Mood disorders in children and adolescents: an epidemiologic perspective.

Epidemiologic studies show that major depression is comparatively rare among children, but common among adolescents, with up to a 25% lifetime prevalence by the end of adolescence. Mania is much less common, with no more than a 2% lifetime prevalence by the end of adolescence. Developmental studies that include assessments of both hormonal changes and social changes through the pubertal transition are needed to investigate joint biological and environmental influences on the emergence of the gender difference in depression in puberty. Although subthreshold mood disorder symptoms are common, controversy exists about their clinical significance. This controversy is made more complex by methodologic uncertainties regarding inconsistent symptom reports obtained from parents, teachers, and children and by the pervasive existence of comorbidity. Retrospective reports about age of onset in adult studies suggest that at least 50% of youngsters with major depression and 90% of those with mania continue to have adult recurrences. These recurrences are mediated by adverse role transitions, such as truncated educational attainment and teenage childbearing, that typically occur before the time of initial treatment. Aggressive outreach and early treatment aimed at preventing the occurrence of adverse role effects might help decrease the persistence of child and adolescent mood disorders. Long-term follow-up studies are needed to resolve current uncertainties regarding nosology, methodology, and long-term treatment effects. Innovative epidemiologic research designs aimed at more quickly providing provisional information are also needed to advance understanding of long-term developmental processes.

Comorbidity of depression in children and adolescents: models and evidence from a prospective high-risk family study.

Despite abundant research demonstrating the magnitude of comorbidity and its importance in understanding childhood psychopathology, there has been limited empirical research designed to examine the nature and causes of comorbidity among youth. This article reviews the current literature on the magnitude and mechanisms of depressive comorbidity and presents data to exemplify the application of high-risk and longitudinal study designs to investigate patterns and explanations for comorbidity. A prospective family study of offspring at high and low risk for the development of anxiety was used to examine the specificity of familial comorbidity of depression and anxiety and the longitudinal stability of "pure" and comorbid disorders over an 8-year period. Findings suggest some specificity of familial expression, as well as longitudinal specificity, of depression and anxiety. The onset of depression 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 that will inform research designed to gain understanding of the pathogenesis of mood or anxiety disorders.