The Zurich Study. XI. Is dysthymia a separate form of depression? Results of the Zurich Cohort Study.

Dysthymia was assessed in the prospective Zurich Cohort Study of young adults. The 1-year prevalence rate was around 3% if no exclusion criteria were applied. Pure dysthymics without major or recurrent brief depression accounted for about 1%. Most cases of dysthymia met the symptom criteria for major depressive disorder (MDD) and were characterized by a more continuous course. However, evidence presented in this paper suggests that a diagnosis separate from MDD is not warranted. The family history of dysthymic subjects did not differ from major depressives. The smaller group of primary dysthymics, on the other hand, did not differ from controls as regards family history for treated depression. The low prevalence rates, taken together with methodological problems involved in assessing dysthymia and the lack of a distinct course, suggest that dysthymia does not constitute a valid subtype of depression in an age group of 20-30 years of the community. Dysthymia belongs to the wide spectrum of major depressive syndromes and represents only a subgroup characterized by specific course characteristics.