A preliminary longitudinal study on the cognitive and functional outcome of bipolar excellent lithium responders.

Background: Neurocognitive dysfunction in bipolar disorder represents a possible marker of underlying pathophysiology, but to date, most studies are cross-sectional and heterogeneous with regard to pharmacological treatments. In the present study we investigated the 6-year cognitive and functional outcome of a sample of euthymic excellent lithium responders (ELR).

Method: A total sample of twenty subjects was assessed at baseline and 6years later: ten diagnosed of bipolar disorder according to DSM-IV criteria and ten healthy matched controls. The sample size was enough to find statistical differences between groups, with a statistical power of 0.8. Bipolar patients were on lithium treatment during all this follow-up period and fulfilled ELR criteria as measured by the Alda scale. A neuropsychological test battery tapping into the main cognitive domains was used at baseline and at after 6-year of follow-up. Functional outcome was evaluated by means of the Functioning Assessment Short Test at study endpoint.

Results: Repeated measures multivariate analyses of variance showed that bipolar patients were cognitively impaired in the executive functioning, inhibition, processing speed and verbal memory domains (p<0.03) compared to controls and such deficits were stable over time. Longer duration of illness and lower psychosocial outcome were significantly related to cognitive impairment (p<0.05).

Conclusions: Cognitive dysfunction was present even in euthymic ELR. These deficits remain stable over the long term, and are basically associated with greater symptoms and poorer psychosocial adjustment.