The use of theory in research.

All researchers should consider the theoretical basis for their studies very early on in the planning stage. The aim of this paper is to describe and discuss how theory (a 'comprehensive explanation of some aspect of nature that is supported by a body of evidence') can inform and improve the quality and relevance of pharmacy-based research. Theories can be applied at many stages of quantitative and qualitative (and mixed) research processes, including: providing rationale for the study; defining the aim and research questions; considering the methodological stance; developing data collection and generation tools; providing a framework for data analysis, and interpretation. The focus of the paper is on the use of theoretical lenses, their selection and application. Two key theoretical lenses and their potential applications are described: the Theoretical Domains Framework in studies of behavioural change, and Normalization Process Theory in implementing, embedding and integrating interventions.