Introduction: Assessment in Health Psychology: Introduction

As early as the beginning of the 1980s, it was pointed out that effective measurement and assessment are a sine qua non for the advancement of health psychology and the development of rigorous and successful theories and applications (Karoly, 1985; Keefe & Blumenthal, 1982). Properly developed, reliable, and well-validated assessment instruments and sound measure- ment procedures are needed for (a) the assessment of health status and the consequences of illness on quality of life and functioning; (b) the examination of the type and the strength of the association between well-being and other variables, including stress, health behaviours, and personal and social characteristics; and the assessment of the ability of a theoretical model or a construct to explain and predict health- and illness-related reactions, as well as the evaluation of the effectiveness of an intervention programme. Although frequently ignored, assessment and advancement in assessment lie at the heart of the scientific knowledge developed in each discipline, including health psychology, and of its contribution to human welfare.