A cluster consisting of alpha-2-macroglobulin, plasminogen activator inhibitor 1, prostatic acid phosphatase and serum glutamic oxaloacetic transaminase could distinguish schizophrenia from controls in both brain tissue and serum with a good precision (69% and 70%,respectively), but has a consistently low precision value in the case of distinguishing bipolar disorder from normal controls (<50% precision in both brain tissue and serum)(Figure 2A; Table S3b). Here, A2M is linked to bipolar disorder.