Health and illness have causes beyond biology and behaviour. However, a systematic approach is still largely missing. To study the effect of health intervention, many interrelated factors (and the multi-scale and dynamic interplay between them) should be taken into account: from an individual’s genes, biology and behaviour, to the social and physical environment and medical care. This requires integration of knowledge, data, concepts and theories from many disciplines, ranging from biology and medical sciences to psychology, sociology and economics.