In this chapter, we argue that progress in the field of mental health has been constrained by a reliance on assumptions which often lack a credible evidence-base. These assumptions are, from our perspective, either
untested or, worse, untestable. In addition to lacking empirical support, the assumptions are frequently implicit and left unstated, although this does not appear to diminish the influence on the research and practice
that occurs (Carey, Huddy, & Griffiths, 2019). It is our position that many of these assumptions could, in fact, be characterised as myths. After explaining what we mean by the term “myth” in this context, we will describe why we think it is problematic for myths to inform mental health research and practice. We will also provide some examples of concepts and practices that we believe fit into the category of myth.