Complex disorders such as psychiatric conditions often arise from varying combinations of genetic and environmental factors. This represents a major problem for drug development, as the cause of the disease is highly variable from person to person, and as such, drug response rates vary significantly. By examining an individual’s unique genetic risk factors, treatment response rates could theoretically be increased by improving subcategorization of individuals and personalising the administration of appropriate medications. Although genetic risk scores have been developed for this purpose, the use of epigenetic information in the form of DNA methylation remains relatively underexplored, despite the fact this epigenetic modification can simultaneously index both genetic and environmental risk factors. In this study, we will examine whether DNA methylation can be used to refine the classification individuals with complex disorders and better match affected individuals to personalised medications. In addition, we will also explore the relationship between epigenetic risk for complex disorders and measures of biochemical and metabolic traits to determine whether the epigenetic component of complex disorders is associated with changes in druggable, blood-based biomarkers.