Based on the results of three genome-wide cross-trait analysis with ASSET and CPASSOC, 12 shared genes (APOC4-APOC2, APOE, TOMM40, CLPTM1, PVRL2, CTB-179K24.3, BIN1, AP001257.1, CASS4, TMEM106B, PICALM, and SLC24A4) for comorbidity were identified for AD and all three stress-related psychiatric disorders, of which AP001257.1 is a novel gene that has never been reported in previous AD-related or the three stress-related psychiatric disorders. The gene discussed is APOC4; the disease is Alzheimer disease.