OBJECTIVE: The objective of this study is to examine the prevalence of depression and its related factors including quality of life, brain-derived neurotrophic factor (BDNF), and vitamin D in patients with systemic lupus erythematosus (SLE). METHODS: Depression was assessed using the center for epidemiologic studies depression (CES-D) scale. Disease activity, disease-related organ damage, the EuroQol-5 dimensions (EQ-5D), sociodemographic features, and laboratory tests including serum vitamin D level were surveyed. Serum BDNF was measured using an enzyme-linked immunosorbent assay. RESULTS: Depression was observed in 22.8% of 180 SLE patients (n=41). Patients with marital status of single/divorced/separated/widowed, a higher patient global assessment (PGA) score, and extreme pain/discomfort showed significant association with depression. The EQ-5D index showed negative correlation with CES-D score (r=-0.56, p<0.05). In each EQ-5D dimension, depression showed significant association with moderate to severe problems in self-care and usual activities, and extreme pain/discomfort. Serum BDNF levels were not associated with depression (p=0.75) but associated with SLE disease activity index (SLEDAI; r=-0.21, p<0.05). Serum vitamin D levels were not associated with depression (p=0.60) but showed negative correlation with SLEDAI (r=-0.23, p<0.05) and mean glucocorticoid dose over the previous 3 months (r=-0.21, p<0.05) after adjustment for use of vitamin D supplement. CONCLUSION: Depression was prevalent in patients with SLE and was associated with low quality of life, and a higher PGA but not with SLEDAI. Serum BDNF and vitamin D levels were not associated with depression but showed snegative correlation with SLEDAI.