Some 40 years ago, the hypothesis was put forward that ordinary aspects of family life are crucial to an understanding of how families interact with those among them who have mental illnesses (Brown, 1985). The concept and measurement of the ‘expressed emotion’ (EE) within families were developed in the 1960s, initially for use in schizophrenia. They were subsequently used for a number of physical and psychiatric conditions, ranging from dementia to diabetes and Parkinson's disease. They have been a major impetus for the development and evaluation of social treatments of schizophrenia (Kuipers & Bebbington, 1990). The family's EE has been shown to be predictive of outcome in mental and physical illnesses in a variety of cultural settings.

Family environment is crucial both in the development of the individual and in creating and sustaining psychopathology in vulnerable individuals. There are studies which look at a socialisation paradigm, explaining how parental negativity can undermine children's learning about emotions and their management (Hoffman, 1983). Thus, the child may grow up without really understanding the implicit and explicit messages carried in the way the emotions are expressed. Externalising behaviours may be strongly influenced by family interactions that reinforce escalating negative affect and aggression (Beauchaine et al, 2007). One example of this has been in the field of self-harm, where the quality of communication and social problem-solving in the families has been studied (Tulloch et al, 1997; Speckens & Hawton, 2005; Nock & Mendes, 2008).