Neuroimaging studies suggest involvement of frontal, striatal, limbic and cerebellar regions in trichotillomania, an obsessive-compulsive related disorder. However, findings regarding the underlying neural circuitry remains limited and inconsistent. Graph theoretical analysis offers a way to identify structural brain networks in trichotillomania. T1-weighted MRI scans were acquired in adult females with trichotillomania (n = 23) and healthy controls (n = 16). Graph theoretical analysis was used to investigate structural networks as derived from cortical thickness and volumetric FreeSurfer output. Hubs, brain regions with highest connectivity in the global network, were identified, and group differences were determined. Regions with highest connectivity on a regional level were also determined. There were no differences in small-worldness or other network measures between groups. Hubs in the global network of trichotillomania patients included temporal, parietal, and occipital regions (at 2SD above mean network connectivity), as well as frontal and striatal regions (at 1SD above mean network connectivity). In contrast, in healthy controls hubs at 2SD represented different frontal, parietal and temporal regions, while at 1SD hubs were widespread. The inferior temporal gyrus, involved in object recognition as part of the ventral visual pathway, had significantly higher connectivity on a global and regional level in trichotillomania. The study included women only and sample size was limited. This study adds to the trichotillomania literature on structural brain network connectivity. Our study findings are consistent with previous studies that have implicated somatosensory, sensorimotor and frontal-striatal circuitry in trichotillomania, and partially overlap with structural connectivity findings in obsessive-compulsive disorder.

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.

Trichotillomania is a prevalent but often hidden psychiatric condition, characterized by repetitive hair pulling. The aim of this study was to confirm or refute structural brain abnormalities in trichotillomania by pooling all available global data. De-identified MRI scans were pooled by contacting authors of previous studies. Cortical thickness and sub-cortical volumes were compared between patients and controls. Patients (n = 76) and controls (n = 41) were well-matched in terms of demographic characteristics. Trichotillomania patients showed excess cortical thickness in a cluster maximal at right inferior frontal gyrus, unrelated to symptom severity. No significant sub-cortical volume differences were detected in the regions of interest. Morphometric changes in the right inferior frontal gyrus appear to play a central role in the pathophysiology of trichotillomania, and to be trait in nature. The findings are distinct from other impulsive-compulsive disorders (OCD, ADHD, gambling disorder), which have typically been associated with reduced, rather than increased, cortical thickness. Future work should examine sub-cortical and cerebellar morphology using analytic approaches designed for this purpose, and should also characterize grey matter densities/volumes.

Disorders such as Trichotillomania (TTM) and skin-picking disorder (SPD) are associated with reduced flexibility and increased internally focused attention. While the basal ganglia have been hypothesized to play a key role, the mechanisms underlying learning and flexible accommodation of new information is unclear. Using a Bayesian Learning Model, we evaluated the neural basis of learning and accommodation in individuals with TTM and/or SPD. Participants were 127 individuals with TTM and/or SPD (TTM/SPD) recruited from three sites (age 18-57, 84% female) and 26 healthy controls (HC). During fMRI, participants completed a shape-button associative learning and reversal fMRI task. Above-threshold clusters were identified where the Initial Learning-Reversals BOLD activation contrast differed significantly (p < .05 FDR-corrected) between the two groups. A priori, effects were anticipated in predefined ROIs in bilateral basal ganglia, with exploratory analyses in the hippocampus, dorsolateral prefrontal cortex (dlPFC), and dorsal anterior cingulate cortex (dACC). Relative to HC, individuals with TTM/SPD demonstrated reduced activation during initial learning compared to reversal learning in the right basal ganglia. Similarly, individuals with TTM/SPD demonstrated reduced activation during initial learning compared to reversal learning in several clusters in the dlPFC and dACC compared to HC. Individuals with TTM/SPD may form or reform visual stimulus-motor response associations through different brain mechanisms than healthy controls. The former exhibit altered activation within the basal ganglia, dlPFC, and dACC during an associative learning task compared to controls, reflecting reduced frontal-subcortical activation during initial learning. Future work should determine whether these neural deficits may be restored with targeted treatment.

Trichotillomania (TTM) and skin picking disorder (SPD) are common and often debilitating mental health conditions, grouped under the umbrella term of body-focused repetitive behaviors (BFRBs). Recent clinical subtyping found that there were three distinct subtypes of TTM and two of SPD. Whether these clinical subtypes map on to any unique neurobiological underpinnings, however, remains unknown.

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.

Background: Trichotillomania (TTM) has been associated with childhood trauma and perceived stress. While it has been hypothesized that hair-pulling regulate negative emotions, the relationship between childhood trauma, perceived stress, emotion regulation, and hair-pulling has not been well-studied. Methods: Fifty-six adults with TTM and 31 healthy controls completed the Childhood Trauma Questionnaire (CTQ), Perceived Stress Scale (PSS), and Difficulties in Emotion Regulation Scale (DERS). Hair-pulling severity was measured with the Massachusetts General Hospital-Hair Pulling Scale. CTQ, PSS, and DERS total scores were compared across groups using ANCOVA and the correlation between hair-pulling severity and emotion dysregulation was determined. Regression analyses were used to estimate the association of CTQ and PSS totals with DERS, and to determine whether associations between predictors and dependent variable (DERS) differed across groups. Results: TTM patients reported higher rates of childhood trauma (p <= 0.01), perceived stress (p = 0.03), and emotion dysregulation (p <= 0.01). There was no association between emotion dysregulation and pulling severity (r = -0.02, p = 0.89). Perceived stress was associated with emotion dysregulation in both groups (p < 0.01), and no association between childhood trauma and emotion dysregulation in either group. Perceived stress was the only significant predictor of emotion dysregulation in both groups (F = 28.29, p < 0.01). Conclusion: The association between perceived stress and emotion dysregulation is not specific to TTM, and there is no association between emotion dysregulation and hair-pulling severity, suggesting that key factors other than emotion dysregulation contribute to hair-pulling. Alternative explanatory models are needed.

Although pathological skin-picking has been documented in the medical literature since the 19th century, it has only recently been included as a distinct entity in psychiatric classification systems. In the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition and the proposed International Classification of Diseases, Eleventh Revision, excoriation (skin-picking) disorder (ED), also known as neurotic excoriation, psychogenic excoriation, or dermatillomania), is described as recurrent picking of skin, leading to skin lesions and significant distress or functional impairment. ED is listed as one of the obsessive-compulsive and related disorders, given its overlap with conditions such as trichotillomania (hair-pulling disorder). Arguably, its inclusion and delineation in the diagnostic nomenclature will lead to increased awareness of the condition, more research, and ultimately in treatment advances. This systematic review aims to provide readers with an up-to-date view of current treatment options for ED. A MEDLINE search of the ED treatment literature was conducted to collate relevant articles published between 1996 and 2017. The findings indicate that a number of randomized controlled trails on ED have now been published, and that current management options include behavioral therapy (habit reversal or acceptance-enhanced behavior therapy), and medication (selective serotonin reuptake inhibitors or N-acetyl cysteine).