1: Introduction

(SUD) is formally recognised as a primary mental health condition in the Diagnostic and Statistical Manual (DSM) of mental health disorders. The last major revision of this manual, the DSM-5, is accepted as a standard classification for mental health disorders in the United States (First et al., 2021). It informs current understanding of the behavioural, physical and psychological effects of SUD (Robinson & Adinoff, 2016; Witkiewitz et al., 2020) and is internationally influential in how it is diagnosed, researched and treated (Hasin et al., 2013). The DSM-5 defines different levels of SUD which are diagnosable based on the number of symptoms exhibited by an individual. While not explicitly referenced in the DSM for SUD, the term ‘addiction’ is principally considered as a severe form of SUD and as such is common parlance in literature, research and within healthcare settings (McLellan, 2017; NHS, 2024; Volkow & Blanco, 2023). Other systems of classification exist, for example, the International Classification of Diseases; however, there is a far greater body of work generated using the DSM, making it the predominant classification.