Just one in 20 people worldwide have no health problems, with a third of the world's population (2·3 billion individuals) experiencing more than five ailments. A straightforward way to assess the health status of a population is to focus on mortality or life expectancy. A focus on mortality, however, does not take into account that the burden of diseases is not only that they kill people, but that they cause suffering to people who live with them. This course focuses on how psychological, behavioural, and cultural factors contribute to physical health and illness and examines the impact of health conditions on cognition and wellbeing. We also consider the impact of public policy and health inequalities.