Comorbidity of depression in children and adolescents: Models and evidencefrom a prospective high-risk family study

Despite abundant research demonstrating the magnitude of comorbidity and it s importance in understanding childhood psychopathology, there has been lim ited empirical research designed to examine the nature and causes of comorb idity among youth. This article reviews the current literature on the magni tude and mechanisms of depressive comorbidity and presents data to exemplif y the application of high-risk and longitudinal study designs to investigat e patterns and explanations for comorbidity. A prospective family study of offspring at high and low risk for the development of anxiety was used to e xamine the specificity of familial comorbidity of depression and anxiety an d the longitudinal stability of "pure" and comorbid disorders over an 8-yea r period. Findings suggest some specificity of familial expression, as well as longitudinal specificity, of depression and anxiety. The onset of depre ssion follows the onset of most anxiety subtypes, suggesting the sequential nature of depressive comorbidity. Evaluation of mechanisms for comorbidity is important for the identification of homogeneous syndrome categories tha t will inform research designed to gain understanding of the pathogenesis o f mood or anxiety disorders. (C) 2001 Society of Biological Psychiatry.