Psychological theories focus on the personal and the behavioural factors, which influence the development of health and disease. In this chapter, we will use two main approaches. First, learning theories focus on processes created by experience and lead to changes in behaviour. They emphasise the role of information processing and the role of self-efficacy for the development of health. Second, coping theories analyse the mechanisms and processes of dealing with health risks and burdens. They examine the relation between personality traits and the occurrence of health disorders and diseases and the subjective mechanisms of mastering stress.