Abstract
BACKGROUND: Diagnosis of trichotillomania (TTM) requires meeting several criteria that aim to embody the core pathology of the disorder. These criteria are traditionally interpreted monothetically, in that they are all equally necessary for diagnosis. Alternatively, a dimensional conceptualization of psychopathology allows for examination of the relatedness of each criterion to the TTM latent continuum. OBJECTIVES: First, to examine the ability of recently removed criteria (B and C) to identify the latent dimensions of TTM psychopathology, such that they discriminate between individuals with low and high degrees of hair pulling severity. Second, to determine the impact of removing criteria B and C on the information content of remaining diagnostic criteria. Third, to determine the psychometric properties of remaining TTM diagnostic criteria that remain largely unchanged in DSM-5; that is, whether they measure distinct or overlapping levels of TTM psychopathology. Fourth, to determine whether information content derived from diagnostic criteria aid in the prediction of disease trajectory (i.e., can relapse propensity be predicted from criteria endorsement patterns). METHOD: Statistics derived from item response theory were used to examine diagnostic criteria endorsement in 91 adults with TTM who underwent psychotherapy. RESULTS: The removal of two criteria in DSM-5 and psychometric validity of remaining criteria was supported. Additionally, individual trait parameters were used to predict treatment progress, uncovering predictive power where none previously existed. CONCLUSIONS: Diagnostic criteria for TTM should be examined in dimensional models, which allow for nuanced and sensitive measurement of core symptomology in treatment contexts.