TNF and bipolar disorder: TNF and its receptor TNFR1, have been suggested as plausible biomarkers for the prognosis and progression of schizophrenia and bipolar disorder, as increased soluble TNFR1 (sTNFR1) serum levels are found in acute patients (34,58); sTNFR1 is increased in treatment-resistant patients compared with nonresistant patients and healthy control participants (59).