Identifying standardized definitions of treatment response in trichotillomania: A meta-analysis

Symptom severity in trichotillomania clinical trials is typically rated using the Massachusetts General Hospital Hair Pulling Scale (MGH-HPS) and the National Institute of Mental Health Trichotillomania Severity Scale (NIMH-TSS). There are no universal definitions of treatment response on these scales. The absence of empirically supported definitions of treatment response hampers advances in trichotillomania treatment.

PubMed and CENTRAL databases were searched for trichotillomania clinical trials. A total of 14 studies were identified and 7 provided adequate data to be included in the meta-analysis (n = 270). Meta-DiSc software was employed. The Youden index and distance to corner were used to determine the optimal cut-point. Response was defined by the Clinical Global Impressions Improvement scale score ≤ 2.

The optimal cut-points for identifying response on the MGH-HPS was a 35% percent reduction [Youden Index 0.48; distance to corner 0.37] or a seven-point reduction [Youden Index 0.43; distance to corner 0.40]. The optimal cut-points for the NIMH-TSS was a 50% reduction [Youden Index 0.57; distance to corner 0.34] or a six-point reduction [Youden Index 0.53; distance to corner 0.36]. The optimal cut-points were similar when the analysis was confined to only trichotillomania trials involving adult subjects, but the scales appeared to have improved ability to define treatment response when pediatric subjects were excluded.

This study provides empirically determined cut-points of treatment response on the MGH-HPS and NIMH-TSS. These data-driven cut-points will benefit future research in trichotillomania by providing definitions of treatment response that can be defined a priori in clinical trials.