Cognitive endophenotypes in OCD: A study of unaffected siblings of probands with familial OCD

Impairments in executive functions and non-verbal memory are considered potential endophenotype markers of obsessive–compulsive disorder (OCD). For the neuropsychological deficits to be considered endophenotypes, they should be demonstrable in unaffected family members. To compare the neuropsychological performance in unaffected siblings of probands with familial OCD with that of individually matched healthy controls. Twenty-five unaffected siblings of OCD probands with familial OCD, and 25 individually matched healthy controls were assessed with tests of attention, executive function, memory and intelligence. Unaffected siblings showed significant deficits in tests of decision making and behavioural reversal i.e., the Iowa Gambling Task (IGT) and the Delayed Alternation Test (DAT) respectively, but performed adequately in other tests. Our study suggests that the deficits in decision making and behavioural reversal could be potential endophenotypes in OCD. These deficits are consistent with the proposed neurobiological model of OCD involving the orbitofrontal cortex. Future studies could couple cognitive and imaging strategies to identify neurocognitive endophenotypes in homogenous samples of OCD.