Seminar Series report: From complex interventions to complex systems: implications for evaluation

News article 10 Jul 2015

LSTM’s Seminar Series continued with a talk by Mark Petticrew, Professor of Public Health Evaluation at the London School of Hygiene and Tropical Medicine. His talk, entitled ‘from complex interventions to complex systems: implications for evaluation’ was introduced by LSTM’s Professor Paul Garner.  He began his talk by discussing the reasons behind the current interest in complex interventions (poor health, health inequalities, and complex remedies).

As an expert in complexity, and having helped develop trials in this area and helped form guidelines in how to describe complexity, the audience was a bit taken aback when he suggested that there is “no such thing as simple” and the key question was whether understanding complexity would actually add anything useful. Systematic reviews can help examine different interventions in different systems and different points in time to see whether they work and if this changes over time.

Mark described the “commercial determinants of health” showing how complexity was used by tobacco companies to rubbish the link between smoking and cancer, and by the alcohol industry to obfuscate proposals to increase prices to reduce consumption. He wondered whether at times academics too hide behind complexity.

Prof Petticrew disputed the common viewpoint of “What Works for Whom, and under What Circumstances,” by suggesting that everything will work for someone in some circumstances.  He continued by saying we need to strike a difficult balance between narrow hypothesis testing and post-hoc dredging for findings. Furthermore that systematic reviews are not about finding things that work, but finding a range of positive and negative effect

In conclusion, he suggested we need to be aware of making complex problems insoluble for policy makers and beware of demanding perfect solutions to complex problems. When evaluating change we need to identify system boundaries, consider what part of the system is valuable, and what process in the system are valuable. At the end of the talk, Mark directed the audience towards his MRC-funded Mach (Meta-analysis, Complexity and Heterogeneity) Project website (