Statins lower levels of ‘bad’ cholesterol, and stop or slow the progression of cardiovascular disease (CVD). Statin adherence is associated with lower risk of CVD events (e.g. heart attack/stroke), and death from CVD or any cause (Martin-Ruiz 2018; Vrecer 2003). However, after two years, only around 25% of patients take statins as prescribed (Brown 2011). Despite this, there is a relative lack of research into psychological determinants of statin adherence, or categorisations of the behavioural components of effective statin interventions. The proposed PhD will use behavioural science approaches and qualitative and quantitative methods to identify how determinants of non-adherence differ between different patient groups and between individuals. This will inform the design of a scalable adherence intervention, tailored to individual needs. This alternative to a one-size-fits-all approach can address varying barriers to taking medications. The project will be a collaboration between Imperial College London and Hammersmith and Fulham Partnership (a GP Partnership of 5 GP practices), building on existing research from this team. The first stage of the PhD will investigate determinants of adherence across patient groups and individuals, using a variety of methods, all based on the Theoretical Domains Framework: a comprehensive framework of behavioural predictors. Secondary analysis of our ongoing survey on psychological determinants of statin adherence will test how these differ in different groups, e.g. those on many medications, those who have had a CVD event, ethnic minorities. An interview study will assess adherence determinants in adherent and non-adherent patients, and the patterns seen across individuals. This will be complemented by a systematic review of statin adherence determinants, and a review of statin adherence interventions, with intervention components categorised using the Behaviour Change Techniques Taxonomy. The student will map all these findings to identify adherence determinants across different groups, and corresponding techniques to address each adherence barrier. The second stage will design a tailored intervention to address the varying determinants, building on stage 1 findings. The intervention will be co-designed using workshops with diverse patients, clinicians, behavioural scientists and designers. The intervention will be scalable, and tailored to specific needs of each patient e.g. through a pathway of intervention components, based on patient characteristics and reported barriers. A pilot and feasibility study will assess whether recruitment is feasible, trial processes run smoothly, and the intervention is acceptable. The effect of the intervention on adherence will be examined, along with differences between patient groups. An interview and survey will investigate patient and clinician views on the intervention, and potential improvements. The PhD findings will inform a subsequent full trial of the intervention.