Reliability and validity of the Trichotillomania Dimensional Scale (TTM-D)

Trichotillomania (TTM) is characterized by repetitive hair pulling resulting in hair loss. The Trichotillomania Dimensional Scale (TTM-D) is a newly developed DSM-5 scale that aims to assess the symptoms of TTM dimensionally. The aim of this current study was to examine the psychometric properties of the TTM-D in a sample of 483 participants. Principal Component Analysis indicated a single factor structure of the TTM-D. Internal consistency and test retest reliability was high (α = 0.89 and r = 0.91 respectively). The TTM-D demonstrated excellent convergent validity with the Massachusetts General Hospital Hair Pulling Scale (MGH-HPS; rs = 0.90) and divergent validity with the Depression Anxiety and Stress Scale (DASS-21; rs = 0.45). Further, the TTM-D demonstrated equivalence between online and pen-and-paper administrations (rs= 0.93). The findings suggest that the psychometric properties of TTM-D are sound and well supported within a community sample.