For example, PDHA1 (a PD causal protein) physically interacts with 15 psychiatric causal proteins; MAPT (another PD causal protein) physically interacts with 11 psychiatric causal proteins; LACTB (an AD causal protein) interacts with 10 psychiatric causal proteins; SCFD1 (an ALS causal protein) interacts with 9 psychiatric causal proteins; and CCDC6 and STX6 (AD causal proteins) each interacts with 7 psychiatric causal proteins, respectively (Fig. 6A, B; Table S8). Here, CCDC6 is linked to Parkinson disease.