%0 Journal Article %T Towards a better understanding of the role of psychological variables in arthritis outcome research %A Annelies Boonen %J Arthritis Research & Therapy %D 2010 %I BioMed Central %R 10.1186/ar2922 %X We are disturbed not (only) by events, but (also) by the views which we take of them.(Epictetus, born 55 AD)Likely, the majority of rheumatologists have been trained in the belief that health outcomes are mainly explained by biomedical factors related to the disease. In the previous issue of Arthritis Research and Therapy, the biomedical model is challenged by the article of Brionez and coworkers [1]. The authors show that the total explained variation of the Bath Ankylosing Spondylitis Functional Index increased from 32% to 56% when adding various psychological variables (depression, coping and beliefs about controllability) to the demographic and clinical variables. Although the Bath Ankylosing Spondylitis Functional Index and other patient-reported outcome measures have been criticized by experts in ankylosing spondylitis because of their subjective nature, this paper helps to understand mechanisms underlying these effects and quantifies the magnitude of their influence.Psychology is the discipline that attempts to understand the role of mental functions in individual and social behavior. In medicine, psychology became more widely integrated when the biopsychosocial model of disease was adopted by the World Health Organization, through the approval of the International Classification of Functioning, Disability and Health (ICF) (Figure 1) as the framework and classification of health.In the biopsychosocial model, functioning and health results from a complex interplay of the health components - body functions and structures, activities and participation - and the contextual factors - environmental factors and personal factors [2]. In the ICF, psychological variables can be found either within the body functions or within the personal factors. Depression, as in the study by Brionez and coworkers [1], is part of the body functions (emotional function) - and as such can be the direct consequence of the health condition or an emotional reaction to the presence of the %U http://arthritis-research.com/content/12/1/106