Aims. Depression can significantly affect quality of life and is associated with higher rates of medical comorbidities and increased mortality following surgery. Although depression has been linked to poorer outcomes following orthopaedic trauma, total joint arthroplasty and spinal surgery, we wished to examine the impact of depression in elective total shoulder arthroplasty (TSA) as this has not been previously explored. . Patients and Methods. The United States Nationwide Inpatient Sample (NIS) was used to identify patients undergoing elective TSA over a ten-year period. Between 2002 and 2012, 224 060 patients underwent elective TSA. Results. Among the identified patients who had undergone TSA, 12.4% had a diagnosis of a history of depression. A diagnosis of depression was twice as common in women compared with men (16.0% vs 8.0%, p < 0.001), and more frequent in those with low income and Medicaid insurance (p < 0.001). A diagnosis of depression was an independent risk factor for post-operative delirium (odds ratio (OR) 2.29, p < 0.001), anaemia (OR 1.65, p < 0.001), infection (2.09, p = 0.045) and hospital discharge to a placement other than home (OR 1.52, p < 0.001) . Conclusion. A history of clinical depression is present in 12.4% of patients undergoing elective TSA and the disease burden is projected to increase further in the future. Depression is often underdiagnosed and pre-operative screening and appropriate peri-operative management of patients is encouraged. Take home message: The awareness that clinical depression is associated with increased complications following total shoulder arthroplasty provides physicians an opportunity for early intervention in this at-risk population. Cite this article: Bone Joint J 2016;98-B:818–24