Syndromes versus symptoms: towards validation of a dimensional approach of depression and anxiety

Abstract

There is a growing awareness that research of the etiology of depressive and anxiety disorders has been hampered by their strictly categorical definition in the Diagnostic and Statistical Manual (DSM). The DSM uses a syndrome approach, which __ although beneficial for standardization - has inherent problems that make it suboptimal for research: high rates of (artificial) comorbidity, diagnostic heterogeneity and the unrealistic assumption of discontinuity between ill and healthy. A dimensional approach that focusses on the relative severity of continuous symptom domains could be more optimal but measurement and the added value of such dimensions has been debated. Therefore, this dissertation was aimed to investigate (1) the internal validity and possibility to measure dimensions and (2) their added value in etiological and clinical research. The results showed that measurement of dimensions can be optimized using self-report questionnaires. In addition, dimensions were shown to have added value in etiological and clinical research. Because of their specific and continuous nature, dimensions could be used to uncover symptom-specific and/or non-linear association. Together, the results suggest that dimensions of depression and anxiety have internal and external validity and have the potential to improve the psychiatric research