Aim: To perform a review of studies to identify the prevalence of depression and anxiety in adults with Type 1 diabetes mellitus compared to adults without Type 1 diabetes mellitus. Methods: A computer search was conducted using the PubMed, EBSCOhost, PsychINFO, Cochrane, CINAHL and MEDLINE from 2009 onwards. The essential information extracted from the identified publications were: participant demographics; measurement tools; prevalence of depression; diabetes-specific and non-diabetes specific risk and protective factors for depression or anxiety in people with Type 1 DM; outcomes for Type 1 DM management and complications; and relevant qualitative data. Results: An extensive literature search identified twenty-one key articles which were reviewed to provide strong evidence further supporting the notion that there is increased prevalence of comorbid depression and anxiety in Type 1 DM. Based on the literature reviewed, approximately one in five people living with Type 1 DM suffer from comorbid clinical depression, and one in four experience anxiety. There was variation in the exact rates reported between articles, however, which may be reflective of differences in methods or samples.Conclusion: The pertinence of the evidence analyzed in this review is underpinned by findings from large international studies that have shown depression results in worse health outcomes for individuals compared to any other chronic disease, including diabetes. Further, the combination of depression and diabetes leads to even poorer outcomes than does the combination of diabetes and other chronic diseases.