Serum homocysteine levels and cognitive functioning in euthymic bipolar patients

BACKGROUND: Studies have found elevated plasma homocysteine (Hcy) levels in bipolar disorder (BD). We investigated serum Hcy levels in euthymic BD patients, and its relationship with cognitive and psychosocial functioning. METHODS: Sixty-five BD type I euthymic patients and 49 healthy controls were assessed using a neuropsychological test battery. Hcy levels were measured using an HPLC method with fluorescence detection. RESULTS: The mean Hcy levels were 1.37 mg/L for BD patients and 1.30 mg/L for healthy controls (P=0.342), male patients showing higher Hcy levels as compared to females (P=0.009). Older patients, those with later illness onset, and patients taking more medications showed higher Hcy levels, but no significant correlation was found with psychosocial functioning. Patients with "elevated" Hcy levels performed significantly worse on all neurocognitive tests, and in patients we found significant associations between Hcy levels and number of perseverations on the SCT (r=0.248, P=0.047), and number of moves on the ToH (r=0.265, P=0.033); however, a linear regression model revealed that Hcy was not a significant predictor of neurocognitive test performance. CONCLUSIONS: Our findings suggest that increased homocysteinemia may play a role in the pathophysiology of neurocognitive deficits in BD, with a higher impact among older patients, or who had a delayed onset of illness.