Prevalence, 20-month incidence and outcome of unipolar depressive disorders in a community sample of adolescents

Background. This article presents prospective longitudinal findings on prevalence, incidence, patterns of change and stability of depressive disorders in a community sample of 1228 adolescents.

Methods. Data were collected at baseline and follow-up (20 months later) in a representative population sample of 1228 adolescents, aged 14-17 at baseline. Diagnostic assessment was based on the Munich Composite International Diagnostic Interview (M-CIDI).

Results. The overall cumulative lifetime incidence of any depressive condition was 20.0 % (major depressive disorder (MDD), 12.2 %; dysthymia, 3.5 %; subthreshold MDD, 6.3 %), of which about one-third were incident depressions in the period between baseline and follow-up. Depressive disorders rarely started before the age of 13. Females were about twice as likely as males to develop a depressive disorder. Overall, the 20-month outcome of baseline depression was unfavourable. Dysthymia had the poorest outcome of all, with a complete remission rate of only 33 % versus 43 % for MDD and 54 % for subthreshold MDD. Dysthymia also had the highest number of depressive episodes, and most psychosocial impairment and suicidal behavioural during follow-up. Treatment rates were low (8-23%). Subthreshold MDD associated with considerable impairment had an almost identical course and outcome as threshold MDD.

Conclusions. DSM-IV MDD and dysthymia are rare before the age of 13, but frequent during adolescence, with an estimated lifetime cumulative incidence of 14%. Only a minority of these disorders in adolescence is treated, and more than half of them persist or remit only partly.