BMJ  2008;336:1281-1283 (7 June), doi:10.1136/bmj.39569.510521.AD

Analysis

Complex interventions or complex systems? Implications for health economic evaluation

¹ Population Health Intervention Research Centre, University of Calgary, Calgary T2N 4N1, Canada , ² Health Economics Unit, School of Health and Social Development, Deakin University, Melbourne, Australia

Although guidelines exist for evaluating complex interventions, they may be of little help in dealing with the multiple effects of interventions in complex systems such as hospitals. Alan Shiell, Penelope Hawe, and Lisa Gold explain why it is important to distinguish the two types of complexity

Health researchers commonly use the notion of complexity to indicate the problems faced in evaluating the effectiveness of many non-drug interventions.^{1 2 3} However, although it is rarely delineated, complexity has two meanings. In the first it is a property of the intervention, and in the second it is a property of the system in which the intervention is implemented. We examine the implications of these two views for economic evaluation.

The first view of complexity, in effect, means complicated. This is the meaning used in the Medical Research Council’s framework for the evaluation of complex interventions.^{4 5} A complex intervention is "built up from a number of components, which may act both independently and inter-dependently."⁴ This makes it hard to define the "active ingredients" and to be sure which component or combinations of components is more important.

The second view makes reference to the insights offered by complexity science.^{6 7 8 9} Complexity is a . . . [Full text of this article]

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