ObjectiveThe diabetes literature contains conflicting evidence on the relationship between depression and glycemic control. This may be due, in part, to the fact that past studies failed to distinguish between patients with type 1 and type 2 diabetes. Because these are actually completely different diseases that are often treated differently and consequently make different demands on patients, the relationship between glycemic control and depressed mood in type 1 and type 2 diabetes was examined separately.MethodsThe relationship between Beck Depression Inventory (BDI) scores and HbA1c, as an index of long-term glycemic control, was measured in samples of 30 patients with type 1 and 34 patients with type 2 diabetes.ResultsGroups of patients with type 1 and type 2 diabetes did not differ in mean BDI score or HbA1clevel. Correlation analysis revealed a significant positive relationship between BDI scores and HbA1cin the type 1 group (r= .44,p< .02) butnotin the type 2 group (r= −0.06,p> .05). This relationship was evident throughout the entire range of BDI scores and was not restricted to scores indicative of clinical depression. Patients with type 1 diabetes who had higher HbA1cand BDI scores reported a lower frequency of home blood glucose monitoring.ConclusionsVariations in depressive mood, below the level of clinical depression, are associated with meaningful differences in glycemic control in type 1 but not type 2 diabetes. Preliminary data analysis suggests that this effect may be mediated, at least in part, by decreased self-care behaviors in patients with more depressed mood.