Comorbidity in trichotillomania (hair‐pulling disorder): A cluster analytical approach

Abstract Background A promising approach to reducing the phenotypic heterogeneity of psychiatric disorders involves the identification of homogeneous subtypes. Careful study of comorbidity in obsessive‐compulsive disorder (OCD) contributed to the identification of the DSM‐5 subtype of OCD with tics. Here we investigated one of the largest available cohorts of clinically diagnosed trichotillomania (TTM) to determine whether subtyping TTM based on comorbidity would help delineate clinically meaningful subgroups. Methods As part of an ongoing international collaboration, lifetime comorbidity data were collated from 304 adults with pathological hair‐pulling who fulfilled criteria for DSM‐IV‐TR or DSM‐5 TTM. Cluster analysis (Ward's method) based on comorbidities was undertaken. Results Three clusters were identified, namely Cluster 1: cases without any comorbidities (n = 63, 20.7%) labeled “simple TTM,” Cluster 2: cases with comorbid major depressive disorder only (N = 49, 16.12%) labeled “depressive TTM,” and Cluster 3: cases presenting with combinations of the investigated comorbidities (N = 192, 63.16%) labeled “complex TTM.” The clusters differed in terms of hair‐pulling severity (F = 3.75, p = .02; Kruskal–Wallis [KW] p