Increased right amygdala volume in lithium-treated patients with bipolar I disorder

Objective: The amygdala plays a major role in processing emotional stimuli. Fourteen studies using structural magnetic resonance imaging (MRI) have examined the amygdala volume in paediatric and adult patients with bipolar disorder (BD) compared with healthy controls (HC) and reported inconsistent findings. Lithium has been found to increase grey matter volume, and first evidence points towards an effect on regional brain volume such as the amygdala. Method: We examined the amygdala volume of euthymic patients with BD treated with lithium (n = 15), without lithium (n = 24) and HC (n = 41) using structural MRI. Results: Patients treated with lithium exhibited in comparison to HC a larger right absolute (+17.9%, P = 0.015) and relative (+18%, P = 0.017) amygdala volume. There was no significant difference in amygdala volume between patients without lithium treatment and HC. Conclusion: Lithium appears to have a sustained effect on a central core region of emotional processing and should therefore be considered in studies examining BD.