Abstract
Background Stress has a major impact on the onset and recurrence of mood episodes in bipolar disorder (BD) but the underlying mechanisms remains unknown. Previous studies have shown distinct time-dependent effects of stress on reward processing in healthy individuals. Impaired reward processing is a core characteristic of BD, and altered reward processing during recovery from stress could influence the development and course of bipolar disorder. Methods We investigated brain responses during reward processing 50 minutes after stress using fMRI in 40 healthy controls and 40 euthymic BD patients assigned to either an acute stress test (Trier Social Stress Test) or a no-stress condition. Results Acute stress increased cortisol levels in both healthy controls and BD patients. Ventral striatum responses to reward outcome were increased in healthy controls during stress recovery but not in BD patients. For anticipation, no differences were found between the groups following stress. Conclusions For the first time we show altered reward processing in BD patients during the recovery phase of stress. These data suggest reduced neural flexibility of hedonic signaling in response to environmental challenges. This may increase the susceptibility to stressful life events in the future and play a role in the development of further psychopathology on the longer term.
