Recurrent brief depression: the Zurich Study.

The initial conception of manic depressive illness by Kraepelin included short and mild depressive and hypomanic states in the nosologic category of affective illnesses. A longitudinal epidemiologic study in Switzerland (the Zurich Study) identified brief, but recurrent, episodes of depression with severity of symptoms, impairment, and distress equivalent to major depression. The concept of recurrent brief depression was further confirmed in recent community and general practice studies. The diagnostic criteria for recurrent brief depression require the presence of at least five of nine depressive symptoms analogous to the symptoms of major depression, yet a duration of less than 2 weeks (in general 1 to 3 days), a recurrence of at least 12 times a year, and the evidence of work impairment. The 1-year prevalence in the general population is about 5% and the lifetime prevalence 16%. Recurrent brief depression may develop into major depression and vice versa in about the same percentage of cases. It is associated with considerable suicidality and treatment-seeking and is comorbid with anxiety disorders. Patients with combined major and recurrent brief depression are more severely affected, have a higher suicide attempt rate, and have an increased frequency of treatment-seeking than patients with only one condition. Further studies are needed to establish appropriate treatment strategies.