The study objective was to examine the prevalence and course of depressive disorders (DDs) in teenage-onset anorexia nervosa (AN) over a period of 10 years. Fifty-one adolescents with AN and a sex- and age-matched control group (n = 51) were assessed at ages 16, 21, and 24 years. Probands and controls were examined in depth using semistructured and structured interviews. Their parents were interviewed on the occasion of the first examination. DDs were assessed using DSM-III-R criteria. Subjects with AN had a greatly increased rate of DDs (85%) of all kinds and at all ages as compared with control subjects. The risk of DD during the follow-up period from 21 up to and including 24 years could be predicted by diagnostic group status and the presence of DD during the period from 16 to 21 years, while the risk of DD during the follow-up period from 16 up to and including 21 years was solely predicted by the presence of AN at age 16 years. Long-term resolution of the eating disorder (ED) was associated with the absence of mood disorder or vice versa. Bipolar disorder (BP) occurred at roughly the expected rate (11%) among subjects (probands and controls) with major depression (MDD). In conclusion, depression is a very common comorbid problem in AN: more than four of five individuals with teenage-onset AN had at least one episode of DSM-III-R depression (MD or dysthymia [DT]) within 10 years after onset of the ED. AN appears to trigger the first episode of depression, but once it is manifest, depression predicts further depressive episodes.