Repetitive negative thinking (e.g., rumination; RNT) is a transdiagnostic process of increasing interest in theoretical models of psychopathology and in empirical study. My research into RNT in complex psychiatric samples has been broadly based, including the study of measure psychometrics, potential mechanisms underlying RNT, and how RNT often mediates treatment outcomes. For example, although the Ruminative Responses Scale (RRS) has been suggested as a two-factor measure of rumination in student samples, factor analyses of the RRS in psychiatric samples have suggested other factor solutions.