Trichotillomania is characterized by repetitive pulling out of one's own hair. Impaired response inhibition has been identified in patients with trichotillomania, along with gray matter density changes in distributed neural regions including frontal cortex. The objective of this study was to evaluate impaired response inhibition and abnormal cortical morphology as candidate endophenotypes for the disorder. Subjects with trichotillomania (N=12), unaffected first-degree relatives of these patients (N=10), and healthy controls (N=14), completed the Stop Signal Task (SST), a measure of response inhibition, and structural magnetic resonance imaging scans. Group differences in SST performance and cortical thickness were explored using permutation testing. Groups differed significantly in response inhibition, with patients demonstrating impaired performance versus controls, and relatives occupying an intermediate position. Permutation cluster analysis revealed significant excesses of cortical thickness in patients and their relatives compared to controls, in right inferior/middle frontal gyri (Brodmann Area, BA 47 & 11), right lingual gyrus (BA 18), left superior temporal cortex (BA 21), and left precuneus (BA 7). No significant differences emerged between groups for striatum or cerebellar volumes. Impaired response inhibition and an excess of cortical thickness in neural regions germane to inhibitory control, and action monitoring, represent vulnerability markers for trichotillomania. Future work should explore genetic and environmental associations with these biological markers.
Bibliographical noteFunding Information:
This research was supported by a grant from the Trichotillomania Learning Center, USA, to Mr. Odlaug; and by a grant from the Academy of Medical Sciences, UK, to Dr. Chamberlain. Neither of these entities had any further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the paper for publication.
Mr. Odlaug received a research grant from the Trichotillomania Learning Center, consults for H. Lundbeck Pharmaceuticals, and has received royalties from Oxford University Press. Dr. Chamberlain consults for Cambridge Cognition. Mr. Leppink and Ms. Derbyshire report no financial or other conflicts of interest. Dr. Grant has received research grants from National Institute of Mental Health (RC1 DA028279-01) , National Center for Responsible Gaming, Forest, and Roche Pharmaceuticals. Dr. Grant receives yearly compensation from Springer Publishing for acting as Editor-in-Chief of the Journal of Gambling Studies and has received royalties from Oxford University Press, American Psychiatric Publishing, Inc., Norton Press, and McGraw Hill.
This research was supported by a grant from the Trichotillomania Learning Center , USA, to Mr. Odlaug and by a grant from the Academy of Medical Sciences , UK, to Dr. Chamberlain.
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