In this chapter we introduce the topic and aims of the book and define key terms such as anxiety, corpus linguistics and discourse. We provide the motivation for writing the book and outline other studies which have examined language in healthcare contexts, in particular focusing on studies which have looked at healthcare forums and/or mental health issues, as well as studies which have used corpus linguistics techniques for corpus-assisted discourse analysis. We then outline the research questions which drive the analysis in the book. We introduce the corpus that we worked with and discuss ethical issues in dealing with online data, as well as issues relating to data processing. We also provide a description of the tools and techniques that we used to carry out our analysis. We then reflect on our own position in relationship to the topic we are researching. Finally, we provide an outline of the remaining chapters of the book.