Trichotillomania is a relatively common illness whose neurobiology is poorly understood. One treatment for adult trichotillomania, n-acetyl cysteine (NAC), has antioxidative properties, as well as effects on central glutamatergic transmission. Preclinical models suggest that excessive oxidative stress may be involved in its pathophysiology.

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.

Prior work suggested that trichotillomania may have four subtypes based on the extent to which pulling is automatic or focused in nature. 238 adults with trichotillomania undertook clinical and cognitive assessments and were assigned into four subtypes based on k-means clustering of Milwaukee Inventory for Subtypes of Trichotillomania-Adult Version (MIST-A) scores. We examined whether a cluster solution was apparent using conventional metrics. Based on prior literature, we then force-fitted a four subtype model (low-low, low-high, high-low, high-high). Subtypes were compared and validity of the MIST-A subtyping approach was evaluated. A cluster solution did not converge based on conventional metrics. Following force-fitting, subtypes did not differ on demographic variables, age at symptom onset, nor duration of illness. The high-focused high-automatic subtype had worse symptom severity than other subtypes. Co-morbid depression was more common in the low-focused low-automatic and high-focused low-automatic subtypes. This study suggests that MIST-A subtypes may not be valid or clinically useful based on several issues. First, k-means models indicated that the MIST-A data did not generate any cluster solutions. Second, when a forced cluster solution was fitted, the subtypes did not differ on the vast majority of measures. Third, force-fitting four subtypes yielded findings that were logically inconsistent (e.g. worse quality of life in one group, but higher rates of comorbid anxiety/depression in others). Overall, we suggest that both focused and automatic pulling may characterize the same pulling episode, or certainly the same person across episodes. Thus they may be clinically relevant variables, but not forming coherent subtypes.

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.

Despite being discussed in the psychiatric literature for decades, very little is known about personality features associated with trichotillomania and skin picking disorder (known as body focused repetitive behavior disorders, BFRBs); and the contribution of personality traits to their clinical presentations.

Trichotillomania (TTM) is characterized by recurrent hair pulling and associated hair loss. Skin picking disorder (SPD) is characterized by recurrent skin picking and associated scarring or tissue damage. Both disorders are also accompanied by psychological distress and poor sleep. Very little, however, is known about lifestyle variables that may contribute to symptom severity in these disorders.

Body-focused repetitive behaviors (BFRBs), such as trichotillomania and skin picking disorder, are psychiatric disorders characterized by repetitive grooming that result in hair loss or excoriations. Questions remain as to whether there are racial/ethnic differences in the clinical presentation of BFRBs.

Trichotillomania (TTM) and skin picking disorder (SPD) have been characterized as body-focused repetitive behaviors (BFRBs) and have been grouped in the DSM-5 as part of the obsessive-compulsive and related disorders. Despite the clinical similarities between BFRBs and the compulsions of OCD, there has been little research regarding the degree to which compulsivity underpins these behaviors. 88 adults (69 female; mean age 30.9 years) with DSM-5 TTM or SPD completed standard diagnostic interviews, basic demographic information, symptom inventories about TTM and SPD, and measures of disability/functioning. Compulsivity was measured using the 15-item Cambridge-Chicago Compulsivity Trait Scale (CHI-T). Relationships between CHI-T scores and the other measures of interest were characterized using Pearson's correlations. Of the 88 participants, 48 (54.5%) had TTM, 37 (42.0%) had SPD and 3 (3.4%) had both. CHI-T total scores correlated with worse disability and quality of life but not with BFRB symptom severity. This study demonstrates that compulsivity is a marked contributor to worse disability and quality of life in people with BFRBs, more so than conventional measures of BFRB symptom severity (which did not correlate with disability/quality of life). Future work should include compulsivity measures in BFRB studies (including treatment trials) and explore its role in other related disorders.