What constitutes an ‘evidence-base’ in the healthcare communication field?

In the world of clinical practice and basic sciences, evidence has been clearly defined, with the greatest value given to randomized and other controlled trials and systematic reviews (meta-analyses of randomised controlled trials), followed by other critically appraised syntheses and synopses, and then individual controlled trials [1], [2]. This hierarchy is appropriate in many fields and has served scientists, clinicians, and policymakers well in making important decisions about treatments and informing further scientific work. In the healthcare communication field however, questions (including research questions) are varied, and often best answered by studies and information gathered through approaches other than trial-based studies.