Childhood-onset dysthymic disorder. Clinical features and prospective naturalistic outcome

To characterize the clinical presentation, course, and outcome of childhood-onset dysthymic disorder and assess the predictive validity of this diagnosis.

As part of a longitudinal prospective study, school-age, clinically referred youngsters (n = 55) whose first depression was dysthymic disorder and a comparison group of youngsters (n = 60) whose first affective episode was major depressive disorder (MDD) were repeatedly examined during a 3- to 12-year interval. The diagnoses were based on DSM-III criteria.

Dysthymic disorder was associated with earlier age at onset than MDD, similarly frequent symptoms of affective dysregulation, but low rates of anhedonia and neurovegetative symptoms and greater overall risk of any subsequent affective disorder. The affective disorders that dysthymic children developed, including first-episode MDD (76%) and bipolar disorder (13%), far outnumbered nonaffective conditions. After the first episode of MDD, the clinical course of the initially dysthymic youths was similar to the course of the comparison patients with regard to rates of recurrent major depression, bipolar disorder, and certain nonaffective disorders.

Childhood-onset dysthymic disorder is an early marker of recurrent affective illness. Although on long-term follow-up, dysthymic disorder and MDD are associated with similar rates of certain outcomes, there exist sufficient differences to warrant diagnosis of each disorder. Dysthymic children who have subsequent mood disorders are most likely first to have an episode of MDD, and that episode appears to be the "gateway" to recurrent affective illness. The interval between the onset of dysthymia and the first major depression provides a window of opportunity for intervention and possible prevention of later episodes.