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Influence of cognitive reserve on neuropsychological functioning in bipolar disorder: Findings from a 5-year longitudinal study

April 18, 2017

In February 2017, our research team published a paper on cognitive reserve in Bipolar Disorders. The authors are Kristin H. Hinrichs, Rebecca E. Easter, Kaley Angers, Bethany Pester, Zongshan Lai, David F. Marshall, Masoud Kamali, Melvin McInnis, Scott A. Langenecker, and Kelly A. Ryan.

Lead author Kristin H. Hinrichs explains this research:

Previous research suggests that bipolar disorder is often associated with cognitive difficulties, including decreased attention, memory, psychomotor speed, and executive functioning/problem solving skills. Because these cognitive skills are imperative for the safe management of everyday activities, it is important to understand how they develop and if they get worse over time. New studies are beginning to suggest that pre-existing factors, such as premorbid intellectual ability and education, may influence the presentation and severity of cognitive difficulties for individuals with neurological and psychiatric illness. These pre-existing factors, called “cognitive reserve,” are thought to be related to more efficient and stronger brain networks.

To explore the impact of cognitive reserve on neuropsychological difficulties and change over time, researchers from the Heinz C. Prechter Bipolar Research Fund comprehensively measured the cognitive abilities of individuals with bipolar disorder at two time points, five years apart. They found, consistent with previous research, that individuals with bipolar disorder obtained lower scores on measures of memory, attention, psychomotor speed, and executive functioning compared to controls. However, they found that the bipolar group did not differ from the control group in terms of the rate of change over time. These findings suggest that bipolar disorder does not lead to an accelerated rate of cognitive decline.

Results also suggest that high cognitive reserve is beneficial for individuals with bipolar disorder. Analyses found that higher intellectual ability was related to less cognitive change over time for the bipolar group. Further, lower intellectual ability and lower education were associated with decline on specific neuropsychological tests over time for the bipolar group. The same pattern was not found in the control group.

In summary, this new study showed that cognitive difficulties exist among many individuals with bipolar disorder, though there is generally a high degree of variability.  These deficits seem to be present early in the disorder, but do not progress at a more rapid rate than typical aging healthy adults.  Further, higher intellectual ability may selectively preserve cognitive abilities over time for individuals with bipolar disorder.