PURPOSE: Depression is associated with lowered work functioning, including absences, impaired productivity, and decreased job retention. Few studies have examined depression symptoms across a continuum of severity in relationship to the magnitude of work impairment in a large and heterogeneous patient population, however. We assessed the relationship between depression symptom severity and productivity loss among patients initiating treatment for depression. METHODS: Data were obtained from patients participating in the DIAMOND (Depression Improvement Across Minnesota: Offering a New Direction) initiative, a statewide quality improvement collaborative to provide enhanced depression care. Patients newly started on antidepressants were surveyed with the Patient Health Questionnaire 9-item screen (PHQ-9), a measure of depression symptom severity; the Work Productivity and Activity Impairment (WPAI) questionnaire, a measure of loss in productivity; and items on health status and demographics. RESULTS: We analyzed data from the 771 patients who reported being currently employed. General linear models adjusting for demographics and health status showed a significant linear, monotonic relationship between depression symptom severity and productivity loss: with every 1-point increase in PHQ-9 score, patients experienced an additional mean productivity loss of 1.65% (P <.001). Even minor levels of depression symptoms were associated with decrements in work function. Full-time vs part-time employment status and self-reported fair or poor health vs excellent, very good, or good health were also associated with a loss of productivity (P <.001 and P=.045, respectively). CONCLUSIONS: This study shows a relationship between the severity of depression symptoms and work function, and suggests that even minor levels of depression are associated with a loss of productivity. Employers may find it beneficial to invest in effective treatments for depressed employees across the continuum of depression severity.