Cognitive control and schizophrenia: The greatest reliability of the Stroop task

• Patients with the paranoid subtype of schizophrenia during the stabilization phase displayed impaired cognitive inhibition.
• Impairment of the three functions of cognitive inhibition in patients with the paranoid subtype of schizophrenia during the stabilization phase.
• A greatest reliability of all facets of cognitive inhibition with the Stoop interference index.

Three components of cognitive inhibition were compared in patients with schizophrenia and healthy controls. Nineteen patients with schizophrenia were compared to 30 healthy controls, matched for age, sex, and educational level. Cognitive inhibition was examined by (i) access to relevant information (Reading with distraction task), (ii) suppression of no longer relevant information (Trail Making Test B), and (iii) restraint of cognitive resources to relevant information (Stroop Test, Hayling Sentence Completion Test, Go/No-Go Test). Beck Depression Inventory, and Positive and Negative Syndrome Scale were also used. Compared to healthy controls, patients with schizophrenia and stabilized for at least 6 months were slower in the inhibition condition at the Stroop task, read more distractors at the RWD, and made more perseverative errors at the TMT, even after controlling for age, Mini-Mental State Examination score, information speed processing, and accuracy. This difference remained significant after taking into account the level of depressive symptoms and the severity of psychotic symptoms. In multivariate analyses, only the Stroop interference index explained cognitive inhibition deficit in patients with schizophrenia. The abnormal cognitive inhibition process observed in patients with schizophrenia could therefore concerns the ability to restraint, rather than the access or the suppression processes.