Decreased serum zinc concentration during depressive episode in patients with bipolar disorder

•Serum zinc in bipolar I patients significantly decreased during depressive episode.•Serum zinc during mania/hypomania and in remission similar to healthy controls.•Serum zinc correlated positively with the number of manic relapses in the past year.•Serum zinc decreased in depression in the late stages of bipolar disorder.

ObjectivesZinc may be involved in the pathophysiology and treatment of depressive disorder. However, data on this issue in bipolar disorder (BD) are limited. The aim of the study was to assess zinc concentrations in the blood serum of patients at various phases and stages of bipolar disorder.MethodsThe study included 129 patients with a diagnosis of bipolar disorder type I (n=69) or type II (n=60). Fifty-eight were in a depressive episode, 23 in a manic episode and 48 in remission. Fifty healthy volunteers made a control group. Zinc concentration was measured using flame atomic absorption spectrometry.ResultsSerum zinc level in patients diagnosed with BD type I in the depressive phase was significantly reduced as compared with mania, remission and healthy subjects. In the BD type II, serum zinc level in hypomania, depression or remission phase was not significantly different from the control group. In the whole group, lower level of zinc in depression compared to remission and control subjects was found during late stage of the illness but not in the early stage. Zinc concentration was not dependent on the severity of manic or depressive symptoms and subtype of depression but correlated positively with the number of manic/hypomanic relapses in the past year.LimitationsLack of prospective model, heterogeneity of pharmacological treatment, small number of subgroups presenting specified clinical features.ConclusionsDecreased serum zinc concentration occurs in depression in BD type I and probably in depression in the late stage of BD.