Complexity entails methodological challenges in assessing health care interventions. In order to address these challenges, a series of characteristics of complexity have been identified in the Health Technology Assessment (HTA) literature. These characteristics are primarily identified and developed to facilitate effectiveness, safety, and cost-effectiveness analysis. However, ethics is also a constitutive part of HTA, and it is not given that the conceptions of complexity that appears relevant for effectiveness, safety, and cost-effectiveness analysis are also relevant and directly applicable for ethical analysis in HTA. The objective of this article is therefore to identify and elaborate a set of key characteristics of complex health care interventions relevant for addressing ethical aspects in HTA. We start by investigating the relevance of the characteristics of complex interventions, as defined in the HTA literature. Most aspects of complexity found to be important when assessing effectiveness, safety, and efficiency turn out also to be relevant when assessing ethical issues of a given health technology. However, the importance and relevance of the complexity characteristics may differ when addressing ethical issues rather than effectiveness. Moreover, the moral challenges of a health care intervention may themselves contribute to the complexity. After identifying and analysing existing conceptions of complexity, we synthesise a set of five key characteristics of complexity for addressing ethical aspects in HTA: 1) multiple and changing perspectives, 2) indeterminate phenomena, 3) uncertain causality, 4) unpredictable outcome, and 5) ethical complexity. This may serve as an analytic tool in addressing ethical issues in HTA of complex interventions.
Keywords: complex intervention; complex technology; ethical analysis; ethics; health technology; health technology assessment.