Characteristics of studies included in the systematic review
| Study authors (year) | Country (time period) | Study design (data source) | Sample size | Depression diagnosis | Outcome diagnosis amputation |
| Black et al (2003)23 | USA (baseline interview 1993–1994; follow-up waves in 1995–1996, 1998–1999, 2000–2001) | Prospective cohort (longitudinal data from the EPESE survey) | 3050 community-dwelling Mexican Americans aged ≥65 years with type 2 diabetes | CESD scale (validated) and CIDI criteria (validated) | Self-reported in interview, grouped ‘microvascular complications’ outcome (amputation, nephropathy, retinopathy, neuropathy) |
| Gendelman et al (2009)24 | USA (2006–2008) | Cross-sectional (data from the CACTI study) | 1004 participants (n=458 type 1 diabetics) | BDI-II scale (validated) and/or self-reported use of antidepressant medication | Self-reported in interview |
| Lin et al (2010)25 | USA (baseline survey 2000–2002; follow-up telephone call 2005–2007) | Prospective cohort (data from the PEFS study) | 4623 participants with type 2 diabetes (3723 included in analysis) | PHQ-9 self-reported questionnaire (validated) | Medical record review using ICD-9 codes, physician diagnosed. Grouped ‘microvascular outcome’ (amputation, end-stage renal disease, eye complications, foot ulcers) |
| Pearson et al (2014)26 | Australia (February–August 2012) | Cross-sectional survey of patients attending podiatry clinic | 60 patients with type 1 or 2 diabetes | PHQ-9 self-reported questionnaire (validated) | Medical record review |
| Salmi et al (2011)27 | Sweden (2006), follow-up 2007–2009 | National register-based cohort | 229 956 patients prescribed antidiabetic drugs | Not reported (abstract only) but most likely ICD codes | Not reported (abstract only) but most likely ICD codes |
| Williams et al (2011)13 | USA (2000), follow-up until 2004 | Prospective cohort (Diabetes Epidemiology Registry) | 531 973 veterans with diabetes (type unknown) | ICD-9 codes | ICD-9 codes |
| Winkley et al (2007)28 | UK (2001–2003), follow-up 18 months | Prospective cohort | 253 type 1 or 2 diabetic patients attending a podiatry clinic | SCAN 2.1 diagnostic interview | Recorded by trained podiatrist |
BDI-II, Beck Depression Inventory—version two; CACTI, Coronary Artery Calcification in Type I Diabetes Study; CESD, Center for Epidemiologic Studies Depression Scale; CIDI, Composite International Diagnostic Interview; EPESE, Established Population for the Epidemiologic Study of the Elderly Survey; ICD, International Classification of Diseases; PEFS, Pathways Epidemiologic Follow-Up Study; PHQ-9, Patient Health Questionnaire version 9; SCAN, Schedules for Clinical Assessment in Neuropsychiatry.