This is a meta-analysis that was published in 2001. [1]
A total of 42 eligible studies were identified; 20 (48%) included a nondiabetic comparison group. In the controlled studies, the odds of depression in the diabetic group were twice that of the nondiabetic comparison group (OR 5 2.0, 95% CI 1.8 –2.2) and did not differ by sex, type of diabetes, subject source, or assessment method. The prevalence of comorbid depression was significantly higher in diabetic women (28%) than in diabetic men (18%), in uncontrolled (30%) than in controlled studies (21%), in clinical (32%) than in community (20%) samples, and when assessed by self-report questionnaires (31%) than by standardized diagnostic interviews (11%).
1 Anderson R, Freedland K, Clouse RE, et al. The Prevalence of Comorbid Depression. Diabetes Care 2001;24:1069–78.