Bipolar disorder is associated with neurocognitive impairment but the etiology of such impairment remains largely unknown. The present study aimed at investigating the performance of bipolar patients in various neuropsychological tasks within the framework of HPA axis hyperactivity model and also the impact of disease characteristics on neuropsychological functioning. Cognitive performance of 60 bipolar-I patients and 30 healthy controls was evaluated by using tasks from the CANTAB battery targeting visual memory, executive function and inhibitory control. Current symptoms were evaluated via administration of the Hamilton Depression Rating Scale (HAMD) and Young Mania Rating Scale (YMRS) whereas assessment of functioning was performed with the Global Assessment of Functioning (GAF). Basal cortisol levels were determined and all patients were administered the Dexamethasone Suppression Test (DST). Statistically significant differences between patients and controls were found in visuo-spatial associative learning and memory, planning, attentional set shifting and inhibitory control. Worse performance in visuospatial associative memory correlated with longer duration of illness and higher levels of basal cortisol. Poorer attentional set shifting was related to higher number of manic episodes. We found no relationship of neurocognitive measures with DST suppression status, current symptom severity or history of psychosis. The results of our study confirm the presence of cognitive deficits in bipolar disorder and provide evidence on the relation of cortisol with neuropsychological functioning, especially visuo-spatial associative memory. Moreover, we have found that number of previous manic episodes and duration of illness is associated with worse cognitive performance. It is known that neurocognitive deficits are evident in many patients with bipolar disorder. These deficits are often a cause of considerable distress and can lead to impairment of psychosocial and occupational functioning. The role of HPA axis needs to be further examined in bipolar disorder. Nevertheless, the identification of factors affecting neurocognitive functioning, like basal cortisol and number of manic episodes, may contribute to the implementation of more appropriate prevention strategies.

Key words: Bipolar disorder, HPA axis, cortisol, neurocognitive functioning, visual memory, executive function.

Κ. Τournikioti, D. Dikeos, Μ. Αlevizaki, Ι. Michopoulos, P. Ferentinos, Ε. Porichi, C.R. Soldatos, Α. Douzenis (page 199) 

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