High cognitive reserve in bipolar disorders as a moderator of neurocognitive impairment

Background: Cognitive reserve (CR) reflects the capacity of the brain to endure neuropathology, minimize clinical manifestations and successfully complete cognitive tasks. The present study aims to determine whether high CR may constitute a moderator of cognitive functioning in bipolar disorder (BD). Methods: 102 patients with BD and 32 healthy controls were enrolled. All patients met DSM-IV criteria for I or II BD and were euthymic (YMRS <= 6 and HDRS <= 8) during a 6-month period. All participants were tested with a comprehensive neuropsychological battery, and a Cerebral Reserve Score (CRS) was estimated. Subjects with a CRS below the group median were classified as having low CR, whereas participants with a CRS above the median value were considered to have high CR. Results: Participants with BD with high CR displayed a better performance in measures of attention (digits forward: F=4.554, p=0.039); phonemic and semantic verbal fluency (FAS: F=9.328, p=0.004; and Animal Naming: F=8.532, p=0.006); and verbal memory (short cued recall of California Verbal Learning Test: F=4.236, p=0.046), after multivariable adjustment for potential confounders, including number of admissions and prior psychotic symptoms. Limitations: The cross-sectional design of the study does not allow the establishment of causal inferences. Additionally, the small size of the sample may have limited some results. Conclusions: High cognitive reserve may therefore be a valuable construct to explore for predicting neurocognitive performance in patients with BD regarding premorbid status.