title: Motor inhibition and cognitive flexibility in obsessive-compulsive disorder and trichotillomania.
abstract: OBJECTIVE
  Problems with inhibiting certain pathological behaviors are integral to obsessive-compulsive disorder (OCD), trichotillomania, and other putative obsessive-compulsive spectrum disorders. The authors assessed and compared motor inhibition and cognitive flexibility in OCD and trichotillomania for the first time, to their knowledge.
  
  
  METHODS
  The Stop-Signal Task and the Intradimensiona/Extradimensional Shift Task were administered to 20 patients with OCD, 17 patients with trichotillomania, and 20 healthy comparison subjects.
  
  
  RESULTS
  Both OCD and trichotillomania showed impaired inhibition of motor responses. For trichotillomania, the deficit was worse than for OCD, and the degree of the deficit correlated significantly with symptom severity. Only patients with OCD showed deficits in cognitive flexibility.
  
  
  CONCLUSIONS
  Impaired inhibition of motor responses (impulsivity) was found in OCD and trichotillomania, whereas cognitive inflexibility (thought to contribute to compulsivity) was limited to OCD. This assessment will advance the characterization and classification of obsessive-compulsive spectrum disorders and aid the development of novel treatments.
authors.affiliation: Department of Psychiatry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Box 189, Cambridge, UK. src33@cam.ac.uk
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Chamberlain
authors.forename: Naomi A
authors.initials: NA
authors.lastname: Fineberg
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Blackwell
authors.forename: Trevor W
authors.initials: TW
authors.lastname: Robbins
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Sahakian
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D003072:Cognition Disorders / Q000175:diagnosis*; D003192:Compulsive Behavior / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis*; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D014256:Trichotillomania / Q000175:diagnosis*