Evidence in the development of health policy.

For over a century and a half, reformers, researchers and politicians have complained that social and public health policy is not based on evidence. Linear models of knowledge transfer gaps are consistently shown to be poor predictors of research uptake. Public health research, in particular, involves more elements than the linear biomedical model of translation into healthcare products or interventions. Policy makers certainly need to be more sophisticated in understanding and commissioning different types of research and acting on it. However, researchers also need to be much more sophisticated and less naive in understanding how research does and does not influence policy, and how to go about helping policy makers to interpret the jigsaw of evidence, and its relevance and usability.