By Lucy Piper, Senior medwireNews Reporter
Compromised cognitive and adaptive functioning in euthymic patients with bipolar disorder may be partly explained by related comorbid anxiety, suggest researchers.
They studied autonomic nervous system arousal and cognitive functioning in such patients and found a heightened response to cognitive testing as well as lower cognitive test scores when compared with mentally healthy individuals.
"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," say Boaz Levy (University of Massachusetts, Boston, Maryland, USA) and team.
The researchers note that treating anxiety, particularly contextual anxiety that is triggered by cognitive demand in psychosocial settings, may therefore enhance the functional outcome of bipolar disorder patients.
As reported in Bipolar Disorders, they assessed autonomic nervous system arousal using an electrogram and skin electrodes in 30 euthymic patients with bipolar disorder and 22 mentally healthy individuals both before, at rest, and during a computerized neuropsychological battery (CNS Vital Signs).
Multivariate analysis showed a higher arousal on all physiological measures - finger temperature, galvanic skin response, and heart rate - for the bipolar disorder patients relative to controls before and during cognitive testing.
Also, the increase in physiological arousal from the restful state to the time of testing was significantly greater among bipolar disorder patients than controls.
Cognitive tests results indicated that except for IQ, bipolar disorder patients scored significantly lower than controls on all cognitive measures, including composite memory (average score 94.8 vs 103.0), attention (sustained=93.8 vs 106.6; complex=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).
The researchers note that the bipolar disorder patients reported significantly more mood symptoms and scored higher for trait anxiety than controls, and changes in autonomic nervous system arousal from baseline and trait anxiety correlated with most of the cognitive tests.
"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 [bipolar disorder]," they conclude.
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