Serum brain-derived neurotrophic factor in euthymic bipolar patients on prophylactic lithium therapy.

AIM The aim of the study was to evaluate serum brain-derived neurotrophic factor (BDNF) levels in a group of euthymic bipolar patients on long-term prophylactic lithium treatment and to delineate putative relationships between lithium efficacy and BDNF concentrations. METHODS 141 euthymic bipolar patients (51 male, 90 female) on long-term lithium treatment were studied. Three categories of prophylactic lithium response were delineated: excellent lithium responders (ER; 30 patients), partial lithium responders (PR; 61 patients) and lithium nonresponders (NR; 50 patients). The control group consisted of 75 age- and gender-matched healthy subjects. RESULTS The lithium-treated patients as a whole group had lower BDNF levels compared to the healthy controls. However, after breaking down the patients into ER, PR and NR, it appeared that only NR had significantly lower BDNF levels compared with the healthy control subjects. No association between the age of the patients, duration of bipolar illness, and serum lithium and BDNF levels was found. CONCLUSION The results point to a relationship between lithium prophylactic efficacy and plasma BDNF levels in euthymic bipolar patients where lithium NR had reduced BDNF levels. These findings suggest that serum BDNF is associated with lithium efficacy in bipolar disorder.