptoms. This study summarizes t he patterns of depressive symptoms evident in a prospective study of the ge neral population and examines the validity of potential subtypes by studyin g their course and etiologic heterogeneity, Methods: A general population s ample of 1920 adults (aged 18-96) from the Baltimore Epidemiologic Catchmen t Area (ECA) follow-up study (1981 to 1993/6) were examined. Data on diagno ses, symptoms, course and risk factors were collected using the Diagnostic Interview Schedule (DIS). Latent class analysis was applied to summarize sy mptom patterns. Course characteristics and risk factor profiles were compar ed among potential subtypes based on the number of symptom groups or sympto m patterns. Logistic regression models were used to examine the etiologic h eterogeneity among potential subtypes based on symptoms. Results: The numbe r of symptom groups gave the most efficient insight into differential etiol ogic processes, Severe depression (7-9 symptom groups) was associated with female gender, family history of depression but not with stressful life eve nts before the onset of the first episode. Moderate (5-6 symptom groups) an d mild depression (3-4 symptom groups) were associated with family history of depression, stressful life events before the onset, but not with female gender. The latent class model generated patterns of depressive psychopatho logy as follows: anhedonia, suicidal, psychomotor, and severely depressed s ubtypes. The Anhedonia subtype showed a course and risk factor profile dist inct from the others. Limitations: The measurement of psychopathology was b ased on self-reported DIS interviews instead of psychiatric assessments. Re call or report bias cannot be excluded in the ascertainment of family histo ry and stressful life events. Conclusions: Depression is heterogeneous, eve n below the threshold of syndromal diagnosis. The severity of an episode ap pears to be more informative than the pattern of symptoms, with the possibl e exception of a putative anhedonic subtype. (C) 2000 Elsevier Science B.V. All rights reserved.