Professor Ruth Jepson is a professor of public health in social science and Director of the Scottish Collaboration for Public Health Research and Policy at the University of Edinburgh. She has a background in nursing and has worked in the field of public health for over 30 years. Her expertise includes systematic reviews, co-production, qualitative methods and the development and evaluation of complex public health interventions.  She was part of the team who developed the Six Steps in Quality Intervention Development and has used it widely in her teaching and research.Dr John McAteer BSc Msc PhD is a Chartered Psychologist and Associate Fellow of the British Psychological Society.  John’s expertise is in behaviour change, public health, and the development and evaluation of complex interventions.  Over the past 18 years, John has led and been involved with many intervention projects, working closely with policy makers and practitioners.  His work has fed into national policy initiatives such as the Scottish Government’s National Parenting Strategy.   He is currently a co-Director of Grow Public Health Research and Consultancy, in Edinburgh, UK.   Dr Andrew James Williams MPH PhD FHEA is Senior Lecturer in Public Health at the University of St Andrews, UK. Andrew has been involved with the evaluation of nation-wide (abolition of prescription fees) and city-wide policies (20mph speed limits) through to smaller scale youth work and community development interventions. Having trained in quantitative methods (epidemiology), Andrew’s interests are now in what sustains and improves our health, which means grappling with the complex systems that influence health. He is particularly keen that we learn from all interventions through thorough evaluation.Dr Lawrence Doi BSc MPH PhD FHEA is a Lecturer in Applied Public Health and Postgraduate Research Director (Nursing Studies) at the University of Edinburgh, UK. His expertise is in developing and evaluating complex interventions. Lawrence taught on developing and evaluating complex intervention course at masters level for five years. He has been involved in several intervention development projects, including leading a team of researchers and stakeholders to develop an intervention to reduce high readmission rates for patients following intensive care admission. He is currently the lead researcher on a Scottish Government funded project evaluating the universal health visiting pathway. Dr Audrey Buelo MPH PhD is an epidemiologist studying the COVID-19 vaccination response at Public Health Scotland. She received her Doctorate in Applied Health and Social Sciences at the University of Edinburgh. Her doctorate research involved the development of a physical activity and mental health improvement intervention for women who are at high risk of Type 2 diabetes through novel methods of co-production.

• Introduction to the BookPrinciples of Intervention DevelopmentCausality, Systems and Complexity6SQuID Step 1: Understand the Problem and Its CausesStep 2: Identifying Modifiable Causal FactorsStep 3: Identifying How to Bring About Change: Theory of ChangeStep 4: Identifying How to Deliver Change Mechanisms – Theory of ActionStep 5 of 6squid: Testing and Adapting the Intervention6SQuID Step 6: Collecting Sufficient Evidence of Effectiveness to Proceed to a Rigorous EvaluationCase StudiesConclusion