According to researchers of a new study, comorbid anxiety may be partially to blame for the compromised cognitive and adaptive functioning in euthymic patients with bipolar disorder. The team looked at such patients and studied their autonomic nervous system arousal and cognitive functioning, and discovered that, when compared to individuals with good mental wellness, patients with bipolar disorder showed a heightened response to cognitive testing as well as lower cognitive test scores.
According to the team from the University of Massachusetts in Boston, which was led by Boaz Levy, ‘Previous studies have provided support for a neuroprogressive model in BD [bipolar disorder]; however, it is quite possible that the etiological pathway leading to cognitive impairment in BD is complex, and compounded by acute symptoms related to anxiety.’
They went on to explain that treating anxiety, and contextual anxiety that is triggered by cognitive demand in psychosocial settings in particular, could therefore improve the mental wellbeing of bipolar disorder patients by helping to enhance their functional outcome.
For the study, which was published in Bipolar Disorders, the team used an electrogram and skin electrodes, to assess autonomic nervous system arousal in 30 euthymic patients with bipolar disorder and 22 individuals with good mental health. They did this before, at rest, and during a computerized neuropsychological battery (CNS Vital Signs).
Using multivariate analysis, the investigators found that on all physiological measures, including finger temperature, galvanic skin response, and heart rate, the bipolar disorder patients showed a higher arousal both before and during cognitive testing, in comparison to the control group. There was also a significantly greater increase in physiological arousal from the restful state to the time of testing among bipolar disorder patients than the controls.
When it came to cognitive measures, cognitive tests results indicated that except for IQ, bipolar disorder patients scored significantly lower than controls. This included composite memory (where the average score was 94.8 vs. 103.0), attention (in which sustained was 93.8 vs. 106.6 and complex was 95.5 vs. 105.7), processing speed (95.5 vs. 107.8), cognitive flexibility (94.8 vs. 109.0), and social acuity (95.6 vs. 104.5).
Levy’s team noted that the bipolar disorder patients also reported significantly more mood symptoms and scored higher for trait anxiety than controls, and there was a correlation between these changes in autonomic nervous system arousal from baseline and trait anxiety and most of the cognitive tests. This led them to conclude that, ‘The physiological reaction to chronic stress, which characterizes anxiety disorders, may explain the cognitive decline that accompanies a more severe course of illness in BD.’
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