Abstract
Trichotillomania (hair-pulling disorder) is characterized by the repetitive pulling out of one's own hair, and is classified as an Obsessive-Compulsive Related Disorder. Abnormalities of the ventral and dorsal striatum have been implicated in disease models of trichotillomania, based on translational research, but direct evidence is lacking. The aim of this study was to elucidate subcortical morphometric abnormalities, including localized curvature changes, in trichotillomania. De-identified MRI scans were pooled by contacting authors of previous peer-reviewed studies that examined brain structure in adult patients with trichotillomania, following an extensive literature search. Group differences on subcortical volumes of interest were explored (t-tests) and localized differences in subcortical structure morphology were quantified using permutation testing. The pooled sample comprised N = 68 individuals with trichotillomania and N = 41 healthy controls. Groups were well-matched in terms of age, gender, and educational levels. Significant volumetric reductions were found in trichotillomania patients versus controls in right amygdala and left putamen. Localized shape deformities were found in bilateral nucleus accumbens, bilateral amygdala, right caudate and right putamen. Structural abnormalities of subcortical regions involved in affect regulation, inhibitory control, and habit generation, play a key role in the pathophysiology of trichotillomania. Trichotillomania may constitute a useful model through which to better understand other compulsive symptoms. These findings may account for why certain medications appear effective for trichotillomania, namely those modulating subcortical dopamine and glutamatergic function. Future work should study the state versus trait nature of these changes, and the impact of treatment.
Highlights
Trichotillomania, known as hair-pulling disorder, is characterized by the repetitive pulling out of one's own hair, leading to significant functional impairment (APA, 2013)
Healthy volunteer studies support a role for dopamine D2 receptors in the putamen in regulating response inhibition (Ghahremani et al, 2012), which may in turn support a role for dorsal striatum dopamine receptors in the pathophysiology of trichotillomania, with potential treatment implications
In addition to macroscopic volume changes in the left putamen, we found here that the right amygdala was abnormally small in patients with trichotillomania compared to healthy controls
Summary
Trichotillomania, known as hair-pulling disorder, is characterized by the repetitive pulling out of one's own hair, leading to significant functional impairment (APA, 2013). Trichotillomania has peak age of onset in adolescence, is more common in women than in men, and is currently classified as an Obsessive-Compulsive Related Disorder (Grant and Chamberlain, 2016). In contrast to the repetitive compulsive acts observed in obsessive-compulsive disorder (OCD), repetitive behaviors in trichotillomania are not generally driven by intrusive thoughts. In view of the recent development of animal models with good validity (Chamberlain et al, 2007b; Greer and Capecchi, 2002; Hyman, 2007), trichotillomania constitutes a key model for better understanding compulsive symptoms more generally. Surprisingly little is known about the neurobiological basis of this disorder in humans (Christenson et al, 1993; Cohen et al, 1995; Mansueto et al, 2007; Odlaug and Grant, 2010)
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