Subthreshold depression and depressive disorder: clinical characteristics of general medical and mental health specialty outpatients.

OBJECTIVE: The authors examined the clinical significance of depressive symptoms below the threshold for depressive disorder in outpatient samples.
METHOD: The subjects were 775 adult patients with current depressive disorder, 1,420 patients with subthreshold depression, and 1,767 hypertensive patients with and without depression, all of whom were visiting the offices of mental health specialists and general medical care providers in three U.S. cities. Data on demographic characteristics, severity of depression, extent of psychiatric and medical comorbidity, family psychiatric history, and treatment history for the patients with depressive disorder and those with subthreshold depression were compared.
RESULTS: The percentage of patients with subthreshold depression who had a family history of depression (41%) was nearly as high as that of the patients with depressive disorder (59%). The two groups of patients had similar levels of medical and psychiatric comorbidity except for anxiety disorders, which were greater among the patients with depressive disorder. Among the hypertensive patients in the general medical sector, those with subthreshold depression were more similar to those with depressive disorder than to the nondepressed hypertensive patients. Treatment rates were considerably lower for patients with subthreshold depression than for patients with depressive disorder in the general medical sector, but they were similar in the mental health specialty sector.
CONCLUSIONS: In these outpatients, subthreshold depression appeared to be a variant of affective disorder and was treated as such in the mental health specialty sector but not in the general medical sector. The findings emphasize the importance of treatment outcome studies of patients with subthreshold depression.