Socioeconomic deprivation is associated with negative health outcomes including mental health. This thesis explores associations between socioeconomic deprivation and psychopathology in adults, both globally, and locally, presented across three chapters. A systematic review of literature published over the past ten years reporting on prevalence rates of psychopathology in adults experiencing homelessness is presented in Chapter 1. Thirty-one studies were included in the review, with a pooled sample of 53,299 individuals. Robust evidence of an association between homelessness and psychopathology was found, in studies conducted in Europe, North America, Australasia, Asia and Africa. Rates of psychopathology were found to be considerably higher than general population estimates, which is consistent with findings documented in a previous systematic review. An empirical study, presented in Chapter 2, investigated associations between multiple types of deprivation, measured at the neighbourhood-level, and psychiatric admissions, across North Wales over a six-year period. Multiple deprivation was highly significantly associated with incidence of cases admitted, with areas of greater overall deprivation predictive of higher admissions. This relationship was stronger for people with psychosis-related conditions than for those with other mental health conditions. Chapter 3 considers the results of both articles presented in the previous chapters, and provides a discussion of theoretical and clinical implications, as well as personal reflections regarding the research process and results.