Purpose: To identify and describe, in a systematic way, the various academic discourses on the rationale for SDM in mental health care, and so provide a comprehensive account of the ways in which this emerging field is being conceptualised in the research literature.Methodology: A systematic review of peer reviewed papers presenting a rationale for SDM in mental health. Relevant databases were searched from inception to July 2016. Data were analysed using a thematic analysis which aimed to identify and describe different discourses on the rationale for SDM in mental health care. Data were extracted into a standardised data extraction form which contained fields representing the developing thematic framework, study information and research methodology.Findings: Initial research returned 1616 papers, of which 175 were eligible for inclusion in this review. We developed ten distinct but interrelated themes which capture the various academic discourses on the rationale for SDM and represent some compelling arguments for SDM from a range of different perspectives including ethical, clinical, 'user' focussed, economic and political. Dominant narratives in the literature linked SDM to the recovery moment and person-centered care, and adherence and engagement with mental health services.Limitations: We are unable to make any conclusions about the strength of evidence for these rationales. Our review was restricted to peer reviewed publications, published in English.Implications: Our findings could be a useful framework to support the selection of outcome measures for SDM evaluations.Originality: There have been no systematic reviews published in this area previously.2