There is evidence that, even in remission, patients with bipolar disorder (BD) have deficits in cognitive function and emotional regulation. Siblings of patients with BD are also reported to exhibit minor dysfunction in neuropsychological domains. In this study, we examined the interference of acute mood state with reaction time (RT) and response inhibition in euthymic patients with BD, in their healthy siblings and in healthy controls.

A total of 34 patients with bipolar I disorder, 22 healthy siblings and 33 healthy controls performed a stop-signal paradigm after induction of a transient intense sadness and a relaxed mood state. The differences in RT and the response inhibition were compared between the groups.

Euthymic patients with BD displayed a higher emotional reactivity compared with their siblings and with controls. Compared with controls, patients with BD showed longer RTs in a relaxed mood state and a delay in response inhibition during emotional activation.

The present study provides evidence for the clinical observation that patients with BD have shorter RTs when in a state of emotional arousal rather than in a relaxed state. Inhibitory deficits in these patients may be because of a too strong emotional arousal. The results show that in patients with BD, relaxation and emotional arousal are inversely associated with performance in a neuropsychological task. This is in contrast to findings in healthy individuals suggesting a dysbalance in emotional regulation in these patients.