Principles for being theoretical-Increasing the impact of research conducted in primary care.

Primary care is a unique research environment and is difficult to study well without disrupting the delivery of care. Recent developments in implementation and care delivery sciences have facilitated real world tests of interventions. However primary care research often misses a foundational component of quality - "being theoretical." Using cancer prevention and control as an example, this commentary advocates for the imperative of using theory to guide research and describes three principles for being theoretical. These principles, readily amenable to clinical settings, will produce studies that do more than answer "did it work?" and therefore increase the impact of primary care-based research across the cancer continuum.