Advantages of concurrent preparation and reporting of systematic reviews of quantitative and qualitative evidence

Two systematic reviews played a key role in bringing together different types of evidence to inform policy decisions. The first was a review of process evaluations and controlled trials of young people promoting healthy behaviour to their peers.1 The second synthesised qualitative studies of children’s views of healthy eating and integrated the findings with a meta-analysis of controlled trials of healthy eating interventions.2 These systematic reviews were conducted against a backdrop of arguments about the value of different ways of knowing. Ann Oakley’s historical analysis of social science methods, their advocates and detractors, revealed power struggles between the alternatives of qualitative and quantitative social science.3 When quantitative and experimental methods were considered particularly influential, they were also seen by some qualitative researchers as inappropriate for investigating the social domain. Conversely, some adherents of quantitative or experimental methods saw qualitative methods as inadequate for informing policy or practice decisions. Competition and debate between the different standpoints was sometimes fierce, even abusive, and often unconstructive. The growth of systematic reviews, which initially addressed only questions about intervention effects, attracted critics who argued against whole bodies of literature, not just single studies.