Cognitive inhibition in trichotillomania and obsessive-compulsive disorder.

Cognitive inhibition was investigated in 21 trichotillomania (TTM), 21 obsessive-compulsive disorder (OCD) and 26 healthy control (HC) participants using a block cued directed forgetting task. After encoding a word list, participants were instructed to intentionally FORGET these words and to REMEMBER another word list. Both lists included TTM-related and neutral (kitchen-related) words in equal proportions, with the TTM-related words generally of negative valence and the kitchen-related words generally of neutral valence for all participants. A superior free recall of REMEMBER versus FORGET words suggests intact cognitive inhibition. The performance of OCD participants indicated a specific deficit in inhibiting the retrieval of information with negative valence, which was not found in TTM. HC participants, in contrast to TTM and OCD participants, were rather inattentive to negative information. In conclusion, although attention was disproportionately directed towards negative information in both disorders, cognitive inhibition deficits appeared specific to OCD.