Schizophrenia and bipolar disorder are disorders characterized by alterations in cellular and molecular mechanisms. Annexin A3 (ANXA3) has various effects on neural mechanisms and membrane phospholipid function and both mechanisms are thought to be associated with psychotic disorders. Our study consisted of 93 schizophrenia and bipolar disorder and 52 healthy controls. ANXA3 was analyzed by enzyme-linked immunosorbent assay (ELISA). ANXA3 levels were significantly different between the groups (p<0.001). ANXA3 levels of the control group were higher than ANXA3 levels of schizophrenia and bipolar disorder groups (p<0.001, p<0.001). The ANXA3 levels of the bipolar group were higher than the ANXA3 levels of the schizophrenia group (p<0.001). Laboratory levels of B12, folate, vitamin D, glucose, urea, creatinine, prothrombin time (PT), gamma-glutamyl transferase and lactate dehydrogenase were compared between the groups. B12 levels of the schizophrenia group were lower than B12 levels of bipolar and control groups (p=0.05, p<0.001). Creatinine levels of the schizophrenia group were higher than the creatinine levels of the healthy group (p<0.05). According to posthoc test results, PT levels of the schizophrenia group were higher than PT levels of the healthy group (p<0.05). In line with these findings, we suggest that ANXA3 protein deficiency may have an important role in the physiopathology of schizophrenia and bipolar disorder and may be used as a biomarker in the diagnosis of some psychotic disorders. [ABSTRACT FROM AUTHOR]