Time of day of testing and neuropsychological performance of schizophrenic patients and healthy controls.

The current project examined how time of day of neuropsychological testing influenced the performance of schizophrenic patients and healthy controls. All subjects were tested twice, once in the morning (AM) and once in the afternoon (PM), on a battery of neuropsychological tests. Testings were separated by 1week, and order of first testing (AM versus PM) was counterbalanced. Consistent with recent research, the current study found that time of day (TOD) influenced performance on most measures. However, the TOD effect differentially influenced the performance of each group. The controls showed better performance during PM (compared with AM) testings on measures of verbal memory and attention; whereas the patients showed better performance during PM (compared with AM) testings on measures of visual memory and motor speed. These results were not due to practice effects. Finally, there were trends for patient medication dosage to be associated with performance on some measures.