Comparison of cognitive deficits among drug-naive patients with schizophrenia and major depressive disorder

Background: Cognitive deficits have been well-established among patients with severe mental illness. The aim of this study was to clarify the patterns of cognitive deficits in drug-naive patients with schizophrenia and non-psychotic major depressive disorder (MDD) as compared with controls.

Methods: Thirty drug-naïve participants with schizophrenia, 30 counterparts with non-psychotic MDD, and 30 age-, sex-, and education years-matched healthy controls were recruited. Neuropsychological tests, including the Wisconsin Card Test (WCST), the Continuous Performance Test (CPT) and the Finger Tapping Test (FTT), were administered.

Results: Patients with schizophrenia performed more poorly than the patients with MDD and the normal controls in the WCST. The patients with schizophrenia and the patients with MDD both performed more poorly than the normal controls in the CPT. The patients with MDD also performed more poorly than the normal controls in the FTT.

Limitations: The age of onset of MDD in this study was younger than in previous reports. The cross-sectional design, small sample sizes, and limited numbers of neuropsychological domains in this study are all obstacles to making a clear causal conclusion.

Conclusions: These results revealed a distinct pattern of neurocognitive dysfunction among drug-naive patients with schizophrenia and MDD, which may imply different underlying neurobiological mechanisms in schizophrenia and MDD.