It is hypothesized that the intranasal administration of insulin will enhance hippocampal-dependent neurocognitive performance in euthymic patients with bipolar I or II disorder. This novel initiative represents a proof-of-concept study that insulin is salient to neurocognitive functioning and deficits in bipolar disorder and represents a novel and safe therapeutic avenue. The available literature suggests that the acute administration of intranasal insulin enhances cognition in memory impaired older adults with either Alzheimer's disease or minimal cognitive impairment. Prior research demonstrates a cognitive enhancing effect of insulin within one hour of the first intranasal insulin dose. Other studies suggest that the long-term administration of intranasal insulin (i.e. over eight weeks) in enhances memory performance in human volunteers. We aim to evaluate the acute and long-term effects of intranasal insulin administration in persons with bipolar disorder. As such we will be conducting the neuropsychological testing at three time points, the week before receiving insulin, within one hour of the first dose and after 8 weeks of insulin administration.