Objectives:
Some scientific reports indicate the changes in the concentration of serum copper in patients with bipolar disorder (BD), however the data are inconclusive. The aim of this study was to assess the concentration of copper in the blood serum of patients in various phases of BD compared to healthy volunteers, taking into consideration the specific clinical features, and the stage of illness.

Methods:
The study enrolled 133 patients with a diagnosis of BD (type I, II and NOS), including 61 people in depressive episode, 23 in mania or hypomania and 49 in remission. The control group consisted of 50 people. Atomic absorption spectrometry was used to measure the concentration of copper.

Results:
There were no statistically significant differences in the serum copper concentration between patients in various phases of BD (mania/hypomania, depression, remission), sub-types (Type I, Type II + NOS) or stages and healthy volunteers. However, serum copper concentrations in patients in stage 1 was significantly higher than in advanced stages (2+3+4), (ß = 0.22; p = 0.02). Serum copper concentration was also the higher, the later the age of onset was (ß = 0.33; p < 0.001), and the lower, the greater the number of illness episodes (ß = – 0.23; p = 0.02) (multiple regression model, adj R2 = 0.19, p = 0.0001).

Conclusions:
The dependencies demonstrated above may reflect pathophysiological processes that occur in the course of BD (e.g., inflammatory response and oxidative stress) with a different intensity depending on its stage.