Our findings on β‐endorphin and oxytocin are inconsistent with previous studies reporting higher plasma β‐endorphin levels in patients with schizophrenia (patient: n = 43, 77, and 49 vs control: n = 34, 74, 47),29, 30, 31 lower plasma oxytocin levels in patients with schizophrenia (patient: n = 34, 34, and 30 vs control: n = 31, 31, and 21),33, 34, 35 higher and lower plasma oxytocin levels in patients with BD II (patient: n = 135 and 25 vs control: n = 119 and 29),36, 37 and lower plasma oxytocin levels in patients with MDD (patient: n = 61 vs control: n = 60).38 Here, OXT is linked to major depressive disorder.