Aim of the study:
We compared white blood cells parameters (total white blood cells (WBC), lymphocytes count (LYMPH#) and percentage (LYMPH%), monocytes count (MONO) and percentage (MONO%), basophils count (BASO#) and percentage (BASO%), eosinophils count (EO#) and percentage (EO%), neutrophils count (NEUT#) and percentage (NEUT%)) in patients with schizophrenia (SHZ), unipolar depression (UD) and bipolar disorder (BIP): bipolar depression (BD) and mania (BM).

Subject or material and methods:
This was a retrospective, cross-sectional, naturalistic study of 2381 patients (SHZ n=1244; UD n=794; BIP n=343, BD n=259, BM n=84). WBC as well as differential leukocytes count were measured using automated hematology analyzer.

Results:
There were significant differences between study groups (WBC, p=0.02; LYMPH# p=0.03; LYMPH% p=0.008; EO% p <0.001). Age and sex affected various white blood cells parameters.

Discussion:
Highest WBC was in the schizophrenia and bipolar mania groups, while patients with BM had lowest LYMPH%. Highest frequency of below or above normal WBC was found in patients with BM.

Conclusions:
There are differences in white blood cells between study groups.