Out of the box : moving from categories to dimensions in the phenomenology of depression and anxiety.

Research into the relation between psychopathology and etiological factors has not yet resulted in clear findings. One of the probable causes is that most researchers use the categorical DSM-IV Classification of mental disorders. A dimensional system has several advantages compared to categorical systems: comorbidity, lack of diagnostic agreement and arbitrary nature of used boundaries are no longer a problem. Our aim was to develop a model with dimensions that can adequately describe patients with mood- and anxiety disorders. This project used data collected through Routine Outcome Monitoring (ROM), a monitoring system for patient care. First, we validated a Dutch adaptation of an instrument based on the tripartite model. Next, we formulated an extension of this model with 5 dimensions. Consequently we presented a second model with 6 dimensions: feelings of worthlessness, fatigue, somatic arousal, anxious apprehension, phobic fear and tension. We used several analysis techniques to create a valid and reliable dimensional model. Each individual factor and the total of factors can be regarded as unidimensional measurement scales. This model can describe the clinical state of patients more specifically than the tripartite model, and can be used in subsequent research into etiological factors of psychopathology (e.g. endophenotype, genotype, trauma's, personality)