Objectives: To evaluate evidence, in a community sample, for discriminant validity between major depression (MDD) and dysthymia (Dy) in children and adolescents and to examine differential consequences of the 2 disorders for functioning.
Method: The National Institute of Mental Health (NIMH) Methods for the Epidemiology of Child and Adolescent Mental Disorders (MECA) study consists of probability samples of youths. Data for this study are derived from interviews with 1,285 complete parent-youth pairs aged 9 to 17 years from 4 geographic areas in the United States. Youths with MDD were contrasted with those with Dy and those with both (MDD-Dy) on the NIMH Diagnostic Interview Schedule for Children, Non-Clinician Children's Global Assessment Scale, Columbia Impairment Scale, and the Service Utilization and Risk Factors Module.
Results: Groups with MDD, Dy, or MDD-Dy did not differ on sociodemographic, clinical, or family and life event variables. Youths with combined MDD-Dy were significantly less competent and more impaired than youths with either disorder alone.
Conclusions: The findings do not provide support for the differentiation of MDD and Dy but strongly suggest the importance of addressing the needs of youths who meet criteria for both MDD and Dy because this combination is likely to be both serious and disruptive of normal developmental processes.