The very high prevalence of lifetime mental disorders, close to 50%, indicates that mental disorders are not a rare abnormal condition but rather a common reaction of human beings. Major factors for developing a disorder should therefore be explored in the field of the interactions between the individuals with their genetic structures, their personal history and the environment.

The notion of stress refers to the impact of the environment on the subject and is likely to become a major etiopathogenic research area. Brian Leonard reviewed for us the dysregulation of the HPA axis by stress focusing on CRF and the vicious cycle induced by glucocorticoids receptors desensitization to the negative feedback of the HPA axis on their own structures. As a consequence of chronic stress Thakore reminds us the toxic influence of a chronic increase in glucocorticoids on the neuronal volume and the dendritic arborization. Such a reduction is observed in the hippocampal structures of schizophrenics as well as different cellular abnormalities (Weinberger [Reference Weinberger4], Lawrie et al. [Reference Lawrie, Whalley and Byrne2]). Functionally the hippocampal dependant impaired verbal memory is a predictor of outcome (Green [ 1 ]). However even in individuals previously well adapted living in the community, stress may strongly favor the development of mental disorders as shown by the study presented by Per Bech. These findings show the relevance of the concept of stress and the importance of investing resources into this research area.

A recent assessment of the frequency and burden of mental disorders in Europe is now available. Two figures produced by a multinational group of experts are striking:

• a) Mental disorders account for about 25% of the burden produced by all diseases (35% if neurological disorders are taken into account).

• b) About 50% of the population lifetime (or one-third within 1 year) experiences some mental disorder [Reference Wittchen, Jönsson and Olesen5].

The burden associated with mental disorders includes many facettes such as the cost for society (more than 300 Billion Euros, half for direct and half for indirect costs), the cost for the family and the cost for patients. This last cost is not just a statistical variable, e.g. depression will be the leading cause of all medical burdens in 2020 according to Murray and Lopez [Reference Murray and Lopez3], however for patients schizophrenia will be the most disabling and burdensome disorder. The impact of the disorder at the symptoms, the family, the social level and the consequences in terms of individual suffering are a complex but necessary approach. It gives an important insight into the consequences of the disease to the professionals and also to the health care policy makers. Quality-oflife (QOL) measurements take this complexity into account and J. Bobes accurately presents the underlying concepts, the structure and psychometric properties of the QOL instruments for one of the most difficult category of patients, those with Schizophrenia.