Research examining the association between childhood abuse and depressive disorders has frequently assessed abuse categorically, thus not permitting discernment of the cumulative impact of multiple types of abuse. As previous research has documented that adverse childhood experiences (ACEs) are highly interrelated, we examined the association between the number of such experiences (ACE score) and the risk of depressive disorders. Retrospective cohort study of 9460 adult health maintenance organization members in a primary care clinic in San Diego, CA who completed a survey addressing a variety of health-related concerns, which included standardized assessments of lifetime and recent depressive disorders, childhood abuse and household dysfunction. Lifetime prevalence of depressive disorders was 23%. Childhood emotional abuse increased risk for lifetime depressive disorders, with adjusted odds ratios (ORs) of 2.7 [95% confidence interval (CI), 2.3-3.2] in women and 2.5 (95% CI, 1.9-3.2) in men. We found a strong, dose-response relationship between the ACE score and the probability of lifetime and recent depressive disorders (P<0.0001). This relationship was attenuated slightly when a history of growing up with a mentally ill household member was included in the model, but remained significant (P<0.001). The number of ACEs has a graded relationship to both lifetime and recent depressive disorders. These results suggest that exposure to ACEs is associated with increased risk of depressive disorders up to decades after their occurrence. Early recognition of childhood abuse and appropriate intervention may thus play an important role in the prevention of depressive disorders throughout the life span.