Lithium treatment effects on the neuropsychological functioning of patients with bipolar I disorder

To determine if medication plays a major role in cognitive impairment in bipolar disorder and if regular treatment with lithium influences the cognitive performance of a group of euthymic patients with bipolar I disorder.

Cognitive performance was assessed using neuropsychological tests of attention, memory, and executive function on 60 subjects: 20 euthymic bipolar I patients with no medication intake, 20 euthymic bipolar I patients who were following regular treatment with lithium carbonate monotherapy, and a third group of 20 control healthy subjects. The subjects were evaluated from January 2005 to October 2006. Patients were diagnosed using DSM-IV criteria for bipolar disorder.

Compared to the healthy group, bipolar I patients had significantly lower performance on episodic verbal and visual-verbal memory regardless of their medication status. No significant cognitive performance differences were found between the two groups of patients with bipolar disorder, suggesting that lithium therapy had no deleterious effects on cognition.

Patients with bipolar I disorder have verbal memory deficits that are not explained by medication or by lithium monotherapy, but by the condition itself.