SLC18A2 and post-traumatic stress disorder: The enrichment of genes involved in serotonin:sodium symporter activity (SLC6A4, SLC18A2), in serotonin binding (HTR2A, SLC6A4), and in peptide hormone binding (CRHR1, OXTR, CRHR2) once again highlight the potential impact of serotonin and peptide hormones in the pathophysiology of PTSD.