A neuropsychological comparison of obsessive-compulsive disorder and trichotillomania.
BACKGROUND
Obsessive-compulsive disorder (OCD) and trichotillomania (compulsive hair-pulling) share overlapping co-morbidity, familial transmission, and phenomenology. However, the extent to which these disorders share a common cognitive phenotype has yet to be elucidated using patients without confounding co-morbidities.


OBJECTIVE
To compare neurocognitive functioning in co-morbidity-free patients with OCD and trichotillomania, focusing on domains of learning and memory, executive function, affective processing, reflection-impulsivity and decision-making.


METHODS
Twenty patients with OCD, 20 patients with trichotillomania, and 20 matched controls undertook neuropsychological assessment after meeting stringent inclusion criteria.


RESULTS
Groups were matched for age, education, verbal IQ, and gender. The OCD and trichotillomania groups were impaired on spatial working memory. Only OCD patients showed additional impairments on executive planning and visual pattern recognition memory, and missed more responses to sad target words than other groups on an affective go/no-go task. Furthermore, OCD patients failed to modulate their behaviour between conditions on the reflection-impulsivity test, suggestive of cognitive inflexibility. Both clinical groups showed intact decision-making and probabilistic reversal learning.


CONCLUSIONS
OCD and trichotillomania shared overlapping spatial working memory problems, but neuropsychological dysfunction in OCD spanned additional domains that were intact in trichotillomania. Findings are discussed in relation to likely fronto-striatal neural substrates and future research directions.
Chamberlain
Samuel R
SR
Department of Psychiatry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK. src33@cam.ac.uk
Fineberg
Naomi A
NA
Blackwell
Andrew D
AD
Clark
Luke
L
Robbins
Trevor W
TW
Sahakian
Barbara J
BJ
D000328:Adult; D000339:Affect; D001288:Attention; D003072:Cognition Disorders / Q000175:diagnosis* / Q000523:psychology; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D007175:Impulsive Behavior / Q000175:diagnosis / Q000523:psychology; D007266:Inhibition, Psychological; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D009483:Neuropsychological Tests; D009771:Obsessive-Compulsive Disorder / Q000175:diagnosis* / Q000523:psychology; D009949:Orientation; D010364:Pattern Recognition, Visual; D011340:Problem Solving; D011597:Psychomotor Performance; D011930:Reaction Time; D012660:Semantics; D013223:Statistics as Topic; D014256:Trichotillomania / Q000175:diagnosis* / Q000523:psychology; D014706:Verbal Learning