What is a psychopathology dimension?

Coherence in the science and practice of mental health assessment depends upon a tight connection between psychopathology concepts that are used and the way those concepts are operationalized and defined. In contrast, the use of the same word to mean more than one thing contributes to incoherence, inefficiency, and confusion. In this paper, we review three possible meanings of the word "dimension" as it relates to the assessment of psychopathology and describe how the indiscriminate use of this word has caused confusion in the general context of the transition to a more evidence-based approach to mental health diagnosis. We attempt to disambiguate the term "dimension" by demarcating three concepts that can be distinguished based on different empirical standards: continuous variables, unidimensional dimensions, and distinct dimensions.